progress, still some TODO's before we can start running instructions. need to finish up the initial IO/mem then port the old assembler to DSAv2

dsa-emu/Cargo.toml

@@ -22,7 +22,7 @@ name = "bench_mainstore"
 harness = false
 
 [features]
-default = ["mainstore-bulkalloc", "mainstore-arraymap"]
+default = ["mainstore-bulkalloc"]
 
 # Memory Bank Features
 mainstore-bulkalloc = [] # Fastest for Writes

dsa-emu/benches/bench_mainstore.rs

@@ -4,7 +4,7 @@ use criterion::{
 };
 use std::time::Duration;
 
-use dsa::RandomAccessMemory;
+use dsa::{Page, RandomAccessMemory};
 
 type PhysAddr = u32;
 
@@ -139,7 +139,7 @@ fn run_write_page(
     addrs: &[PhysAddr],
     implementations: &mut [(&str, Box<dyn RandomAccessMemory>)],
 ) {
-    let page_data = [0xABu8; 4096];
+    let page_data = Page::from([0xABu8; 4096]);
     group.throughput(Throughput::Bytes(addrs.len() as u64 * 4096));
     for (name, mem) in implementations.iter_mut() {
         group.bench_with_input(BenchmarkId::new(*name, ""), addrs, |b, addrs| {

dsa-emu/config/dsa.iomap.ron

@@ -0,0 +1,7 @@
+[
+    IoMapping(
+        device: Display,
+        base: 0x0000_0000,
+        size: 0x0000_07D0, // 2000 bytes (80x25)
+    ),
+],

dsa-emu/src/args.rs

@@ -1,8 +1,9 @@
 use std::{fs, path::PathBuf};
 
 use clap::{Parser, ValueEnum};
+use serde::{Deserialize, Serialize};
 
-use crate::{MemoryMap, RandomAccessMemory};
+use crate::{MemoryMap, RandomAccessMemory, config::IoMapping, io::DeviceId};
 
 #[derive(Parser, Debug)]
 #[command(version, about, long_about = None)]
@@ -12,17 +13,38 @@ pub struct DsaArgs {
     #[arg(long = "mmap")]
     memory_map: Option<PathBuf>,
 
+    #[arg(long = "iomap")]
+    io_map: Option<PathBuf>,
+
     #[arg(value_enum, long = "mem", default_value = "bulk-alloc")]
     pub memory_bank: MemoryBank,
 }
 
 impl DsaArgs {
-    pub fn get_memory_map(&self) -> Option<MemoryMap> {
-        self.memory_map.as_ref().and_then(|m| {
+    pub fn get_memory_map(&self) -> MemoryMap {
+        self.memory_map
+            .as_ref()
+            .and_then(|m| {
                 fs::read_to_string(m)
                     .ok()
                     .and_then(|map| ron::from_str(&map).ok())
             })
+            .unwrap_or_else(|| {
+                ron::from_str(include_str!("./config/default/dsa.mmap.ron")).unwrap()
+            })
+    }
+
+    pub fn get_io_map(&self) -> Vec<IoMapping> {
+        self.io_map
+            .as_ref()
+            .and_then(|m| {
+                fs::read_to_string(m)
+                    .ok()
+                    .and_then(|map| ron::from_str(&map).ok())
+            })
+            .unwrap_or_else(|| {
+                ron::from_str(include_str!("./config/default/dsa.iomap.ron")).unwrap()
+            })
     }
 }
 

dsa-emu/src/config/default/dsa.iomap.ron

@@ -0,0 +1,7 @@
+[
+    IoMapping(
+        device: Display,
+        base: 0x0000_0000,
+        size: 0x0000_07D0, // 2000 bytes (80x25)
+    ),
+]

dsa-emu/src/config/mod.rs

@@ -0,0 +1,80 @@
+use serde::{Deserialize, Serialize};
+
+use crate::{
+    Emulator, RandomAccessMemory,
+    io::DeviceId,
+    memory::{PhysAddr, mmu::MMU},
+};
+
+#[repr(u32)]
+#[derive(Serialize, Deserialize, Clone, Copy, Debug)]
+pub enum RegionType {
+    Reserved,
+    Bootloader,
+    Kernel,
+    KernelTables,
+    Usable,
+    MMIO,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, Copy)]
+pub struct Region {
+    pub base: PhysAddr,
+    pub size: u32,
+    pub region_type: RegionType,
+
+    // flags for the emulator
+    #[serde(default)]
+    identity_map_on_boot: bool,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone)]
+pub struct MemoryMap {
+    table_addr: PhysAddr,
+    pub regions: Vec<Region>,
+}
+
+#[derive(Serialize, Deserialize)]
+pub struct IoMapping {
+    pub device: DeviceId,
+    pub base: u32,
+    pub size: u32,
+}
+
+impl MemoryMap {
+    pub const DEFAULT_MEMORY_MAP_ADDR: PhysAddr = 0x1000;
+
+    pub fn new() -> Self {
+        MemoryMap {
+            table_addr: Self::DEFAULT_MEMORY_MAP_ADDR,
+            regions: Vec::new(),
+        }
+    }
+
+    pub fn apply(&self, cpu: &mut Emulator<impl RandomAccessMemory>) {
+        for reg in &self.regions {
+            if reg.identity_map_on_boot {
+                Self::identity_map(cpu.mmu_mut(), reg);
+            }
+        }
+
+        let mem = cpu.memory_mut();
+        let mut offset = self.table_addr;
+        for region in &self.regions {
+            println!("Wrote entry: {region:?} to page table");
+            mem.write_word(offset, region.base);
+            mem.write_word(offset + 4, region.size);
+            mem.write_word(offset + 8, region.region_type as u32);
+            offset += 12;
+        }
+    }
+
+    pub fn identity_map(mmu: &mut MMU, region: &Region) {
+        let first_page = region.base >> 12;
+        let page_count = region.size >> 12;
+
+        for page in (first_page..first_page + page_count).map(|p| p << 12) {
+            mmu.create_mapping(page, page);
+        }
+    }
+}

dsa-emu/src/io/display.rs

@@ -0,0 +1,77 @@
+use std::sync::{
+    Arc,
+    atomic::{AtomicBool, AtomicU8, Ordering},
+};
+
+use crate::io::{IoAccess, IoDevice};
+
+pub struct DisplayDevice {
+    buffer: Arc<Box<[AtomicU8]>>,
+    dirty: Arc<AtomicBool>,
+}
+
+impl DisplayDevice {
+    pub fn new(width: usize, height: usize) -> (Self, DisplayHandle) {
+        let buffer = Arc::new(
+            (0..width * height)
+                .map(|_| AtomicU8::new(0))
+                .collect::<Vec<_>>()
+                .into_boxed_slice(),
+        );
+        let dirty = Arc::new(AtomicBool::new(false));
+
+        let handle = DisplayHandle {
+            buffer: Arc::clone(&buffer),
+            dirty: Arc::clone(&dirty),
+        };
+
+        (Self { buffer, dirty }, handle)
+    }
+}
+
+impl IoDevice for DisplayDevice {
+    fn size(&self) -> u32 {
+        (self.buffer.len()) as u32
+    }
+    fn access(&self) -> IoAccess {
+        IoAccess::WriteOnly
+    }
+
+    fn id(&self) -> super::DeviceId {
+        super::DeviceId::Display
+    }
+
+    fn write_word(&mut self, offset: u32, val: u32) -> bool {
+        let bytes = val.to_le_bytes();
+        self.buffer[offset as usize].store(bytes[0], Ordering::Relaxed);
+        self.buffer[offset as usize + 1].store(bytes[1], Ordering::Relaxed);
+        self.buffer[offset as usize + 2].store(bytes[2], Ordering::Relaxed);
+        self.buffer[offset as usize + 3].store(bytes[3], Ordering::Relaxed);
+        self.dirty.store(true, Ordering::Relaxed);
+        true
+    }
+
+    fn write_byte(&mut self, offset: u32, val: u8) -> bool {
+        self.buffer[offset as usize].store(val, Ordering::Relaxed);
+        self.dirty.store(true, Ordering::Relaxed);
+        true
+    }
+}
+
+pub struct DisplayHandle {
+    pub buffer: Arc<Box<[AtomicU8]>>,
+    pub dirty: Arc<AtomicBool>,
+}
+
+impl DisplayHandle {
+    pub fn is_dirty(&self) -> bool {
+        self.dirty.swap(false, Ordering::Relaxed)
+    }
+
+    pub fn read_all(&self) -> Vec<u8> {
+        self.buffer
+            .iter()
+            .map(|b| b.load(Ordering::Relaxed))
+            .collect()
+    }
+}

dsa-emu/src/io/mod.rs

@@ -0,0 +1,106 @@
+use serde::{Deserialize, Serialize};
+
+use crate::RandomAccessMemory;
+
+pub mod display;
+
+pub struct MappedDevice {
+    pub base: u32,
+    pub device: Box<dyn IoDevice>,
+}
+
+pub enum IoAccess {
+    ReadOnly,
+    WriteOnly,
+    ReadWrite,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum DeviceId {
+    Display,
+    Serial,
+    Random,
+    Timer,
+}
+
+/// Trait representing an input/output device that can be mapped into a memory space.
+///
+/// - Default methods return dummy data.
+pub trait IoDevice: Send {
+    /// Return the size (in bytes) of the device's addressable region.
+    fn size(&self) -> u32;
+
+    /// Return the access permissions for the device.
+    fn access(&self) -> IoAccess;
+
+    /// Return the DeviceId
+    fn id(&self) -> DeviceId;
+
+    #[inline]
+    /// Read a single byte from the specified address.
+    ///
+    /// By default, write‑only devices return `None`.  All other devices
+    /// return `Some(0)` as placeholder data.  Implementations should override
+    /// this method to provide actual read logic.
+    fn read_byte(&self, offset: u32) -> Option<u8> {
+        match self.access() {
+            IoAccess::WriteOnly => None,
+            _ => Some(0),
+        }
+    }
+
+    #[inline]
+    /// Write a single byte to the specified address.
+    ///
+    /// By default, read‑only devices return `false` indicating failure.
+    /// All other devices return `true`.  Implementations should override
+    /// this method to perform real write operations and return whether
+    /// the operation succeeded.
+    fn write_byte(&mut self, offset: u32, val: u8) -> bool {
+        match self.access() {
+            IoAccess::ReadOnly => false,
+            _ => true,
+        }
+    }
+
+    /// Read a 32‑bit word from the specified address in little‑endian order.
+    ///
+    /// The default implementation composes four consecutive byte reads using
+    /// `read_byte`.  If any byte read fails, the whole operation returns `None`.
+    /// Write‑only devices return `None` immediately.  Override this method for
+    /// more efficient word reads.
+    #[inline]
+    fn read_word(&self, offset: u32) -> Option<u32> {
+        match self.access() {
+            IoAccess::WriteOnly => None,
+            _ => {
+                // default: compose from bytes
+                let b0 = self.read_byte(offset)? as u32;
+                let b1 = self.read_byte(offset + 1)? as u32;
+                let b2 = self.read_byte(offset + 2)? as u32;
+                let b3 = self.read_byte(offset + 3)? as u32;
+                Some(b0 | b1 << 8 | b2 << 16 | b3 << 24)
+            }
+        }
+    }
+
+    /// Write a 32‑bit word to the specified address in little‑endian order.
+    ///
+    /// The default implementation splits the value into bytes and writes each
+    /// using `write_byte`.  Read‑only devices return `false`; otherwise returns
+    /// `true` after attempting all byte writes.  Override for more efficient
+    /// word writes or to handle partial failures.
+    fn write_word(&mut self, offset: u32, val: u32) -> bool {
+        match self.access() {
+            IoAccess::ReadOnly => false,
+            _ => {
+                let bytes = val.to_le_bytes();
+                self.write_byte(offset, bytes[0]);
+                self.write_byte(offset + 1, bytes[1]);
+                self.write_byte(offset + 2, bytes[2]);
+                self.write_byte(offset + 3, bytes[3]);
+                true
+            }
+        }
+    }
+}

dsa-emu/src/lib.rs

@@ -1,11 +1,12 @@
 #![feature(likely_unlikely)]
-#![feature(ptr_as_ref_unchecked)]
 
 pub mod args;
 mod common;
+pub mod config;
+pub mod io;
 mod memory;
 mod processor;
 
-pub use {memory::MemoryMap, processor::processor::Emulator, processor::state::SharedState};
+pub use {config::MemoryMap, processor::processor::Emulator, processor::state::SharedState};
 
 pub use memory::ram::*;

dsa-emu/src/main.rs

@@ -1,32 +1,54 @@
 use clap::Parser;
-use dsa::{BulkAllocStore, Emulator, MemoryMap, SharedState, args::DsaArgs};
+use dsa::{
+    BulkAllocStore, Emulator, MemoryMap, SharedState,
+    args::DsaArgs,
+    io::display::{DisplayDevice, DisplayHandle},
+};
 use std::{sync::Arc, thread};
 
 fn main() {
     let args = DsaArgs::parse();
 
-    let mut emulator = Emulator::new(BulkAllocStore::new());
-    emulator.apply_memory_map(args.get_memory_map().unwrap_or_default());
+    let mmap = args.get_memory_map();
+    let iomap = args.get_io_map();
+
+    let store = BulkAllocStore::new();
+    let (display, handle) = DisplayDevice::new(80, 25);
+
+    let mut emulator = Emulator::new(store)
+        .with_device(display)
+        .apply_memory_map(mmap)
+        .apply_io_map(iomap)
+        .unwrap();
 
     let state = emulator.state_handle();
 
     const STACK_SIZE: usize = 1024 * 1024 * 16;
     let runner = thread::Builder::new()
         .stack_size(STACK_SIZE)
-        .spawn(move || emulator.run())
+        .spawn(move || emulator.run().unwrap())
         .unwrap();
 
-    let observer = thread::spawn(|| observe(state));
+    let observer = thread::spawn(|| observe(state, handle));
 
     runner.join().unwrap();
     observer.join().unwrap();
 }
 
 /// todo: remove this!
-fn observe(state: Arc<SharedState>) {
+fn observe(state: Arc<SharedState>, handle: DisplayHandle) {
     loop {
         thread::sleep(std::time::Duration::from_millis(100));
         let state = state.proc.load();
         println!("GP Registers: {:?}", state.registers);
+
+        if handle.is_dirty() {
+            for line in handle.read_all().chunks(80) {
+                for (i, byte) in line.iter().enumerate() {
+                    print!("{}", *byte as char);
+                }
+                println!();
+            }
+        }
     }
 }

dsa-emu/src/memory/mod.rs

@@ -13,75 +13,3 @@ pub type PhysAddr = u32;
 pub enum FaultInfo {
     PageFault,
 }
-
-#[repr(u32)]
-#[derive(Serialize, Deserialize, Clone, Copy, Debug)]
-enum RegionType {
-    Reserved,
-    Bootloader,
-    Kernel,
-    KernelTables,
-    Usable,
-    MMIO,
-}
-
-#[derive(Serialize, Deserialize, Debug, Clone, Copy)]
-pub struct Region {
-    base: PhysAddr,
-    size: u32,
-    region_type: RegionType,
-
-    // flags for the emulator
-    #[serde(default)]
-    identity_map_on_boot: bool,
-}
-
-#[derive(Serialize, Deserialize, Debug, Clone)]
-pub struct MemoryMap {
-    table_addr: PhysAddr,
-    pub regions: Vec<Region>,
-}
-
-impl MemoryMap {
-    pub const DEFAULT_MEMORY_MAP_ADDR: PhysAddr = 0x1000;
-
-    pub fn new() -> Self {
-        MemoryMap {
-            table_addr: Self::DEFAULT_MEMORY_MAP_ADDR,
-            regions: Vec::new(),
-        }
-    }
-
-    pub fn apply(&self, cpu: &mut Emulator<impl RandomAccessMemory>) {
-        for reg in &self.regions {
-            if reg.identity_map_on_boot {
-                Self::identity_map(cpu.mmu_mut(), reg);
-            }
-        }
-
-        let mem = cpu.memory_mut();
-        let mut offset = self.table_addr;
-        for region in &self.regions {
-            println!("Wrote entry: {region:?} to page table");
-            mem.write_word(offset, region.base);
-            mem.write_word(offset + 4, region.size);
-            mem.write_word(offset + 8, region.region_type as u32);
-            offset += 12;
-        }
-    }
-
-    pub fn identity_map(mmu: &mut MMU, region: &Region) {
-        let first_page = region.base >> 12;
-        let page_count = (region.size >> 12);
-
-        for page in (first_page..first_page + page_count).map(|p| p << 12) {
-            mmu.create_mapping(page, page);
-        }
-    }
-}
-
-impl Default for MemoryMap {
-    fn default() -> Self {
-        ron::from_str(include_str!("../config/dsa.mmap.default.ron")).unwrap()
-    }
-}

dsa-emu/src/memory/ram/arraymap.rs

@@ -55,15 +55,15 @@ impl RandomAccessMemory for ArrayStore {
     }
 
     #[inline(always)]
-    fn read_page(&self, addr: PhysAddr) -> &[u8; 4096] {
+    fn read_page(&self, addr: PhysAddr) -> &Page {
         debug_assert_eq!(addr % 4096, 0);
         let (idx, _) = idx(addr);
 
         if likely(!self.pages[idx].is_null()) {
-            return unsafe { &*(self.pages[idx] as *const [u8; 4096]) };
+            return unsafe { &*(self.pages[idx] as *const Page) };
         }
 
-        return &[0; 4096];
+        return &Page([0; 4096]);
     }
 
     #[inline(always)]
@@ -92,7 +92,7 @@ impl RandomAccessMemory for ArrayStore {
     }
 
     #[inline(always)]
-    fn write_page(&mut self, addr: PhysAddr, value: &[u8; 4096]) {
+    fn write_page(&mut self, addr: PhysAddr, value: &Page) {
         debug_assert_eq!(addr % 4096, 0);
         let (idx, _) = idx(addr);
 
@@ -100,6 +100,8 @@ impl RandomAccessMemory for ArrayStore {
             self.pages[idx] = self.alloc();
         }
 
-        unsafe { (self.pages[idx] as *mut [u8; 4096]).write(*value) }
+        unsafe {
+            (self.pages[idx] as *mut Page).copy_from(value, 1);
+        }
     }
 }

dsa-emu/src/memory/ram/bulkalloc.rs

@@ -82,15 +82,15 @@ impl RandomAccessMemory for BulkAllocStore {
     }
 
     #[inline(always)]
-    fn read_page(&self, addr: PhysAddr) -> &[u8; 4096] {
+    fn read_page(&self, addr: PhysAddr) -> &Page {
         debug_assert_eq!(addr % 4096, 0);
         let (idx, _) = idx(addr);
 
         if likely(!self.pages[idx].is_null()) {
-            return unsafe { &*(self.pages[idx] as *const [u8; 4096]) };
+            return unsafe { &*(self.pages[idx] as *const Page) };
         }
 
-        return &[0; 4096];
+        return &Page::ZERO;
     }
 
     #[inline(always)]
@@ -119,7 +119,7 @@ impl RandomAccessMemory for BulkAllocStore {
     }
 
     #[inline(always)]
-    fn write_page(&mut self, addr: PhysAddr, value: &[u8; 4096]) {
+    fn write_page(&mut self, addr: PhysAddr, value: &Page) {
         debug_assert_eq!(addr % 4096, 0);
         let (idx, _) = idx(addr);
 
@@ -127,6 +127,8 @@ impl RandomAccessMemory for BulkAllocStore {
             self.pages[idx] = self.alloc();
         }
 
-        unsafe { (self.pages[idx] as *mut [u8; 4096]).write(*value) }
+        unsafe {
+            (self.pages[idx] as *mut Page).copy_from(value, 1);
+        }
     }
 }

dsa-emu/src/memory/ram/hashmap.rs

@@ -23,41 +23,44 @@ impl RandomAccessMemory for HashStore {
     #[inline(always)]
     fn read_byte(&self, addr: PhysAddr) -> u8 {
         let (page, offset) = Self::segment_addr(addr);
-        self.pages.get(&page).map(|p| p[offset]).unwrap_or(0)
+        self.pages
+            .get(&page)
+            .map(|p| p.as_ref()[offset])
+            .unwrap_or(0)
     }
 
     #[inline(always)]
     fn read_word(&self, addr: PhysAddr) -> u32 {
         let (page, offset) = Self::segment_addr(addr);
         debug_assert_eq!(offset % 4, 0);
-        let page = self.pages.get(&page).unwrap_or(&[0; 4096]);
+        let page = self.pages.get(&page).unwrap_or(&Page::ZERO);
         u32::from_be_bytes(page[offset..=offset + 3].try_into().unwrap())
     }
 
     #[inline(always)]
-    fn read_page(&self, addr: PhysAddr) -> &[u8; 4096] {
+    fn read_page(&self, addr: PhysAddr) -> &Page {
         debug_assert_eq!(addr % 0x1000, 0);
-        self.pages.get(&addr).unwrap_or(&[0; 4096])
+        self.pages.get(&addr).unwrap_or(&Page::ZERO)
     }
 
     #[inline(always)]
     fn write_byte(&mut self, addr: PhysAddr, value: u8) {
         let (page, offset) = Self::segment_addr(addr);
-        self.pages.entry(page).or_insert_with(|| [0; 4096])[offset] = value;
+        self.pages.entry(page).or_insert_with(|| Page::zeroed())[offset] = value;
     }
 
     #[inline(always)]
     fn write_word(&mut self, addr: PhysAddr, value: u32) {
         let (page, offset) = Self::segment_addr(addr);
         debug_assert_eq!(offset % 4, 0);
-        let page = self.pages.entry(page).or_insert_with(|| [0; 4096]);
+        let page = self.pages.entry(page).or_insert_with(|| Page::zeroed());
         page[offset..=offset + 3].copy_from_slice(&value.to_be_bytes());
     }
 
     #[inline(always)]
-    fn write_page(&mut self, addr: PhysAddr, value: &[u8; 4096]) {
+    fn write_page(&mut self, addr: PhysAddr, value: &Page) {
         debug_assert_eq!(addr % 0x1000, 0);
-        let page = self.pages.entry(addr).or_insert_with(|| [0; 4096]);
-        page.copy_from_slice(value);
+        let page = self.pages.entry(addr).or_insert_with(|| Page::zeroed());
+        page.0 = value.0;
     }
 }

dsa-emu/src/memory/ram/mod.rs

@@ -1,3 +1,5 @@
+use std::ops::{Deref, DerefMut};
+
 use crate::memory::PhysAddr;
 
 #[cfg(feature = "mainstore-arraymap")]
@@ -27,7 +29,37 @@ pub use prealloc::PreAllocStore;
 
 const NUM_PAGES: usize = 2 << 20;
 
-type Page = [u8; 4096];
+#[repr(transparent)]
+#[derive(Clone)]
+pub struct Page([u8; 4096]);
+
+impl Page {
+    pub const SIZE: usize = 4096;
+    pub const MASK: u32 = 0xFFF;
+    pub const ZERO: Self = Page::zeroed();
+
+    pub const fn zeroed() -> Self {
+        Self([0; 4096])
+    }
+
+    pub const fn from(data: [u8; 4096]) -> Self {
+        Self(data)
+    }
+}
+
+impl Deref for Page {
+    type Target = [u8];
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for Page {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
 
 #[inline(always)]
 const fn idx(addr: PhysAddr) -> (usize, usize) {
@@ -43,7 +75,7 @@ pub trait RandomAccessMemory {
 
     fn write_word(&mut self, addr: PhysAddr, value: u32);
 
-    fn read_page(&self, addr: PhysAddr) -> &[u8; 4096];
+    fn read_page(&self, addr: PhysAddr) -> &Page;
 
-    fn write_page(&mut self, addr: PhysAddr, value: &[u8; 4096]);
+    fn write_page(&mut self, addr: PhysAddr, value: &Page);
 }

dsa-emu/src/memory/ram/prealloc.rs

@@ -1,4 +1,7 @@
-use crate::memory::{PhysAddr, RandomAccessMemory, ram::NUM_PAGES};
+use crate::memory::{
+    PhysAddr, RandomAccessMemory,
+    ram::{NUM_PAGES, Page},
+};
 
 pub struct PreAllocStore {
     heap: Box<[u8; NUM_PAGES * 4096]>,
@@ -25,9 +28,9 @@ impl RandomAccessMemory for PreAllocStore {
     }
 
     #[inline(always)]
-    fn read_page(&self, addr: PhysAddr) -> &[u8; 4096] {
+    fn read_page(&self, addr: PhysAddr) -> &Page {
         debug_assert_eq!(addr % 4096, 0);
-        unsafe { (self.heap.as_ptr().add(addr as usize) as *const [u8; 4096]).as_ref_unchecked() }
+        unsafe { (self.heap.as_ptr().add(addr as usize) as *const Page).as_ref_unchecked() }
     }
 
     #[inline(always)]
@@ -41,7 +44,7 @@ impl RandomAccessMemory for PreAllocStore {
     }
 
     #[inline(always)]
-    fn write_page(&mut self, addr: PhysAddr, value: &[u8; 4096]) {
+    fn write_page(&mut self, addr: PhysAddr, value: &Page) {
         self.heap[addr as usize..addr as usize + 4096].copy_from_slice(value);
     }
 }

dsa-emu/src/memory/ram/stackarray.rs

@@ -53,15 +53,15 @@ impl RandomAccessMemory for StackArrayStore {
     }
 
     #[inline(always)]
-    fn read_page(&self, addr: PhysAddr) -> &[u8; 4096] {
+    fn read_page(&self, addr: PhysAddr) -> &Page {
         debug_assert_eq!(addr % 4096, 0);
         let (idx, _) = idx(addr);
 
         if likely(!self.pages[idx].is_null()) {
-            return unsafe { &*(self.pages[idx] as *const [u8; 4096]) };
+            return unsafe { &*(self.pages[idx] as *const Page) };
         }
 
-        return &[0; 4096];
+        return &Page::ZERO;
     }
 
     #[inline(always)]
@@ -90,7 +90,7 @@ impl RandomAccessMemory for StackArrayStore {
     }
 
     #[inline(always)]
-    fn write_page(&mut self, addr: PhysAddr, value: &[u8; 4096]) {
+    fn write_page(&mut self, addr: PhysAddr, value: &Page) {
         debug_assert_eq!(addr % 4096, 0);
         let (idx, _) = idx(addr);
 
@@ -98,6 +98,6 @@ impl RandomAccessMemory for StackArrayStore {
             self.pages[idx] = self.alloc();
         }
 
-        unsafe { (self.pages[idx] as *mut [u8; 4096]).write(*value) }
+        unsafe { (self.pages[idx] as *mut Page).copy_from(value, 1) }
     }
 }

dsa-emu/src/processor/interrupts.rs

@@ -1,5 +1,52 @@
+#[repr(u8)]
+#[derive(Clone, Copy)]
 pub enum Interrupt {
-    PageFault,
-    ProtectionFault,
-    Generic(u8),
+    // CPU exceptions 0-31
+    InvalidInterrupt = 0,
+    PageFault = 1,
+    ProtectionFault = 2,
+    InvalidOpcode = 3,
+    DivideByZero = 4,
+    StackOverflow = 5,
+    WriteToReadOnly = 6,
+    ReadFromWriteOnly = 7,
+    UnmappedIo = 8,
+    // 8-31 reserved for future CPU exceptions
+
+    // IRQ's (32-63)
+    Hardware(u8),
+
+    // Syscalls (64-255)
+    // OS defined, program uses INT 64-127
+    Software(u8) = 128,
+}
+
+impl Interrupt {
+    pub fn code(&self) -> u8 {
+        match self {
+            Interrupt::InvalidInterrupt => 0,
+            Interrupt::PageFault => 1,
+            Interrupt::ProtectionFault => 2,
+            Interrupt::InvalidOpcode => 3,
+            Interrupt::DivideByZero => 4,
+            Interrupt::StackOverflow => 5,
+            Interrupt::WriteToReadOnly => 6,
+            Interrupt::ReadFromWriteOnly => 7,
+            Interrupt::UnmappedIo => 8,
+            Interrupt::Hardware(x) => {
+                if *x < 32 || *x > 63 {
+                    0
+                } else {
+                    *x
+                }
+            }
+            Interrupt::Software(x) => {
+                if *x < 64 {
+                    0
+                } else {
+                    *x
+                }
+            }
+        }
+    }
 }

dsa-emu/src/processor/processor.rs

@@ -1,27 +1,44 @@
 use std::{
     hint::unlikely,
-    sync::{Arc, atomic::Ordering, mpsc},
-    thread,
+    sync::{
+        Arc,
+        atomic::Ordering,
+        mpsc::{self, TryRecvError},
+    },
     time::Duration,
 };
 
 use crate::{
+    Page,
     common::instructions::{InstructionWord, Opcode, Reg},
-    memory::{FaultInfo, MemoryMap, mmu::MMU, ram::RandomAccessMemory},
+    config::{IoMapping, MemoryMap, RegionType},
+    io::{IoDevice, MappedDevice},
+    memory::{mmu::MMU, ram::RandomAccessMemory},
     processor::{interrupts::Interrupt, state::SharedState},
 };
 
 pub struct Emulator<Mem: RandomAccessMemory> {
     internal_state: ProcessorSnapshot,
     shared_state: Arc<SharedState>,
+
+    // Interrupts
     interrupts: mpsc::Receiver<u8>,
+    pending_fault: Option<Interrupt>,
 
     // memory
     mmu: MMU,
     mainstore: Mem,
 
+    // IO
+    mmio: Vec<MappedDevice>,
+    mmio_region: Option<(u32, u32)>, // start end end of segment
+
     // optionals - not necessarily set on boot.
     memory_map: Option<MemoryMap>,
+
+    // Config params
+    __mmap_configured: bool,
+    __io_configured: bool,
 }
 
 unsafe impl<Mem: RandomAccessMemory> Send for Emulator<Mem> {}
@@ -31,14 +48,33 @@ impl<Mem: RandomAccessMemory> Emulator<Mem> {
 
         Self {
             interrupts: receiver,
+            pending_fault: None,
+
             internal_state: ProcessorSnapshot::default(),
             shared_state: Arc::new(SharedState::new(sender)),
+
+            memory_map: None,
             mmu: MMU::new(),
             mainstore: mem,
-            memory_map: None,
+
+            // mmio
+            mmio: Vec::new(),
+            mmio_region: None,
+
+            // Config params
+            __io_configured: false,
+            __mmap_configured: false,
         }
     }
 
+    pub fn with_device(mut self, device: impl IoDevice + 'static) -> Self {
+        self.mmio.push(MappedDevice {
+            base: 0,
+            device: Box::new(device),
+        });
+        self
+    }
+
     pub fn state_handle(&self) -> Arc<SharedState> {
         self.shared_state.clone()
     }
@@ -53,29 +89,6 @@ impl<Mem: RandomAccessMemory> Emulator<Mem> {
         &mut self.mainstore
     }
 
-    #[cold]
-    pub fn apply_memory_map(&mut self, map: MemoryMap) -> &mut Self {
-        map.apply(self);
-        self.memory_map = Some(map);
-        self
-    }
-
-    #[cold]
-    fn boot(&mut self) {
-        let regions = MemoryMap::default();
-        // self.mmu.paging_enabled(true);
-        MemoryMap::identity_map(&mut self.mmu, regions.regions.get(0).unwrap());
-
-        self.internal_state.running = true;
-    }
-
-    #[cold]
-    fn update(&mut self) {
-        self.shared_state
-            .proc
-            .store(Arc::new(self.internal_state.clone()));
-    }
-
     #[must_use]
     #[inline]
     pub fn reg(&self, reg: Reg) -> u32 {
@@ -98,6 +111,146 @@ impl<Mem: RandomAccessMemory> Emulator<Mem> {
         }
     }
 
+    #[cold]
+    pub fn apply_memory_map(mut self, map: MemoryMap) -> Self {
+        self.mmio_region = map
+            .regions
+            .iter()
+            .find(|r| matches!(r.region_type, RegionType::MMIO))
+            .map(|r| (r.base, r.base + r.size));
+
+        map.apply(&mut self);
+        self.memory_map = Some(map);
+        self.__mmap_configured = true;
+        self
+    }
+
+    pub fn apply_io_map(mut self, map: Vec<IoMapping>) -> Result<Self, String> {
+        if !self.__mmap_configured {
+            return Err("You must map memory before applying I/O mappings".to_string());
+        }
+
+        for entry in map {
+            if let Some(idx) = self.mmio.iter().position(|d| d.device.id() == entry.device) {
+                self.mmio[idx].base = entry.base;
+            } else {
+                eprintln!("WARN: no device registgered for {:?}", entry.device);
+            }
+        }
+
+        self.__io_configured = true;
+        Ok(self)
+    }
+
+    #[cold]
+    fn update(&mut self) {
+        self.shared_state
+            .proc
+            .store(Arc::new(self.internal_state.clone()));
+    }
+
+    #[cold]
+    fn boot(&mut self) -> Result<(), String> {
+        if !(self.__io_configured && self.__mmap_configured) {
+            return Err("Processor not configured".to_string());
+        }
+
+        if let Some(map) = &self.memory_map {
+            MemoryMap::identity_map(&mut self.mmu, map.regions.get(0).unwrap());
+        }
+
+        // self.mmu.paging_enabled(true);
+
+        self.internal_state.running = true;
+        Ok(())
+    }
+
+    #[cold]
+    fn shutdown(&mut self) {
+        self.internal_state.running = false;
+    }
+
+    #[cold]
+    pub fn idle_wait(&mut self) {
+        self.internal_state.running = false;
+
+        // Wait for an interrupt or state update to continue.
+        loop {
+            // Check for interrupts.
+            if let Ok(code) = self.interrupts.recv_timeout(Duration::from_millis(100)) {
+                self.interrupt(Interrupt::Software(code));
+                break;
+            }
+
+            // If we've received a request to continue running.
+            if self.shared_state.running.load(Ordering::Relaxed) {
+                break;
+            }
+
+            // UI requested a state update.
+            if self.shared_state.update_req.load(Ordering::Relaxed) {
+                self.update();
+            }
+        }
+
+        self.internal_state.running = true;
+    }
+
+    pub fn run(&mut self) -> Result<(), String> {
+        self.boot()?;
+
+        'emu: loop {
+            // Update UI thread (roughly every 512k cycles targeting UPS)
+            if unlikely(self.internal_state.clock & 0x7FFFF == 0) {
+                if self.shared_state.update_req.load(Ordering::Relaxed) {
+                    self.update();
+                }
+            }
+
+            // Check for commands or hardware Interrupts every 32k cycles
+            if self.internal_state.clock % 0x7FFF == 0 {
+                if self.shared_state.running.load(Ordering::Relaxed) == false {
+                    self.idle_wait();
+                }
+
+                match self.interrupts.try_recv() {
+                    Ok(code) => self.interrupt(Interrupt::Software(code)),
+                    Err(TryRecvError::Disconnected) => break 'emu,
+                    Err(TryRecvError::Empty) => {}
+                }
+            }
+
+            // let instruction = self.mmu.lookup(self.internal_state.reg(Reg::Pcx));
+            let pc = self.reg(Reg::Pcx);
+            let instruction = self.mem_read_word(pc);
+            self.execute(InstructionWord(instruction));
+
+            // Check if executing the interrupt caused a fault.
+            if let Some(fault) = self.pending_fault {
+                self.interrupt(fault);
+            }
+
+            // always increment clock.
+            self.internal_state.clock += 1;
+        }
+
+        self.shutdown();
+
+        Ok(())
+    }
+
+    #[inline]
+    fn interrupt(&mut self, int: Interrupt) {
+        let idt = self.reg(Reg::Idr);
+
+        *self.mut_reg(Reg::Spr) -= 4;
+        let spr = self.reg(Reg::Spr);
+        let pcx = self.reg(Reg::Pcx);
+        self.mem_write_word(spr, pcx);
+
+        *self.mut_reg(Reg::Pcx) = self.mem_read_word(idt + int.code() as u32 * 4)
+    }
+
     #[inline]
     fn execute(&mut self, word: InstructionWord) {
         match Opcode::from_u8(word.opcode()) {
@@ -118,44 +271,37 @@ impl<Mem: RandomAccessMemory> Emulator<Mem> {
             Some(Opcode::Ldbs) => todo!(),
             Some(Opcode::Ldhs) => todo!(),
             Some(Opcode::Ldb) => {
-                *self.mut_reg(word.dest()) = u32::from(
-                    self.mainstore
-                        .read_byte(self.reg(word.src1()) + word.imm16() as u32),
-                )
+                *self.mut_reg(word.dest()) =
+                    u32::from(self.mem_read_byte(self.reg(word.src1()) + word.imm16() as u32))
             }
             Some(Opcode::Ldh) => {
-                *self.mut_reg(word.dest()) = u32::from(
-                    self.mainstore
-                        .read_word(self.reg(word.src1()) + word.imm16() as u32)
-                        >> 16,
-                )
+                *self.mut_reg(word.dest()) =
+                    u32::from(self.mem_read_word(self.reg(word.src1()) + word.imm16() as u32) >> 16)
             }
             Some(Opcode::Ldw) => {
-                *self.mut_reg(word.dest()) = u32::from(
-                    self.mainstore
-                        .read_word(self.reg(word.src1()) + word.imm16() as u32),
-                )
+                *self.mut_reg(word.dest()) =
+                    u32::from(self.mem_read_word(self.reg(word.src1()) + word.imm16() as u32))
             }
 
             // store
             Some(Opcode::Stb) => {
-                self.mainstore.write_byte(
+                self.mem_write_byte(
                     self.reg(word.dest()) + word.imm16() as u32,
                     self.reg(word.src1()) as u8,
                 );
             }
             Some(Opcode::Sth) => {
-                self.mainstore.write_byte(
+                self.mem_write_byte(
                     self.reg(word.dest()) + word.imm16() as u32,
                     (self.reg(word.src1()) as u16 >> 8) as u8,
                 );
-                self.mainstore.write_byte(
+                self.mem_write_byte(
                     self.reg(word.dest()) + word.imm16() as u32 + 1,
                     self.reg(word.src1()) as u8,
                 );
             }
             Some(Opcode::Stw) => {
-                self.mainstore.write_word(
+                self.mem_write_word(
                     self.reg(word.dest()) + word.imm16() as u32,
                     self.reg(word.src1()),
                 );
@@ -260,71 +406,132 @@ impl<Mem: RandomAccessMemory> Emulator<Mem> {
             }
 
             Some(Opcode::Int) => {
-                self.interrupt(Interrupt::Generic(word.shamt()));
+                self.interrupt(Interrupt::Software(word.shamt()));
             }
             Some(Opcode::Hlt) => self.internal_state.running = false,
             None => {}
         }
     }
 
-    pub fn waiting(&mut self) {
-        self.internal_state.running = false;
-
-        // Wait for an interrupt or state update to continue.
-        loop {
-            // Check for interrupts.
-            if let Ok(code) = self.interrupts.recv_timeout(Duration::from_millis(100)) {
-                self.interrupt(Interrupt::Generic(code));
-                break;
+    #[inline]
+    fn mem_read_byte(&mut self, addr: u32) -> u8 {
+        if unlikely(self.is_mmio(addr)) {
+            return self.io_read_byte(addr);
+        }
+        self.mainstore.read_byte(addr)
     }
 
-            // UI requested a state update.
-            if self.shared_state.update_req.load(Ordering::Relaxed) {
-                self.update();
+    #[inline]
+    fn mem_write_byte(&mut self, addr: u32, val: u8) {
+        if unlikely(self.is_mmio(addr)) {
+            self.io_write_byte(addr, val);
+            return;
+        }
+        self.mainstore.write_byte(addr, val);
     }
 
-            // If we've received a request to continue running.
-            if self.shared_state.running.load(Ordering::Relaxed) {
-                break;
+    #[inline]
+    fn mem_read_word(&mut self, addr: u32) -> u32 {
+        if unlikely(self.is_mmio(addr)) {
+            return self.io_read_word(addr);
         }
+        self.mainstore.read_word(addr)
     }
 
-        self.internal_state.running = true;
+    #[inline]
+    fn mem_write_word(&mut self, addr: u32, val: u32) {
+        if unlikely(self.is_mmio(addr)) {
+            self.io_write_word(addr, val);
+            return;
+        }
+        self.mainstore.write_word(addr, val);
     }
 
-    pub fn run(&mut self) {
-        self.boot();
-
-        loop {
-            // Update UI thread (roughly every 512k cycles targeting UPS)
-            if unlikely(self.internal_state.clock & 0x7FFFF == 0) {
-                if self.shared_state.update_req.load(Ordering::Relaxed) {
-                    self.update();
+    #[inline]
+    fn mem_read_page(&mut self, addr: u32) -> &Page {
+        if unlikely(self.is_mmio(addr)) {
+            // pages spanning MMIO don't really make sense
+            // treat as fault
+            self.pending_fault = Some(Interrupt::ProtectionFault);
+            return &Page::ZERO;
         }
+        self.mainstore.read_page(addr)
     }
 
-            // Check for commands or hardware Interrupts every 32k cycles
-            if self.internal_state.clock % 0x7FFF == 0 {
-                if self.shared_state.running.load(Ordering::Relaxed) == false {
-                    self.waiting();
+    #[inline]
+    fn mem_write_page(&mut self, addr: u32, val: &Page) {
+        if unlikely(self.is_mmio(addr)) {
+            self.pending_fault = Some(Interrupt::ProtectionFault);
+            return;
+        }
+        self.mainstore.write_page(addr, val);
     }
 
-                if let Ok(code) = self.interrupts.try_recv() {
-                    self.interrupt(Interrupt::Generic(code));
-                }
+    // single MMIO check reused by all of the above
+    #[inline]
+    fn is_mmio(&self, addr: u32) -> bool {
+        self.mmio_region
+            .map(|(base, end)| addr >= base && addr < end)
+            .unwrap_or(false)
     }
 
-            // let instruction = self.mmu.lookup(self.internal_state.reg(Reg::Pcx));
-            let pc = self.reg(Reg::Pcx);
-            let instruction = self.memory_mut().read_word(pc);
-            self.execute(InstructionWord(instruction));
+    // --- cold IO paths ---
 
-            // always increment clock.
-            self.internal_state.clock += 1;
-        }
+    #[cold]
+    fn io_read_byte(&mut self, addr: u32) -> u8 {
+        // if let Some(device) = self.mmio.iter().find(|d| d.contains(addr)) {
+        //     match device.read_byte(addr) {
+        //         Some(val) => val,
+        //         None => {
+        //             self.pending_fault = Some(Interrupt::ReadFromWriteOnly);
+        //             0
+        //         }
+        //     }
+        // } else {
+        //     self.pending_fault = Some(Interrupt::UnmappedIo);
+        //     0
+        // }
+        todo!()
     }
 
-    fn interrupt(&mut self, int: Interrupt) {
+    #[cold]
+    fn io_read_word(&mut self, addr: u32) -> u32 {
+        // if let Some(device) = self.mmio.iter().find(|d| d.contains(addr)) {
+        //     match device.read_word(addr) {
+        //         Some(val) => val,
+        //         None => {
+        //             self.pending_fault = Some(Interrupt::ReadFromWriteOnly);
+        //             0
+        //         }
+        //     }
+        // } else {
+        //     self.pending_fault = Some(Interrupt::UnmappedIo);
+        //     0
+        // }
+        todo!()
+    }
+
+    #[cold]
+    fn io_write_byte(&mut self, addr: u32, val: u8) {
+        // if let Some(device) = self.mmio.iter_mut().find(|d| d.contains(addr)) {
+        //     if !device.write_byte(addr, val) {
+        //         self.pending_fault = Some(Interrupt::WriteToReadOnly);
+        //     }
+        // } else {
+        //     self.pending_fault = Some(Interrupt::UnmappedIo);
+        // }
+        todo!()
+    }
+
+    #[cold]
+    fn io_write_word(&mut self, addr: u32, val: u32) {
+        // if let Some(device) = self.mmio.iter_mut().find(|d| d.contains(addr)) {
+        //     if !device.write_word(addr, val) {
+        //         self.pending_fault = Some(Interrupt::WriteToReadOnly);
+        //     }
+        // } else {
+        //     self.pending_fault = Some(Interrupt::UnmappedIo);
+        // }
         todo!()
     }
 }

dsa-emu/src/processor/state.rs

@@ -1,8 +1,4 @@
-use std::sync::{
-    Arc,
-    atomic::{AtomicBool, AtomicU8},
-    mpsc,
-};
+use std::sync::{Arc, atomic::AtomicBool, mpsc};
 
 use crate::processor::processor::ProcessorSnapshot;
 use arc_swap::ArcSwap;