diff --git a/crates/fayalite/src/sim.rs b/crates/fayalite/src/sim.rs
index 009e599..3802ae4 100644
--- a/crates/fayalite/src/sim.rs
+++ b/crates/fayalite/src/sim.rs
@@ -16,6 +16,7 @@ use crate::{
     },
     int::BoolOrIntType,
     intern::{Intern, Interned, Memoize},
+    memory::PortKind,
     module::{
         transform::deduce_resets::deduce_resets, AnnotatedModuleIO, Block, Id, InstantiatedModule,
         ModuleBody, NameId, NormalModuleBody, ScopedNameId, Stmt, StmtConnect, StmtDeclaration,
@@ -28,9 +29,9 @@ use crate::{
             Insn, InsnField, InsnFieldKind, InsnFieldType, Insns, InsnsBuilding, InsnsBuildingDone,
             SlotDebugData, SmallUInt, State, StatePartArrayIndex, StatePartArrayIndexed,
             StatePartIndex, StatePartIndexRange, StatePartKind, StatePartKindBigSlots,
-            StatePartKindSmallSlots, StatePartLayout, StatePartLen, StatePartsValue,
-            TypeArrayIndex, TypeArrayIndexes, TypeIndex, TypeIndexRange, TypeLayout, TypeLen,
-            TypeParts,
+            StatePartKindMemories, StatePartKindSmallSlots, StatePartLayout, StatePartLen,
+            StatePartsValue, TypeArrayIndex, TypeArrayIndexes, TypeIndex, TypeIndexRange,
+            TypeLayout, TypeLen, TypeParts,
         },
         time::{SimDuration, SimInstant},
     },
@@ -136,7 +137,7 @@ impl<T: Type> CompiledTypeLayout<T> {
                             name: Interned::default(),
                             ty: *input,
                         };
-                        layout.big_slots = StatePartLayout::scalar(debug_data);
+                        layout.big_slots = StatePartLayout::scalar(debug_data, ());
                         CompiledTypeLayout {
                             ty: *input,
                             layout: layout.into(),
@@ -1163,14 +1164,20 @@ impl Assignment {
                     }
                     (
                         _,
-                        InsnFieldType::SmallUInt(_)
+                        InsnFieldType::Memory(_)
+                        | InsnFieldType::SmallUInt(_)
                         | InsnFieldType::SmallSInt(_)
                         | InsnFieldType::InternedBigInt(_)
                         | InsnFieldType::U8(_)
                         | InsnFieldType::USize(_)
                         | InsnFieldType::Empty(_),
                     )
-                    | (InsnFieldKind::Immediate | InsnFieldKind::BranchTarget, _) => {}
+                    | (
+                        InsnFieldKind::Immediate
+                        | InsnFieldKind::Memory
+                        | InsnFieldKind::BranchTarget,
+                        _,
+                    ) => {}
                 }
             }
         }
@@ -1207,6 +1214,20 @@ struct Register {
     source_location: SourceLocation,
 }
 
+#[derive(Debug)]
+enum MemoryPort {
+    ReadOnly {},
+    WriteOnly {},
+    ReadWrite {},
+}
+
+#[derive(Debug)]
+struct Memory {
+    mem: Mem,
+    memory: StatePartIndex<StatePartKindMemories>,
+    ports: Vec<MemoryPort>,
+}
+
 #[derive(Debug)]
 pub struct Compiler {
     insns: Insns<InsnsBuilding>,
@@ -1227,6 +1248,7 @@ pub struct Compiler {
     enum_discriminants: HashMap<CompiledValue<Enum>, StatePartIndex<StatePartKindSmallSlots>>,
     registers: Vec<Register>,
     traces: Vec<SimTrace<()>>,
+    memories: Vec<Memory>,
 }
 
 impl Compiler {
@@ -1251,6 +1273,7 @@ impl Compiler {
             enum_discriminants: HashMap::new(),
             registers: Vec::new(),
             traces: Vec::new(),
+            memories: Vec::new(),
         }
     }
     fn new_sim_trace(&mut self, kind: SimTraceKind) -> TraceScalarId {
@@ -1809,7 +1832,7 @@ impl Compiler {
                 let dest = self
                     .insns
                     .allocate_variable(&TypeLayout {
-                        small_slots: StatePartLayout::scalar(debug_data),
+                        small_slots: StatePartLayout::scalar(debug_data, ()),
                         big_slots: StatePartLayout::empty(),
                     })
                     .small_slots
@@ -1851,7 +1874,7 @@ impl Compiler {
                 let dest = self
                     .insns
                     .allocate_variable(&TypeLayout {
-                        small_slots: StatePartLayout::scalar(debug_data),
+                        small_slots: StatePartLayout::scalar(debug_data, ()),
                         big_slots: StatePartLayout::empty(),
                     })
                     .small_slots
@@ -3038,10 +3061,13 @@ impl Compiler {
                 .state_layout
                 .ty
                 .small_slots
-                .allocate(&StatePartLayout::scalar(SlotDebugData {
-                    name: Interned::default(),
-                    ty: Bool.canonical(),
-                }))
+                .allocate(&StatePartLayout::scalar(
+                    SlotDebugData {
+                        name: Interned::default(),
+                        ty: Bool.canonical(),
+                    },
+                    (),
+                ))
                 .start
         };
         let last_clk_was_low = alloc_small_slot("last_clk_was_low");
@@ -3098,10 +3124,13 @@ impl Compiler {
                 .state_layout
                 .ty
                 .small_slots
-                .allocate(&StatePartLayout::scalar(SlotDebugData {
-                    name: Interned::default(),
-                    ty: retval_ty.canonical(),
-                }))
+                .allocate(&StatePartLayout::scalar(
+                    SlotDebugData {
+                        name: Interned::default(),
+                        ty: retval_ty.canonical(),
+                    },
+                    (),
+                ))
                 .start;
             let discriminant_bit_width = enum_value.layout.ty.discriminant_bit_width();
             let discriminant_mask = !(!0u64 << discriminant_bit_width);
@@ -3289,6 +3318,49 @@ impl Compiler {
         }
         self.make_trace_decl(*parent_module, target_base)
     }
+    fn compile_memory(
+        &mut self,
+        mem: Mem,
+        instantiated_module: InstantiatedModule,
+        conditions: Interned<[Cond]>,
+        trace_decls: &mut Vec<TraceDecl>,
+    ) {
+        let memory = self
+            .insns
+            .state_layout
+            .memories
+            .allocate(&StatePartLayout::scalar(
+                (),
+                mem.initial_value().unwrap_or_else(|| {
+                    Intern::intern_owned(BitVec::repeat(
+                        false,
+                        mem.array_type().type_properties().bit_width,
+                    ))
+                }),
+            ))
+            .start;
+        let ports = mem
+            .ports()
+            .iter()
+            .map(|&port| {
+                let target_base = TargetBase::MemPort(port);
+                let target = TargetInInstantiatedModule {
+                    instantiated_module,
+                    target: target_base.into(),
+                };
+                self.decl_conditions.insert(target, conditions);
+                trace_decls.push(self.make_trace_decl(instantiated_module, target_base));
+                todo!("handle read/write");
+                match port.port_kind() {
+                    PortKind::ReadOnly => MemoryPort::ReadOnly {},
+                    PortKind::WriteOnly => MemoryPort::WriteOnly {},
+                    PortKind::ReadWrite => MemoryPort::ReadWrite {},
+                }
+            })
+            .collect();
+        self.memories.push(Memory { mem, memory, ports });
+        todo!("implement memory");
+    }
     fn compile_block(
         &mut self,
         parent_module: Interned<InstantiatedModule>,
@@ -3298,7 +3370,7 @@ impl Compiler {
     ) {
         let Block { memories, stmts } = block;
         for memory in memories {
-            todo!("implement memory");
+            self.compile_memory(memory, *parent_module, conditions, trace_decls);
         }
         for stmt in stmts {
             match stmt {
@@ -3613,11 +3685,17 @@ impl Compiler {
             }
         }
     }
+    fn process_memories(&mut self) {
+        for memory in mem::take(&mut self.memories) {
+            todo!();
+        }
+    }
     pub fn compile(mut self) -> Compiled<Bundle> {
         let base_module =
             *self.compile_module(InstantiatedModule::Base(self.base_module).intern_sized());
         self.process_assignments();
         self.process_registers();
+        self.process_memories();
         let clocks_triggered = self.process_clocks();
         self.insns
             .push(Insn::Return, self.base_module.source_location());
diff --git a/crates/fayalite/src/sim/interpreter.rs b/crates/fayalite/src/sim/interpreter.rs
index cb1f29b..0fd0591 100644
--- a/crates/fayalite/src/sim/interpreter.rs
+++ b/crates/fayalite/src/sim/interpreter.rs
@@ -2,15 +2,18 @@
 // See Notices.txt for copyright information
 
 use crate::{
+    int::{BoolOrIntType, SInt, UInt},
     intern::{Intern, Interned, Memoize},
     source_location::SourceLocation,
     ty::CanonicalType,
     util::get_many_mut,
 };
+use bitvec::{boxed::BitBox, slice::BitSlice};
 use hashbrown::HashMap;
 use num_bigint::BigInt;
 use num_traits::{One, Signed, ToPrimitive, Zero};
 use std::{
+    any::TypeId,
     borrow::BorrowMut,
     convert::Infallible,
     fmt,
@@ -28,6 +31,7 @@ pub(crate) const MIN_BITS_FOR_NEEDING_BIG: usize = SmallUInt::BITS as usize + 1;
 pub(crate) enum InsnFieldKind {
     Input,
     Output,
+    Memory,
     Immediate,
     BranchTarget,
 }
@@ -108,6 +112,7 @@ macro_rules! insn_field_enum {
 
 insn_field_enum! {
     pub(crate) enum InsnFieldType<Transform: InsnFieldTypeTransform> {
+        Memory(Transform::Type<StatePartIndex<StatePartKindMemories>>),
         SmallSlot(Transform::Type<StatePartIndex<StatePartKindSmallSlots>>),
         BigSlot(Transform::Type<StatePartIndex<StatePartKindBigSlots>>),
         SmallSlotArrayIndexed(Transform::Type<StatePartArrayIndexed<StatePartKindSmallSlots>>),
@@ -206,7 +211,8 @@ impl Insn {
                             continue;
                         }
                     }
-                    InsnFieldType::SmallSlot(_)
+                    InsnFieldType::Memory(_)
+                    | InsnFieldType::SmallSlot(_)
                     | InsnFieldType::BigSlot(_)
                     | InsnFieldType::SmallSlotArrayIndexed(_)
                     | InsnFieldType::BigSlotArrayIndexed(_)
@@ -216,9 +222,15 @@ impl Insn {
                     | InsnFieldType::U8(_)
                     | InsnFieldType::Empty(_) => {}
                 },
-                InsnFieldKind::Input | InsnFieldKind::Output | InsnFieldKind::Immediate => {}
+                InsnFieldKind::Input
+                | InsnFieldKind::Memory
+                | InsnFieldKind::Output
+                | InsnFieldKind::Immediate => {}
             }
             match field.ty {
+                InsnFieldType::Memory(v) => {
+                    v.debug_fmt(f, ",", " // ", "", state_layout)?;
+                }
                 InsnFieldType::SmallSlot(v) => {
                     v.debug_fmt(f, ",", " // ", "", state_layout)?;
                 }
@@ -577,9 +589,10 @@ pub(crate) trait StatePartKind:
 {
     const NAME: &'static str;
     type DebugData: Send + Sync + Eq + Hash + fmt::Debug + 'static + Copy;
+    type LayoutData: Send + Sync + Eq + Hash + fmt::Debug + 'static + Copy;
     type State: fmt::Debug + 'static + Clone;
     type BorrowedState<'a>: 'a;
-    fn new_state(len: StatePartLen<Self>) -> Self::State;
+    fn new_state(layout_data: &[Self::LayoutData]) -> Self::State;
     fn borrow_state<'a>(state: &'a mut Self::State) -> Self::BorrowedState<'a>;
     fn part_debug_data<BK: InsnsBuildingKind>(
         state_layout: &StateLayout<BK>,
@@ -950,8 +963,8 @@ macro_rules! make_state_part_kinds {
                 Self {
                     insns,
                     pc: 0,
-                    $($state_field: StatePart::new(insns.state_layout.$state_field.len()),)*
-                    $($type_field: StatePart::new(insns.state_layout.ty.$type_field.len()),)*
+                    $($state_field: StatePart::new(&insns.state_layout.$state_field.layout_data),)*
+                    $($type_field: StatePart::new(&insns.state_layout.ty.$type_field.layout_data),)*
                 }
             }
             pub(crate) fn borrow(&mut self) -> BorrowedState<'_> {
@@ -1150,10 +1163,11 @@ make_state_part_kinds! {
     impl StatePartKind for StatePartKindSmallStack {
         const NAME: &'static str = "SmallStack";
         type DebugData = ();
+        type LayoutData = ();
         type State = Stack<SmallUInt>;
         type BorrowedState<'a> = BorrowedStack<'a, SmallUInt>;
-        fn new_state(len: StatePartLen<Self>) -> Self::State {
-            Stack::new(len.value.try_into().expect("state is too big"))
+        fn new_state(layout_data: &[Self::LayoutData]) -> Self::State {
+            Stack::new(layout_data.len())
         }
         fn borrow_state<'a>(state: &'a mut Self::State) -> Self::BorrowedState<'a> {
             state.borrow()
@@ -1169,10 +1183,11 @@ make_state_part_kinds! {
     impl StatePartKind for StatePartKindBigStack {
         const NAME: &'static str = "BigStack";
         type DebugData = ();
+        type LayoutData = ();
         type State = Stack<BigInt>;
         type BorrowedState<'a> = BorrowedStack<'a, BigInt>;
-        fn new_state(len: StatePartLen<Self>) -> Self::State {
-            Stack::new(len.value.try_into().expect("state is too big"))
+        fn new_state(layout_data: &[Self::LayoutData]) -> Self::State {
+            Stack::new(layout_data.len())
         }
         fn borrow_state<'a>(state: &'a mut Self::State) -> Self::BorrowedState<'a> {
             state.borrow()
@@ -1184,14 +1199,35 @@ make_state_part_kinds! {
             state_layout.big_stack.debug_data.get(part_index.as_usize())
         }
     }*/
+    #[state, field = memories]
+    impl StatePartKind for StatePartKindMemories {
+        const NAME: &'static str = "Memories";
+        type DebugData = ();
+        type LayoutData = Interned<BitSlice>;
+        type State = Box<[BitBox]>;
+        type BorrowedState<'a> = &'a mut [BitBox];
+        fn new_state(layout_data: &[Self::LayoutData]) -> Self::State {
+            layout_data.iter().map(|initial_data| BitBox::from_bitslice(initial_data)).collect()
+        }
+        fn borrow_state<'a>(state: &'a mut Self::State) -> Self::BorrowedState<'a> {
+            state
+        }
+        fn part_debug_data<BK: InsnsBuildingKind>(
+            state_layout: &StateLayout<BK>,
+            part_index: StatePartIndex<Self>,
+        ) -> Option<&Self::DebugData> {
+            state_layout.memories.debug_data.get(part_index.as_usize())
+        }
+    }
     #[type, field = small_slots]
     impl StatePartKind for StatePartKindSmallSlots {
         const NAME: &'static str = "SmallSlots";
         type DebugData = SlotDebugData;
+        type LayoutData = ();
         type State = Box<[SmallUInt]>;
         type BorrowedState<'a> = &'a mut [SmallUInt];
-        fn new_state(len: StatePartLen<Self>) -> Self::State {
-            vec![0; len.value.try_into().expect("state is too big")].into_boxed_slice()
+        fn new_state(layout_data: &[Self::LayoutData]) -> Self::State {
+            vec![0; layout_data.len()].into_boxed_slice()
         }
         fn borrow_state<'a>(state: &'a mut Self::State) -> Self::BorrowedState<'a> {
             state
@@ -1207,10 +1243,11 @@ make_state_part_kinds! {
     impl StatePartKind for StatePartKindBigSlots {
         const NAME: &'static str = "BigSlots";
         type DebugData = SlotDebugData;
+        type LayoutData = ();
         type State = Box<[BigInt]>;
         type BorrowedState<'a> = &'a mut [BigInt];
-        fn new_state(len: StatePartLen<Self>) -> Self::State {
-            std::iter::repeat_with(BigInt::default).take(len.value.try_into().expect("state is too big")).collect()
+        fn new_state(layout_data: &[Self::LayoutData]) -> Self::State {
+            layout_data.iter().map(|_| BigInt::default()).collect()
         }
         fn borrow_state<'a>(state: &'a mut Self::State) -> Self::BorrowedState<'a> {
             state
@@ -1348,6 +1385,7 @@ impl<K: StatePartKind<DebugData = SlotDebugData>, BK: InsnsBuildingKind> StatePa
                 .iter()
                 .map(|v| v.with_prefixed_debug_names(prefix))
                 .collect(),
+            layout_data: self.layout_data.clone(),
             _phantom: PhantomData,
         }
     }
@@ -1358,6 +1396,7 @@ impl<K: StatePartKind<DebugData = SlotDebugData>, BK: InsnsBuildingKind> StatePa
                 .iter()
                 .map(|v| v.with_anonymized_debug_info())
                 .collect(),
+            layout_data: self.layout_data.clone(),
             _phantom: PhantomData,
         }
     }
@@ -1552,6 +1591,7 @@ impl<K: StatePartKind> fmt::Debug for StatePartLen<K> {
 #[derive(Clone, PartialEq, Eq, Hash)]
 pub(crate) struct StatePartLayout<K: StatePartKind, BK: InsnsBuildingKind> {
     pub(crate) debug_data: BK::Vec<K::DebugData>,
+    pub(crate) layout_data: BK::Vec<K::LayoutData>,
     pub(crate) _phantom: PhantomData<K>,
 }
 
@@ -1572,6 +1612,7 @@ impl<K: StatePartKind, BK: InsnsBuildingKind> StatePartLayout<K, BK> {
     pub(crate) fn empty() -> Self {
         Self {
             debug_data: Default::default(),
+            layout_data: Default::default(),
             _phantom: PhantomData,
         }
     }
@@ -1583,15 +1624,17 @@ impl<K: StatePartKind> From<StatePartLayout<K, InsnsBuilding>>
     fn from(value: StatePartLayout<K, InsnsBuilding>) -> Self {
         Self {
             debug_data: Intern::intern_owned(value.debug_data),
+            layout_data: Intern::intern_owned(value.layout_data),
             _phantom: PhantomData,
         }
     }
 }
 
 impl<K: StatePartKind> StatePartLayout<K, InsnsBuilding> {
-    pub(crate) fn scalar(debug_data: K::DebugData) -> Self {
+    pub(crate) fn scalar(debug_data: K::DebugData, layout_data: K::LayoutData) -> Self {
         Self {
             debug_data: vec![debug_data],
+            layout_data: vec![layout_data],
             _phantom: PhantomData,
         }
     }
@@ -1609,9 +1652,11 @@ impl<K: StatePartKind> StatePartLayout<K, InsnsBuilding> {
         let len = layout.len();
         let Self {
             debug_data,
+            layout_data,
             _phantom: _,
         } = self;
         debug_data.extend_from_slice(&layout.debug_data);
+        layout_data.extend_from_slice(&layout.layout_data);
         StatePartIndexRange { start, len }
     }
 }
@@ -1620,13 +1665,18 @@ impl<K: StatePartKind, BK: InsnsBuildingKind> fmt::Debug for StatePartLayout<K,
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let Self {
             debug_data,
+            layout_data,
             _phantom: _,
         } = self;
         write!(f, "StatePartAllocationLayout<{}>", K::NAME)?;
-        f.debug_struct("")
+        let mut debug_struct = f.debug_struct("");
+        debug_struct
             .field("len", &debug_data.len())
-            .field("debug_data", debug_data)
-            .finish_non_exhaustive()
+            .field("debug_data", debug_data);
+        if TypeId::of::<K::LayoutData>() != TypeId::of::<()>() {
+            debug_struct.field("layout_data", layout_data);
+        }
+        debug_struct.finish_non_exhaustive()
     }
 }
 
@@ -1723,9 +1773,9 @@ pub(crate) struct StatePart<K: StatePartKind> {
 }
 
 impl<K: StatePartKind> StatePart<K> {
-    pub(crate) fn new(len: StatePartLen<K>) -> Self {
+    pub(crate) fn new(layout_data: &[K::LayoutData]) -> Self {
         Self {
-            value: K::new_state(len),
+            value: K::new_state(layout_data),
         }
     }
     pub(crate) fn borrow<'a>(&'a mut self) -> BorrowedStatePart<'a, K> {
@@ -2020,7 +2070,8 @@ impl From<Insns<InsnsBuilding>> for Insns<InsnsBuildingDone> {
                                 .address
                                 .expect("label address not set");
                         }
-                        InsnFieldType::SmallSlot(_)
+                        InsnFieldType::Memory(_)
+                        | InsnFieldType::SmallSlot(_)
                         | InsnFieldType::BigSlot(_)
                         | InsnFieldType::SmallSlotArrayIndexed(_)
                         | InsnFieldType::BigSlotArrayIndexed(_)
@@ -2032,7 +2083,10 @@ impl From<Insns<InsnsBuilding>> for Insns<InsnsBuildingDone> {
                             unreachable!()
                         }
                     },
-                    InsnFieldKind::Input | InsnFieldKind::Output | InsnFieldKind::Immediate => {}
+                    InsnFieldKind::Input
+                    | InsnFieldKind::Memory
+                    | InsnFieldKind::Output
+                    | InsnFieldKind::Immediate => {}
                 }
             }
         }
@@ -2050,6 +2104,7 @@ impl State {
         let Self {
             insns: _,
             pc,
+            memories: _,
             small_slots: _,
             big_slots: _,
         } = self;
@@ -2161,6 +2216,44 @@ fn cast_bigint_to_uint(src: &BigInt, dest_width: usize) -> BigInt {
     src & &*bigint_mask(dest_width)
 }
 
+fn memory_get_mut(
+    memory: &mut BitSlice,
+    addr: SmallUInt,
+    stride: usize,
+    start: usize,
+    width: usize,
+) -> Option<&mut BitSlice> {
+    let start = usize::try_from(addr)
+        .ok()?
+        .checked_mul(stride)?
+        .checked_add(start)?;
+    memory.get_mut(start..start.checked_add(width)?)
+}
+
+fn memory_read_big<T: BoolOrIntType>(
+    memory: &mut BitSlice,
+    addr: SmallUInt,
+    stride: usize,
+    start: usize,
+    width: usize,
+) -> Option<BigInt> {
+    let bits = memory_get_mut(memory, addr, stride, start, width)?;
+    Some(T::bits_to_bigint(bits))
+}
+
+fn memory_write_big<T: BoolOrIntType>(
+    memory: &mut BitSlice,
+    addr: SmallUInt,
+    stride: usize,
+    start: usize,
+    width: usize,
+    value: &BigInt,
+) -> Option<()> {
+    let bits = memory_get_mut(memory, addr, stride, start, width)?;
+    T::copy_bits_from_bigint_wrapping(value, bits);
+    Some(())
+}
+
 impl_insns! {
     #[insn = Insn, next_macro = next, branch_macro = branch]
     pub(crate) fn State::run(&mut self) -> () {
@@ -2702,6 +2795,78 @@ impl_insns! {
             next!();
         }
     }
+    MemoryReadUInt {
+        #[kind = Output]
+        dest: StatePartIndex<StatePartKindBigSlots>,
+        #[kind = Memory]
+        memory: StatePartIndex<StatePartKindMemories>,
+        #[kind = Input]
+        addr: StatePartIndex<StatePartKindSmallSlots>,
+        #[kind = Immediate]
+        stride: usize,
+        #[kind = Immediate]
+        start: usize,
+        #[kind = Immediate]
+        width: usize,
+    } => {
+        let addr = state.small_slots[addr];
+        state.big_slots[dest] = memory_read_big::<UInt>(&mut state.memories[memory], addr, stride, start, width).unwrap_or_default();
+        next!();
+    }
+    MemoryReadSInt {
+        #[kind = Output]
+        dest: StatePartIndex<StatePartKindBigSlots>,
+        #[kind = Memory]
+        memory: StatePartIndex<StatePartKindMemories>,
+        #[kind = Input]
+        addr: StatePartIndex<StatePartKindSmallSlots>,
+        #[kind = Immediate]
+        stride: usize,
+        #[kind = Immediate]
+        start: usize,
+        #[kind = Immediate]
+        width: usize,
+    } => {
+        let addr = state.small_slots[addr];
+        state.big_slots[dest] = memory_read_big::<SInt>(&mut state.memories[memory], addr, stride, start, width).unwrap_or_default();
+        next!();
+    }
+    MemoryWriteUInt {
+        #[kind = Input]
+        value: StatePartIndex<StatePartKindBigSlots>,
+        #[kind = Memory]
+        memory: StatePartIndex<StatePartKindMemories>,
+        #[kind = Input]
+        addr: StatePartIndex<StatePartKindSmallSlots>,
+        #[kind = Immediate]
+        stride: usize,
+        #[kind = Immediate]
+        start: usize,
+        #[kind = Immediate]
+        width: usize,
+    } => {
+        let addr = state.small_slots[addr];
+        memory_write_big::<UInt>(&mut state.memories[memory], addr, stride, start, width, &mut state.big_slots[value]);
+        next!();
+    }
+    MemoryWriteSInt {
+        #[kind = Input]
+        value: StatePartIndex<StatePartKindBigSlots>,
+        #[kind = Memory]
+        memory: StatePartIndex<StatePartKindMemories>,
+        #[kind = Input]
+        addr: StatePartIndex<StatePartKindSmallSlots>,
+        #[kind = Immediate]
+        stride: usize,
+        #[kind = Immediate]
+        start: usize,
+        #[kind = Immediate]
+        width: usize,
+    } => {
+        let addr = state.small_slots[addr];
+        memory_write_big::<SInt>(&mut state.memories[memory], addr, stride, start, width, &mut state.big_slots[value]);
+        next!();
+    }
     Return => {
         break;
     }
diff --git a/crates/fayalite/tests/sim/expected/connect_const.txt b/crates/fayalite/tests/sim/expected/connect_const.txt
index 189056b..f361cc3 100644
--- a/crates/fayalite/tests/sim/expected/connect_const.txt
+++ b/crates/fayalite/tests/sim/expected/connect_const.txt
@@ -23,6 +23,12 @@ Simulation {
                         ..
                     },
                 },
+                memories: StatePartAllocationLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
             },
             insns: [
                 // at: module-XXXXXXXXXX.rs:1:1
@@ -41,6 +47,9 @@ Simulation {
             ..
         },
         pc: 2,
+        memories: StatePart {
+            value: [],
+        },
         small_slots: StatePart {
             value: [],
         },
diff --git a/crates/fayalite/tests/sim/expected/connect_const_reset.txt b/crates/fayalite/tests/sim/expected/connect_const_reset.txt
index 5e6f0eb..0b0c043 100644
--- a/crates/fayalite/tests/sim/expected/connect_const_reset.txt
+++ b/crates/fayalite/tests/sim/expected/connect_const_reset.txt
@@ -35,6 +35,12 @@ Simulation {
                         ..
                     },
                 },
+                memories: StatePartAllocationLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
             },
             insns: [
                 // at: module-XXXXXXXXXX.rs:1:1
@@ -67,6 +73,9 @@ Simulation {
             ..
         },
         pc: 5,
+        memories: StatePart {
+            value: [],
+        },
         small_slots: StatePart {
             value: [],
         },
diff --git a/crates/fayalite/tests/sim/expected/counter_async.txt b/crates/fayalite/tests/sim/expected/counter_async.txt
index b72ebbb..0f49e80 100644
--- a/crates/fayalite/tests/sim/expected/counter_async.txt
+++ b/crates/fayalite/tests/sim/expected/counter_async.txt
@@ -72,6 +72,12 @@ Simulation {
                         ..
                     },
                 },
+                memories: StatePartAllocationLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
             },
             insns: [
                 // at: module-XXXXXXXXXX.rs:1:1
@@ -162,6 +168,9 @@ Simulation {
             ..
         },
         pc: 18,
+        memories: StatePart {
+            value: [],
+        },
         small_slots: StatePart {
             value: [
                 18446744073709551614,
diff --git a/crates/fayalite/tests/sim/expected/counter_sync.txt b/crates/fayalite/tests/sim/expected/counter_sync.txt
index dbb6134..30b84b2 100644
--- a/crates/fayalite/tests/sim/expected/counter_sync.txt
+++ b/crates/fayalite/tests/sim/expected/counter_sync.txt
@@ -68,6 +68,12 @@ Simulation {
                         ..
                     },
                 },
+                memories: StatePartAllocationLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
             },
             insns: [
                 // at: module-XXXXXXXXXX.rs:6:1
@@ -144,6 +150,9 @@ Simulation {
             ..
         },
         pc: 15,
+        memories: StatePart {
+            value: [],
+        },
         small_slots: StatePart {
             value: [
                 18446744073709551614,
diff --git a/crates/fayalite/tests/sim/expected/mod1.txt b/crates/fayalite/tests/sim/expected/mod1.txt
index 74ba140..cf15b07 100644
--- a/crates/fayalite/tests/sim/expected/mod1.txt
+++ b/crates/fayalite/tests/sim/expected/mod1.txt
@@ -83,6 +83,12 @@ Simulation {
                         ..
                     },
                 },
+                memories: StatePartAllocationLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
             },
             insns: [
                 // at: module-XXXXXXXXXX.rs:4:1
@@ -174,6 +180,9 @@ Simulation {
             ..
         },
         pc: 17,
+        memories: StatePart {
+            value: [],
+        },
         small_slots: StatePart {
             value: [],
         },
diff --git a/crates/fayalite/tests/sim/expected/shift_register.txt b/crates/fayalite/tests/sim/expected/shift_register.txt
index 5447d49..e89351d 100644
--- a/crates/fayalite/tests/sim/expected/shift_register.txt
+++ b/crates/fayalite/tests/sim/expected/shift_register.txt
@@ -84,6 +84,12 @@ Simulation {
                         ..
                     },
                 },
+                memories: StatePartAllocationLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
             },
             insns: [
                 // at: module-XXXXXXXXXX.rs:13:1
@@ -221,6 +227,9 @@ Simulation {
             ..
         },
         pc: 30,
+        memories: StatePart {
+            value: [],
+        },
         small_slots: StatePart {
             value: [
                 18446744073709551614,