diff --git a/erlang/apps/lib/src/extint.erl b/erlang/apps/lib/src/extint.erl
index d73eade..e885cdf 100644
--- a/erlang/apps/lib/src/extint.erl
+++ b/erlang/apps/lib/src/extint.erl
@@ -1,6 +1,11 @@
 %%% -*- erlang-indent-level: 2 -*-
 %%%
-%%% converts between 18 and 36-bit integers and sequences of nonets
+%%% Converts between fixed-width integers and sequences of bytes.
+%%% 16/32/64-bit integers are sequences of octets, while
+%%% 18/36-bit integers are sequences of nonets.
+%%%
+%%% For now, all conversions are big-endian.
+%%%
 %%% Copyright (C) 2013-2025  Mikael Pettersson
 %%%
 %%% This file is part of pdp10-tools.
@@ -20,24 +25,56 @@
 
 -module(extint).
 
--export([ uint18_to_ext/1
+-export([ uint16_from_ext/1
+        , uint16_to_ext/1
         , uint18_from_ext/1
-        , uint36_to_ext/1
+        , uint18_to_ext/1
+        , uint32_from_ext/1
+        , uint32_to_ext/1
         , uint36_from_ext/1
+        , uint36_to_ext/1
+        , uint64_from_ext/1
+        , uint64_to_ext/1
         ]).
 
 -include_lib("lib/include/stdint.hrl").
 
-%% The PDP10 is big-endian, so the conversions here are big-endian.
-%% The bytes (nonets) are numbered in storage order.
+-spec uint16_from_ext([uint8_t()]) -> uint16_t().
+uint16_from_ext([B0, B1]) ->
+  ((B0 band ?UINT8_MAX) bsl 8) bor (B1 band ?UINT8_MAX).
+
+-spec uint16_to_ext(uint16_t()) -> [uint8_t()].
+uint16_to_ext(U16) ->
+  [_B0 = (U16 bsr 8) band ?UINT8_MAX, _B1 = U16 band ?UINT8_MAX].
+
+-spec uint18_from_ext([uint9_t()]) -> uint18_t().
+uint18_from_ext([B0, B1]) ->
+  ((B0 band ?UINT9_MAX) bsl 9) bor (B1 band ?UINT9_MAX).
 
 -spec uint18_to_ext(uint18_t()) -> [uint9_t()].
 uint18_to_ext(U18) ->
   [_B0 = (U18 bsr 9) band ?UINT9_MAX, _B1 = U18 band ?UINT9_MAX].
 
--spec uint18_from_ext([uint9_t()]) -> uint18_t().
-uint18_from_ext([B0, B1]) ->
-  ((B0 band ?UINT9_MAX) bsl 9) bor (B1 band ?UINT9_MAX).
+-spec uint32_from_ext([uint8_t()]) -> uint32_t().
+uint32_from_ext([B0, B1, B2, B3]) ->
+  ((B0 band ?UINT8_MAX) bsl 24) bor
+  ((B1 band ?UINT8_MAX) bsl 16) bor
+  ((B2 band ?UINT8_MAX) bsl  8) bor
+   (B3 band ?UINT8_MAX).
+
+-spec uint32_to_ext(uint32_t()) -> [uint8_t()].
+uint32_to_ext(U32) ->
+  [_B0 = (U32 bsr 24) band ?UINT8_MAX,
+   _B1 = (U32 bsr 16) band ?UINT8_MAX,
+   _B2 = (U32 bsr  8) band ?UINT8_MAX,
+   _B3 =  U32         band ?UINT8_MAX].
+
+-spec uint36_from_ext([uint9_t()]) -> uint36_t().
+uint36_from_ext([B0, B1, B2, B3]) ->
+  ((B0 band ?UINT9_MAX) bsl 27) bor
+  ((B1 band ?UINT9_MAX) bsl 18) bor
+  ((B2 band ?UINT9_MAX) bsl  9) bor
+   (B3 band ?UINT9_MAX).
 
 -spec uint36_to_ext(uint36_t()) -> [uint9_t()].
 uint36_to_ext(U36) ->
@@ -46,9 +83,24 @@ uint36_to_ext(U36) ->
    _B2 = (U36 bsr  9) band ?UINT9_MAX,
    _B3 =  U36         band ?UINT9_MAX].
 
--spec uint36_from_ext([uint9_t()]) -> uint36_t().
-uint36_from_ext([B0, B1, B2, B3]) ->
-  ((B0 band ?UINT9_MAX) bsl 27) bor
-  ((B1 band ?UINT9_MAX) bsl 18) bor
-  ((B2 band ?UINT9_MAX) bsl  9) bor
-   (B3 band ?UINT9_MAX).
+-spec uint64_from_ext([uint8_t()]) -> uint64_t().
+uint64_from_ext([B0, B1, B2, B3, B4, B5, B6, B7]) ->
+  ((B0 band ?UINT8_MAX) bsl 56) bor
+  ((B1 band ?UINT8_MAX) bsl 48) bor
+  ((B2 band ?UINT8_MAX) bsl 40) bor
+  ((B3 band ?UINT8_MAX) bsl 32) bor
+  ((B4 band ?UINT8_MAX) bsl 24) bor
+  ((B5 band ?UINT8_MAX) bsl 16) bor
+  ((B6 band ?UINT8_MAX) bsl  8) bor
+   (B7 band ?UINT8_MAX).
+
+-spec uint64_to_ext(uint64_t()) -> [uint8_t()].
+uint64_to_ext(U64) ->
+  [_B0 = (U64 bsr 56) band ?UINT8_MAX,
+   _B1 = (U64 bsr 48) band ?UINT8_MAX,
+   _B2 = (U64 bsr 40) band ?UINT8_MAX,
+   _B3 = (U64 bsr 32) band ?UINT8_MAX,
+   _B4 = (U64 bsr 24) band ?UINT8_MAX,
+   _B5 = (U64 bsr 16) band ?UINT8_MAX,
+   _B6 = (U64 bsr  8) band ?UINT8_MAX,
+   _B7 =  U64         band ?UINT8_MAX].
diff --git a/erlang/rebar.config b/erlang/rebar.config
index b3d5d79..2c873ee 100644
--- a/erlang/rebar.config
+++ b/erlang/rebar.config
@@ -72,6 +72,12 @@
     %% only called from tests
   , {sim_core, run, 2}
     %% actual unused exports
+  , {extint, uint16_from_ext, 1}
+  , {extint, uint16_to_ext, 1}
+  , {extint, uint32_from_ext, 1}
+  , {extint, uint32_to_ext, 1}
+  , {extint, uint64_from_ext, 1}
+  , {extint, uint64_to_ext, 1}
   , {libelf, read_PhTab, 4}
   , {pdp10_opcodes, cpu_device_from_name, 2}
   , {pdp10_opcodes, models_from_name, 1}