# CollapseOS **URL:** \ **Category:** Programming\ **Tags:** ai\ **Created:** [October 21, 2026, 6:04am UTC](https://forum.cpcwiki.eu/t/collapseos/941 "2026-10-21T06:04:51Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![WacKEDmaN](https://forum.cpcwiki.eu/user_avatar/forum.cpcwiki.eu/wackedman/32/99_2.png) [@WacKEDmaN](https://forum.cpcwiki.eu/u/WacKEDmaN)\ **Post date:** [October 21, 2026, 6:04am UTC](https://forum.cpcwiki.eu/t/collapseos/941/1 "2026-10-21T06:04:51Z")
today i got claude to port [CollapseOS](https://collapseos.org/)to CPC and both DSK and M4 Board versions… its 100% text based and has got built in assembly and Forth compilers and editors… the version still uses CPCs firmware ![image](https://forum.cpcwiki.eu/uploads/default/original/2X/6/6ffc34babcc31bc8e1c08149abe3ffeae38e5c2c.png) [COLLAPS.ZIP](https://forum.cpcwiki.eu/uploads/short-url/7Wn07JGnRt2ahXu9pUbCs4Laczf.ZIP) (66.2 KB) [COLLAPS.DSK](https://forum.cpcwiki.eu/uploads/short-url/pNgOtDdqAYGikPJ5KTOplGBveBm.DSK) (190.3 KB) > **[GitHub - WacKEDmaN/CollapseOS-CPC](https://github.com/WacKEDmaN/CollapseOS-CPC)** > > Contribute to WacKEDmaN/CollapseOS-CPC development by creating an account on GitHub. * * * # Amstrad CPC Collapse OS (release 2021-04-21, Forth) on the Amstrad CPC 464 (with DDI-1), 664 and 6128. It boots from floppy (AMSDOS) or from an M4 board’s SD card, and keeps its blocks in ordinary AMSDOS files, so the same code works on both. ## Files All names the CPC sees are 8.3 or shorter (AMSDOS and the M4 board only handle 8.3 names, folders included). The program is called `COLLAPS`. `make` produces: - `os.bin`: the raw kernel, built to run at 0x0400. - `COLLAPS.BIN`: the same with an AMSDOS header. - `COLLAPS.BAS`: BASIC loader (ASCII). It POKEs a 41-byte boot stub (`boot.fs`) at 0x9000 and CALLs it. The stub loads `COLLAPS.BIN` to 0x0400 with CAS IN OPEN/DIRECT and jumps to it. - `blkgroups/Bnnn.BLK`: the blkfs split into 8K AMSDOS files. `B208.BLK` holds blocks 208-215. Empty groups are not written. - `COLLAPS.DSK`: 40-track AMSDOS DATA disc, Extended DSK container. Holds the loader, the kernel and the groups useful on a CPC: 0-23 (assemblers), 96-119 (block editor, VE), 200-239 (xcomp, core), 280-303 (Z80 kernel source) and 368-375 (CPC drivers). About 35K is left free. - `COLLAPS.ZIP`: everything for an M4 SD card, at the root of the zip: loader, kernel and all non-empty groups. ## Running Floppy (or Gotek/HxC with `COLLAPS.DSK`): ```auto RUN"COLLAPS ``` M4: unzip `COLLAPS.ZIP` into a folder with a name of 8 characters or less (e.g. `COLLAPS`) on the SD card, then ```auto |CD,"COLLAPS" RUN"COLLAPS ``` Do not use `RUN"COLLAPS.BIN"`: running a binary from BASIC resets the firmware. The background ROMs (AMSDOS, M4) get disconnected and block I/O falls back to cassette (verified: “Press PLAY then any key:”). The loader uses LOAD-style calls that keep them alive. The loader refuses to start if HIMEM is below &9FFF. That happens when other ROMs reserved too much memory, which would overlap Collapse OS’s stacks. ## First steps Collapse OS words take their arguments from the stack, before the word: ```auto 0 LIST list block 0 (the master index) LIST -> "stack underflow": LIST needs a block number 100 LIST block editor source 110 LOAD VE load and start the Visual Editor (q quits) 5 LOAD load the Z80 assembler 2 3 + . prints 5 ``` ## Design: firmware stays resident Like the TRS-80 recipe, this port uses the machine’s own firmware for I/O. It never touches the interrupt mode or vector. - `(emit)` → TXT OUTPUT (0xbb5a), screen mode 2 (80x25). - `(key?)` → KM READ CHAR (0xbb09). Characters \>= 0x80 (cursor keys, COPY, …) are ignored. ESC’s break mechanism is disarmed. - `AT-XY` → TXT SET CURSOR (0xbb75). `COLS` `LINES` `CELL!` `XYMODE` make the Visual Editor work (`110 LOAD` then `VE`). - `BYE` resets the machine. Extra words: - `FW ( af bc de hl addr -- af bc de hl )` calls any firmware routine. A is the MSB of `af`, carry is bit 0 of the returned `af`. Example: `0x0700 0 0 0 0xbb5a FW 2DROP 2DROP` beeps. - `FW0 ( addr -- )` calls a routine without arguments. - `MODE ( n -- )` sets screen mode (COLS stays 80; VE wants mode 2). - `CMOVE ( src dst u -- )` copies memory with LDIR. ### The shadow-register rule The CPC firmware interrupt handler (`0x0038: jp 0xb941`) starts with `di / ex af,af' / jr c,... / exx / ... out (c),c`. It keeps its re-entrancy flag in AF’ and the Gate Array port in BC’. Code that runs `EXX` or `EX AF,AF'` while interrupts are enabled crashes the machine at the next interrupt. The Z80 kernel uses `EXX,` (FIND, `*`, `/MOD`, `[]=`, CRC16) and `EXAFAF',` (CARRY? and `+` `-` `*`). Block 370, loaded between the assembler and B280, redefines those two assembler words. `EXX,` swaps DE with a RAM slot, and `EXAFAF',` swaps AF with a RAM slot. The kernel only ever uses EXX to protect DE (IP) and EX AF,AF’ to stash the carry, so the behaviour is identical. The upstream blocks are unchanged. If you assemble your own code on the CPC (`5 LOAD`), do not use `EXX,` or `EXAFAF',` unless you first load the same redefinitions: `0x9ba0 CONSTANT DRVMEM 370 LOAD`. ### Blocks: AMSDOS group files AMSDOS has no random access, so blocks are grouped by 8 into 8K files, read and written whole with CAS IN/OUT DIRECT. Two groups are cached in RAM with LRU, so nested `LOAD`s that jump between a parent block and its children don’t re-read the disc. Writing a block rewrites its group file (write-through). AMSDOS then renames the old file to `.BAK`, so the driver erases that `.BAK` with `|ERA` right away (KL FIND COMMAND + KL FAR PCHL). Otherwise every edited group would leave 9K behind and the disc would fill up. A block in a group with no file reads as empty. AMSDOS prints `Bnnn.BLK not found` when that happens: it always prints this message, with no flag to disable it (checked in the AMSDOS ROM: `CEC4 jp nc,D50C -> ld a,6 -> print`). The first write creates the file. Group files carry an AMSDOS header. Headerless files can’t be read with CAS IN DIRECT (tested), so each 8K group takes 9K on disc. ## Memory map ```auto 0x0000-0x03ff firmware restarts, BASIC (unused once we run) 0x0400 kernel (~7K), then BLK( buffer and the dictionary 0x5300-0x5aff CASBUF, AMSDOS 2K buffer 0x5b00-0x9aff GRPBUF, two 8K group slots 0x9b00-0x9bff SYSVARS, DRVMEM 0x9c00 RS (grows up) 0x9ffe PS (grows down) 0xa000- firmware, AMSDOS, M4 workspace ``` The dictionary has about 12K: the Z80 assembler uses ~2.9K, the editors ~2.5K. Buffers passed to the firmware and the stacks must be inside 0x4000-0xbfff. While the firmware runs (its interrupts included), it pages ROM over the rest. ## Speed Loading source is CPU bound: Collapse OS looks up every word with a linear dictionary search. On a CPC a block takes 1-2 seconds, so `110 LOAD` (VE) takes about 70 seconds and `5 LOAD` (assembler) about a minute (measured in MAME). Reading or writing a group takes a few seconds on a floppy. While AMSDOS transfers sectors, interrupts are off and the firmware doesn’t scan the keyboard, so keys pressed during disc activity can be missed. ## Verified in MAME 0.264 (cpc6128 and cpc464 + DDI-1) - Boot from the DSK with `RUN"COLLAPS`, banner, interpreter. - `LIST` from group files, a missing group reads as empty. - `COPY` writes blocks: new group files are created, existing ones rewritten. Reading back after cache eviction is correct, and no `.BAK` is left behind (checked with CAT). - `110 LOAD` + `VE`: Visual Editor draws and edits, `q` exits. - `5 LOAD`, `LIVETGT`, a CODE word assembled and run on the CPC (`3 X7 .` → 10), and `FW` calling TXT OUTPUT. - VE edit cycle: type into an empty block, `q`, `FLUSH`, evict the cache, `LIST` shows the text read back from disc. - On the 464 + DDI-1: boot, `LIST`, `COPY`. The M4 board can’t be emulated here. It patches the same AMSDOS/CAS vectors this port uses, but that part has not been tested on M4 hardware. ---
**Author:** ![Rambo](https://forum.cpcwiki.eu/user_avatar/forum.cpcwiki.eu/rambo/32/1251_2.png) [@Rambo](https://forum.cpcwiki.eu/u/Rambo)\ **Post date:** [October 21, 2026, 8:37pm UTC](https://forum.cpcwiki.eu/t/collapseos/941/2 "2026-10-21T20:37:29Z")
Probably a really silly question, but what is it used for? ---
**Author:** ![WacKEDmaN](https://forum.cpcwiki.eu/user_avatar/forum.cpcwiki.eu/wackedman/32/99_2.png) [@WacKEDmaN](https://forum.cpcwiki.eu/u/WacKEDmaN)\ **Post date:** [October 22, 2026, 1:48am UTC](https://forum.cpcwiki.eu/t/collapseos/941/3 "2026-10-22T01:48:45Z")
its a complete cross development environment… "[Winter is coming](https://collapseos.org/why.html) and Collapse OS aims to soften the blow. It is a Forth [(why Forth?)](https://collapseos.org/forth.html) operating system and a collection of tools and documentation with a single purpose: preserve the ability to program microcontrollers through [civilizational collapse](https://collapseos.org/civ.html). It is designed to: 1. Run on minimal and improvised machines. 2. Interface through improvised means (serial, keyboard, display). 3. Edit text and binary contents. 4. Compile assembler source for a wide range of MCUs and CPUs. 5. Read and write from a wide range of storage devices. 6. Assemble itself and deploy to another machine." is mainly meant for building a system from scrap parts after a civilization crash…but it can still be used today, it has compilers, drivers and tools for z80, 6809 and 8086 cpus, and AVR based mcus ---
**Author:** ![Rambo](https://forum.cpcwiki.eu/user_avatar/forum.cpcwiki.eu/rambo/32/1251_2.png) [@Rambo](https://forum.cpcwiki.eu/u/Rambo)\ **Post date:** [October 22, 2026, 7:10am UTC](https://forum.cpcwiki.eu/t/collapseos/941/4 "2026-10-22T07:10:57Z")
ok thanks for the reply