MiSTer Computer Cores

July 23, 2026 · View on GitHub

This document cross-references every computer core listed on the MiSTer wiki (https://mister-devel.github.io/MkDocs_MiSTer/cores/computer/) against the filesystems Rusty Backup currently implements, and estimates the work to support the disk types (floppy / hard disk / CD-ROM) of the outstanding cores.

What Rusty Backup supports today

Filesystems: FAT12/16/32, exFAT, NTFS, HPFS (OS/2; read + edit + create + fsck), HFS, HFS+/HFSX, APFS (read-only browse + extract, incl. FileVault via password / recovery key; no snapshots), ext2/3/4, XFS, SquashFS v4.0 (read + edit — the read-only root filesystem of Buildroot and other appliance images, and of casper/filesystem.squashfs inside live-CD ISOs. Compressors read: gzip [fixture-tested] / XZ / LZMA / LZ4 / zstd; write: gzip / XZ / zstd. The format has no in-place write, so create / delete / mkdir / rename / symlink commit by rebuilding the whole image the way mksquashfs does — unchanged files keep their exact bytes, permissions, ownership, timestamps and xattrs. No fsck: SquashFS carries no checksums, so there is nothing to repair from), JFS, ReiserFS, UFS1/UFS2, btrfs, Minix V1/V2/V3 (read + edit + create + fsck), ProDOS (read + edit + create + fsck), Apple DOS 3.3 (read + edit + create + fsck), UCSD p-System (read + edit + create + fsck), MacPlus MFS (read + edit + create + fsck), Amiga OFS/FFS (AFFS) / PFS3 / SFS, IRIX EFS, CP/M (read + edit + create + fsck; multi-DPB: amstrad_data / amstrad_sys / amstrad_pcw / einstein / svi328_cpm / altair_8in / altair_cf / multicomp / zxplus3), Human68k, ADFS (read + edit [new-map + old-map D] + E-format create + new-map fsck), QDOS (QXL.WIN read + write + resize), QDOS Microdrive (detect-only scaffold), CBM DOS (1541 / 1571 / 1581 + PET 8050 / 8250 IEEE-488 read + write + fsck; add/delete bidirectionally cross-validated against the c1541 / Python d64 reference, fsck = VALIDATE with the BAM rewrite byte-verified against c1541 validate), Atari DOS 2 (2.0S / 2.5 read + write + create + fsck, .atr / .xfd), RS-DOS / CoCo Disk BASIC (read + write + fsck, raw 35- / 40-track .dsk / .jvc; cross-validated against an independent clean-room reader/writer derived from the toolshed libdecb semantics; fsck = granule-table reconciliation vs the directory chains, VALIDATE model), OS-9 / NitrOS-9 RBF (hierarchical Unix-like FS — read + write incl. subdirectories + create + fsck, raw .dsk / .vdk; cross-validated byte-exact against an independent clean-room RBF reader on real NitrOS-9 toolshed disks, fsck validated clean on the real fixture), DragonDOS (Dragon 32/64 read + write + fsck, single- / double-sided 40-track .dsk; cross-validated byte-exact against an independent clean-room reader/writer and against real third-party DragonDOS disks; fsck = sector-bitmap reconciliation, VALIDATE model), Acorn DFS (BBC Micro / BBC Master / Acorn Electron read + write + fsck, single-sided .ssd 40-/80-track and double-sided .dsd — the two track-interleaved sides de-interleave into two Acorn DFS partitions (@1 / @2), edits re-interleaving on save; flat catalogue in sectors 0–1, contiguous files in descending start-sector order, single-character directory namespaces; bidirectionally cross-validated byte-exact against an independent clean-room DFS reader/writer; fsck = contiguous-file consistency + canonical-order repair), TR-DOS (ZX Spectrum Beta Disk read + write + create + fsck, raw .trd 80-/40-track single-/double-sided; a flat 128-entry catalogue of contiguous files packed from a first-free high-water mark; every write cross-validated against an independent clean-room oracle, fsck = catalogue-packing + disk-info-counter reconciliation), TI-99/4A (read + write + create + fsck, flat V9T9 .dsk SSSD/DSSD/DSDD; a VIB allocation bitmap + a sorted FDIR of extent-based File Descriptor Records, big-endian; every write cross-validated against BOTH MAME's imgtool reader and an independent clean-room oracle, fsck = bitmap-vs-directory-walk reconciliation), Oric Jasmin (read + edit + create + fsck, flat 256-byte-sector .dsk SS 178 KB / DS 356 KB; free map + chained directory + sector-list inodes; modeled on MAME's fs_oric_jasmin and cross-validated against floptool), ANDOS (detect-only scaffold), and the optical-disc filesystems (ISO 9660
- Joliet / Rock Ridge, High Sierra, UDF, HFS, HFS+, SGI EFS, UFS/FFS, VMS ODS-2, plus the video-game console filesystems Nintendo GameCube / Wii, Philips CD-i, and 3DO Opera — browse/extract, see Optical / CD-ROM below).
Partition tables: MBR, GPT, APM, Amiga RDB, Atari AHDI, Sharp X68000.
Containers: CHD, VHD (fixed + dynamic), QCOW2, VMDK, 2MG, WOZ, DC42, HFV, IMZ (encrypted ZIP), .zip (a RAW disk image inside a plain ZIP, inflated sparsely; --inside picks among multiple), GHO/GHS (Ghost SECTOR mode), MSA (Atari ST), EDSK/DSK (Amstrad CPC / PCW / Einstein / etc.), .d88 (Sharp X68000 / PC-88 / PC-98 / MSX / FM-7), Acorn .hdf (bare + Arculator-wrapped), Apple-II .do / .po / .dsk sector-order, gzip-wrapped Amiga .adz / .hdz.
Raw / superfloppy (partitionless) images are handled.
Optical / CD-ROM: rip a physical CD/DVD drive to ISO or BIN/CUE (optical rip), list drives (optical drives), convert ISO <-> BIN/CUE <-> CD-CHD (optical convert), and browse/extract ISO 9660 (+ Joliet / Rock Ridge), High Sierra, UDF, HFS, HFS+, SGI EFS, UFS/FFS, VMS ODS-2, and the video-game console discs — Nintendo GameCube / Wii (Wii decrypted internally, no key needed), Sega Dreamcast GD-ROM (.gdi + CHD), Philips CD-i, and 3DO — disc images, with console / serial / title / region identification. Built into both the desktop release and the MiSTer rb-cli-mini armv7 build (via opticaldiscs 0.8.0), for devices with an attached drive (e.g. the SuperStation One).
Remote optical ripping: the desktop app / CLI can drive a remote daemon's optical drive over the rb-daemon — the device (e.g. a MiSTer) only issues SCSI reads while the desktop does all the encoding (CHD compression never taxes the armv7 CPU). optical drives --remote host:port to discover; optical rip --device rb://host:port/dev/sr0, or the GUI Optical tab's "Add remote daemon..." button. See docs/remote_ripping.md.

Legend for the Support column:

Yes — filesystem + media path already work end to end.
Partial — one media path or one filesystem is covered, others are not.
No — outstanding; needs new filesystem (and sometimes container/partition) work.
N/A — tape / cartridge / ROM-only core; no disk filesystem to support.

Unified support table (all 64 cores)

Core	System	Media	Filesystem(s)	Rusty Backup support
ao486	486DX33 PC	Floppy, HDD, CD	FAT12 / FAT16/32 (MBR) / HPFS (OS/2) / ISO9660	Yes
PCXT	IBM PC/XT	Floppy, HDD	FAT12 / FAT12-16 (MBR)	Yes
MSX	MSX/MSX2/TurboR	Floppy, HDD	FAT12 / FAT16 (Nextor VHD)	Yes
MSX1	Microsoft MSX1	Floppy, HDD	FAT12 / FAT12-16	Yes
ZXNext	ZX Spectrum Next	SD/HDD (VHD)	FAT32/16/12	Yes
TSConf	ZX-Evolution	SD/HDD (VHD)	FAT32 (non-MBR)	Yes
Minimig-AGA	Commodore Amiga	Floppy, HDD, CD	OFS/FFS, PFS3, SFS (RDB) / ISO9660	Yes
MacPlus	Macintosh Plus	Floppy, HDD	HFS / MFS (400K floppy)	Yes — HFS + MFS both read/edit/create/fsck (400K / 800K MFS floppy)
AtariST	Atari ST/STe	Floppy, HDD	GEMDOS = FAT12 / FAT16	Partial — FAT yes; needs Atari AHDI partition table for HDD
Apple-II	Apple IIe	Floppy, HDD	DOS 3.3 / ProDOS	Yes — ProDOS (read + edit + create + fsck; `rb-cli new volume prodos`) + Apple DOS 3.3 (read + edit + create + fsck; `rb-cli new floppy apple-dos`, 140 KB `.dsk`/`.do`/`.po`). Sector-order auto-detect via `containers::sector_order`.
ZX-Spectrum	Sinclair ZX Spectrum	Floppy, SD/HDD	TR-DOS, G+DOS, +3DOS (CP/M-like), esxDOS FAT	Partial — TR-DOS (`.trd`, full quartet) + esxDOS FAT yes; +3DOS via CP/M (`zxplus3` preset); G+DOS (MGT) no
X68000	Sharp X68000	Floppy, SASI/SCSI HDD	Human68k (FAT-derived dialect)	Yes — floppy (Human68k read/browse/extract + add/delete/mkdir on `.d88` / `.xdf` / `.hdm` / `.dim`; edits decode->mutate->re-encode back into the container, GUI and CLI) and SASI/SCSI HDD (`.hda` / `.hdf` / `.hds`) read/browse/extract/add/delete/mkdir + in-place FS grow/shrink (`rb-cli resize`) + defragmenting repack (`rb-cli repack` / Inspect-tab "Defragment…" — packs files contiguously, reclaiming holes left by deletions) + fsck (`rb-cli fsck` / Inspect-tab Check — FAT-chain reconciliation + FAT-mirror resync, lost-cluster reclaim), incl. real BlueSCSI `X68SCSI1` 1024-byte-sector images (sector size derived from the boot signature; Sharp/KG big-endian BPB + big-endian FAT). Verified byte-exact on the BlueSCSI HD10 SCSI fixture and the Populous/Lemmings/SSF2/Votoms 256-byte SASI game disks across grow→shrink round-trips (multi-cluster `COMMAND.X` + Japanese filenames survive). Backup/restore/reconstruct honor the true (non-512-aligned) partition byte offset via the persisted `start_byte`, so SASI backup→restore lands the partition region byte-identical. New 2026-06-10: `rb-cli new hd x68k` scaffolds self-bootable SASI/SCSI HDDs from scratch — emits the Sharp IPL signature, X68K partition table, IPL stub (halt or printed-banner via IOCS B_PRINT), and optionally clones an entire Human68k donor floppy (flat or `.dim` / `.D88` / `.xdf` / `.hdm`) into the partition. MAME-verified on `x68000 -sasi` (SASI variant, 256-B sectors) and `x68030 -hard` (SCSI variant, 1024-B sectors). The donor's `SWITCH.X /HD` installs the partition boot sector on first FDD0 boot, after which the HDD self-boots to C:. Zero-manual-step mode also available: `--boot-sector-donor hd0.hds --size 100M --variant scsi` extracts the Sharp partition boot sector (Sharp IPL Copyright 1990 SHARP) from the well-known `hd0.hds` 100 MB Sharp/Keisoku Giken donor at build time and overlays it onto the output partition — no `SWITCH.X` step needed, self-boots straight to C:> on first power-on. Sharp's boot-sector bytes never live in the rusty-backup repo; same legal pattern as `--system-disk` (you provide the donor file, the bytes flow user→user).
Archie	Acorn Archimedes	Floppy, HDD	ADFS / FileCore	Yes (new-map) — full quartet on the new-map layouts (E / F / HD): read + browse, edit (create / delete / rename via the FSM allocator), create blank E-format floppies (`rb-cli new floppy adfs`, 800 KB single-zone new-map FSM), and fsck (zone-checksum + cross-check verify + allocated-fragment-vs-directory-tree reconciliation; repair re-stamps the zone checksums, leaked-fragment reclaim withheld pending a full `CheckMap`-style map rebuild). Disc Record scan spans the HD / E-format-floppy / legacy-floppy candidate offsets (0xFC0 / 0x404 / 0xDC0); byte-correct against marutan.net blank HD samples (`blank256E.hdf`, `blank1024Eplus.hdf`) and the 8bs.com `arc-04.800.adf` (E-format populated). Old-map D-format* (no Disc Record; old free-space map + Hugo root at byte 1024) now reads and writes too — detect + read + create/delete/rename validated against real Repton 3 / Lemmings floppies (writes keep the old-map checksums valid so RISC OS still mounts the disc). `.adf` 800K floppy + bare and Arculator-wrapped `.hdf` HDD containers all handled. (Double-sided DFS `.dsd` is now supported via the `fs::dfs` path — see the BBCMicro row. Still open: double-sided ADFS L-format `.adl`.)
QL	Sinclair QL	Microdrive, HDD	QDOS (QXL.WIN)	Partial — QXL.WIN HDD read + write end-to-end (byte-correct against kilgus + smsqe MiSTer samples; write path validated against headless sQLux oracle — rb-cli put → SuperBASIC COPY → host file round-trips byte-exact, per-file 64-byte QDOS header convention honoured); `.mdv` microdrive detect + cart-name surfaced (full directory walk parked at OPEN-WORK §7 behind real-hardware oracle)
Amstrad	Amstrad CPC 6128	Floppy	AMSDOS, CP/M 2.2/Plus	Yes — `fs::cpm` ships the `amstrad_data` + `amstrad_sys` DPBs covering both CPC data + system formats.
AmstradPCW	Amstrad PCW	Floppy	CP/M Plus	Yes — `fs::cpm` `amstrad_pcw` DPB.
TatungEinstein	Tatung Einstein	Floppy	Xtal/DOS (CP/M-compatible)	Yes — `fs::cpm` `einstein` DPB.
SVI328	Spectravideo SV-328	Floppy	CP/M (MSX-DOS/FAT12 possible)	Partial — CP/M side covered by `svi328_cpm` DPB; the MSX-DOS / FAT12 floppy variant routes through the existing FAT driver but no SV-specific BPB quirks have been validated.
Altair8800	MITS Altair 8800	Floppy, IDE/CF	CP/M	Yes — `fs::cpm` ships both `altair_8in` (8-inch floppy) and `altair_cf` (CompactFlash HDD) DPBs.
MultiComp	Grant Searle MultiComp	Floppy	CP/M	Yes — `fs::cpm` `multicomp` DPB.
C64	Commodore 64/128	Floppy	CBM DOS (flat track/sector)	Yes — `fs::cbm` reads + writes `.d64` (1541) / `.d71` (1571) / `.d81` (1581); add/delete cross-validated against `c1541` / Python `d64`.
C128	Commodore 128	Floppy	CBM DOS	Yes — `fs::cbm` `.d64` / `.d71` / `.d81`.
C16	Commodore C16/Plus4	Floppy	CBM DOS	Yes — `fs::cbm` `.d64` (1541).
VIC20	Commodore VIC-20	Floppy	CBM DOS	Yes — `fs::cbm` `.d64` (1541).
PET2001	Commodore PET	Floppy (IEEE-488)	CBM DOS (D80/D82)	Yes — `fs::cbm` reads + writes the 8050 `.d80` (533248 B, 77 trk) and 8250 `.d82` (1066496 B, 154 trk) geometries: 29/27/25/23 zone map, BAM on track 38 (2–4 chained sectors, 5-byte/track entries), directory on track 39. Bidirectionally cross-validated against the Python `d64` reference (read + write byte-exact). `.d64` (1541/2031/4040) also works.
BBCMicro	BBC Micro B/Master	Floppy	Acorn DFS / ADFS	Yes — `fs::dfs` reads + writes Acorn DFS single-sided `.ssd` (40-track 100K / 80-track 200K) and double-sided `.dsd` (the two track-interleaved sides de-interleave into two Acorn DFS partitions `@1` / `@2`, edits re-interleaving on save): flat catalogue in sectors 0–1, up to 31 contiguous files in descending start-sector order, single-character directory namespaces, 18-bit load/exec/length, lock bits. Read/browse/extract + add/delete bidirectionally cross-validated byte-exact against an independent clean-room DFS reader/writer (locked files, non-`$` dirs, real load/exec all round-trip); the `.dsd` de-interleave + `@1`/`@2` split validated against real BBC PD music discs. ADFS floppies (`.adf`) are handled by `fs::adfs` (see the Archie row).
AcornElectron	Acorn Electron	Floppy	DFS / ADFS	Yes — same `fs::dfs` Acorn DFS read + write as BBCMicro (single-sided `.ssd` + double-sided `.dsd`, the latter presented as two partitions). ADFS floppies handled by `fs::adfs`.
AcornAtom	Acorn Atom	Tape, Floppy	Atom DOS	No
CoCo2	Tandy CoCo 2	Floppy	RS-DOS / DragonDOS, OS-9 (RBF)	Yes — `fs::rsdos` reads + writes RS-DOS / Disk BASIC (granule allocation table on track 17, 72-file directory, granule-chain files; raw 35- / 40-track `.dsk` / `.jvc`), `fs::os9` reads + writes OS-9 / NitrOS-9 RBF (hierarchical FS; `.dsk` / `.vdk`, byte-exact cross-validated against a clean-room RBF reader on real toolshed disks), and `fs::dragondos` reads + writes DragonDOS (see Dragon row).
Dragon	Dragon 32/64	Floppy	DragonDOS, OS-9 (RBF)	Yes — `fs::dragondos` reads + writes DragonDOS (directory track 20 + backup track 16, one's-complement geometry signature, set-bit-free sector bitmap, 25-byte header/continuation directory entries; single- / double-sided 40-track `.dsk`). Byte-exact cross-validated against an independent clean-room reader/writer AND against real third-party DragonDOS disks (rolfmichelsen/dragontools' empty volume plus a populated 9-file AGD-suite disk, all files byte-identical across both readers). `fs::os9` covers OS-9 / NitrOS-9 RBF.
CoCo3	Tandy CoCo 3	Floppy/virtual	RS-DOS, OS-9 / NitrOS-9 (RBF)	Yes — `fs::rsdos` RS-DOS / Disk BASIC read + write (see CoCo2) and `fs::os9` OS-9 / NitrOS-9 RBF read + write (add/delete incl. subdirectories), the two filesystems the CoCo3 core uses.
TRS-80	Tandy TRS-80	Floppy (JV1)	TRSDOS / LDOS / NEWDOS	No
Atari800	Atari 8-bit	Floppy, ltd HDD	Atari DOS (DOS 2.x)	Yes — `fs::atari_dos` reads + writes + creates + fscks Atari DOS 2.0S/2.5 (VTOC@360 bit-set-free bitmap, 64-file directory @361-368, linked-sector files). Single + enhanced density `.atr` / `.xfd`; `rb-cli new floppy atari` formats a blank SD disk, and fsck reconciles the VTOC bitmap + free-count against the directory chains. Read validated byte-exact against a real DOS 2.0S system disk + an independent clean-room reader; write validated the same way; fsck validated clean on the real fixture.
TI-99_4A	TI-99/4A	Floppy	TI floppy FS (VIB/FDIR)	Yes — full quartet on the V9T9 `.dsk` (read + edit + create + fsck)
Oric	Tangerine Oric	Floppy	Jasmin (read+edit+create+fsck); Sedoric pending	Partial
SharpMZ	Sharp MZ	Floppy, Tape	Sharp MZ FD format	No
PC88	NEC PC-8801 mkII SR	Floppy	N88-BASIC Disk BASIC	No
SAM-Coupe	SAM Coupe	Floppy	SAM DOS / MasterDOS	No
ColecoAdam	Coleco Adam	Floppy, DDP tape	EOS (read-only in core)	No
BK0011M	Elektronika BK	Floppy, HDD (VHD)	ANDOS / CSIDOS	Partial — `fs::andos` ships a detect-only scaffold (boot-block signature probe surfaces "ANDOS" through `fs_type()`). Browse / extract returns `Unsupported`; CSIDOS not started. Sparse public docs limit the work to what real-disc fixtures can validate.
Vector-06C	Vector-06C	Floppy	MicroDOS	No
Specialist	Specialist	Floppy	Specialist-MX FS	No
ZX81	Sinclair ZX80/ZX81	Tape	—	N/A
Apple-I	Apple I	ROM/program	—	N/A
Aquarius	Mattel Aquarius	Cart, Tape	—	N/A
Apogee	Apogee BK-01	Tape/ROM	—	N/A
AliceMC10	Matra Alice	Tape	—	N/A
Casio_PV-2000	Casio PV-2000	Cartridge	—	N/A
Chip8	CHIP-8	Program/ROM	—	N/A
EDSAC	EDSAC	Paper tape	—	N/A
EG2000	EACA Colour Genie	Tape, Cart	—	N/A
Galaksija	Galaksija	Tape	—	N/A
Homelab	Compukit Homelab	Tape	—	N/A
Interact	Interact	Tape	—	N/A
Jupiter	Jupiter Ace	Tape, Cart	—	N/A
Laser310	Vtech Laser 310	Tape	—	N/A
Lynx48	Camputers Lynx	Tape	—	N/A
OndraSPO186	Tesla Ondra SPO-186	Tape	—	N/A
Orao	PEL Varazdin Orao	Tape	—	N/A
PDP1	DEC PDP-1	Paper tape	—	N/A
PMD85	Tesla PMD 85	ROM, Tape	—	N/A
RX-78	Bandai RX-78	Cartridge	—	N/A
SordM5	Sord M5	Cart, Tape	—	N/A
TomyTutor	Tomy Tutor	Cart, Tape	—	N/A
UK101	Compukit UK101	Tape/program	—	N/A

Tally: 7 fully supported, 4 partial, 30 outstanding (No), 23 N/A (tape/cart/ROM-only).

Outstanding work, grouped by filesystem

Estimates assume one developer fluent in the codebase, and cover detect + browse/inspect + backup compaction. Edit / fsck / resize is an additional increment, only worthwhile on HDD-capable cores. Effort: S ~= days, M ~= 1-3 weeks, L ~= 3-6 weeks.

Rusty Backup's differentiators (resize, compaction, CHD/VHD/zstd compression) only matter for hard-disk-capable cores. Most outstanding cores are floppy-only with tiny fixed-geometry disks (140 KB-800 KB) where there is nothing to resize or compact — the work there is browse / inspect / verify / convert only.

Highest value — hard-disk-capable (resize/compaction pays off)

Filesystem	Cores unlocked	Effort	Notes / extra support needed
CP/M (parameterized)	Amstrad, AmstradPCW, TatungEinstein, SVI328, Altair8800, MultiComp (+ ZX +3DOS)	M-L	One implementation with a per-machine diskdef/DPB registry (like cpmtools) covers ~6 cores. Biggest core-count payoff. Needs EDSK container decoder.
Human68k	X68000	M	FAT-derived — can reuse FAT scaffolding, but needs 18.3 names, Shift-JIS, case-sensitivity, X68k partition scheme. Needs .d88/.dim container decoder.
ADFS / FileCore	Archie (+ BBC/Electron ADFS)	M-L	Acorn-proprietary 256-byte-block FS with free-space map. Strip Arculator <=0.99 512-byte header.
QDOS	QL	M	QXL.WIN hard-disk container; resize valuable. Microdrive .mdv is fixed-size.

Medium value — mostly floppy-only (browse/inspect/convert, no resize)

Filesystem	Cores unlocked	Effort	Notes / extra support needed
CBM DOS	C64, C128, C16, VIC20, PET2001	M	Flat single-directory track/sector. Raw .d64/.d71/.d81/.d80/.d82 easy; needs GCR decoder for .g64/.g71 (+S-M). No resize concept.
Acorn DFS	BBCMicro, AcornElectron	S	Trivial flat catalogue in track 0. (ADFS shares FileCore work above.)
RS-DOS/DragonDOS + OS-9 RBF	CoCo2, CoCo3	M each	RS-DOS granule table (a "FAT" in name only). OS-9 RBF is a separate Unix-like FS. Needs .jvc/.vdk handling.
Atari DOS	Atari800	S-M	DOS 2.x family on .atr.
TI-99 FS	TI-99_4A	M	VIB + FDIR sector scheme on .dsk.
TRS-80 DOS	TRS-80	M	TRSDOS/LDOS/NEWDOS variants on JV1 sector dumps.
Sedoric (Oric DOS)	Oric	S-M	Jasmin DONE (`src/fs/oric.rs`); Sedoric still pending.
N88-BASIC	PC88	M	Needs .d88 container (shared with X68000).
Sharp MZ FD	SharpMZ	S-M	Per-machine floppy format.
EOS	ColecoAdam	S-M	Block-based, read-only in the core -> read/browse only.
Atom DOS	AcornAtom	S-M	Niche; mostly a tape machine.
SAM DOS / MasterDOS	SAM-Coupe	S-M	MGT 800K layout (shares family with Spectrum G+DOS).

Low value — niche Soviet / hobby cores

Filesystem	Cores	Effort	Notes
ANDOS / CSIDOS	BK0011M (has .vhd HDD)	M	Only outstanding Soviet core with HDD.
MicroDOS	Vector-06C	M	Needs .fdd/.edd container.
Specialist-MX FS	Specialist	M	Needs .odi container.

Near-complete touch-ups (small wins)

Item	Core(s)	Effort	Notes
Atari AHDI partition table	AtariST	S	Atari's MBR-like scheme; makes ST hard-disk images first-class (FAT already supported).
Apple DOS 3.3	Apple-II	S-M	Complements existing ProDOS; covers sector-order .dsk/.do.

CD-ROM summary

CD-ROM support is effectively done. Only ao486 (ISO9660) and Amiga CD32 (data CDFS = ISO9660; audio not implemented in the core) use CD media. No other computer core uses CD-ROM, so no new optical work is required.

(The optical browser reads far more than the cores need — UDF, High Sierra, HFS / HFS+, SGI EFS, UFS/FFS, VMS ODS-2, and the video-game console filesystems GameCube / Wii, CD-i, and 3DO Opera in addition to ISO 9660 — so no CD-using core is filesystem-blocked.)

Recommended sequencing (best coverage per unit effort)

CP/M (parameterized + EDSK decoder) — unlocks ~6 cores including two HDD-relevant ones. Biggest payoff.
CBM DOS (+ GCR) — unlocks 5 Commodore cores.
Near-complete touch-ups — AtariST AHDI partition table, Apple DOS 3.3.
Human68k, ADFS/FileCore, QDOS — the three outstanding HDD filesystems where resize/compaction actually pays off.
Everything else is floppy-only long-tail: implement on demand; browse/inspect-only is usually enough.

A recurring sub-task: several formats are container formats (.d88, EDSK, .g64/.g71, .msa, .dim, .vdk/.jvc, .fdd/.edd, .odi, .nib) that wrap sectors with per-track geometry. Build a shared "decode container -> flat LBA sectors" layer feeding the superfloppy path, reused across cores — budget that as one M infrastructure piece rather than re-solving it per filesystem.

Prior art: TotalImage and existing Rust crates

Survey done 2026-05-31 to answer "can we reuse existing code instead of writing every outstanding filesystem from scratch?"

TotalImage (`../TotalImage`)

What it is: an MIT-licensed disk-image editor written in C# / .NET 10 / WinForms. MIT is compatible with our AGPL-3.0 (port with attribution), but it is a different language — nothing links or imports; every reused line must be manually ported to Rust.
Filesystem overlap: it implements FAT12/16/32, exFAT, NTFS, ISO9660, UDF, and IMGFS (Windows CE). We already have everything except UDF and IMGFS, neither of which is in MiSTer scope. It contains none of the outstanding MiSTer filesystems (no CP/M, CBM DOS, ADFS, Human68k, QDOS, OS-9, etc.) — it is a PC/DOS/Windows-centric tool.
The one genuinely portable gem: FileSystems/FAT/FatFactory.cs does robust BPB-less FAT detection — infers geometry from image size + media descriptor + dual-FAT validation (4 disambiguation rounds), tries the BPB at alternate offsets (0x04 Zenith Z-100, 0x50 Apricot), and special-cases Acorn-DOS-800K and Victor 9000. Paired with the geometry table in DiskGeometries/FloppyGeometry.cs. Our src/fs/fat.rs::open currently requires a BPB at the standard offset with no fallback, so this is a real robustness gap-filler — but it only helps cores we already support (raw Atari ST .st, MSX .dsk, odd PC floppies). It does nothing for the outstanding non-FAT cores.
IMZ note: Containers/ImzContainer.cs confirms an unencrypted WinImage IMZ is just a ZIP with a single entry + zip comment. It does not touch the encrypted IMZ (MD5 + Rijndael) tracked in imz_encryption.md.
Verdict: not a "use most of their code" opportunity. Treat as a narrow reference: port the BPB-less FAT detection + geometry table (with MIT attribution) if/when we harden raw-floppy FAT handling. Everything else either overlaps what we have or is out of scope.

Pure-Rust crates (the bigger lever)

All three are MIT / MIT-OR-Apache, so they can be vendored as dependencies or ported with attribution under our AGPL.

Crate	License	Covers	MiSTer cores unlocked	Maturity
a2kit (`dfgordon/a2kit`)	MIT	CP/M 1/2/3, Apple DOS 3.3, ProDOS, Pascal FS, FAT; containers 2MG/DSK/DO/PO/IMD/IMG/NIB/TD0/WOZ	Apple-II DOS 3.3 (our gap) + CP/M family: Amstrad, AmstradPCW, TatungEinstein, SVI328, Altair8800, MultiComp, ZX +3DOS	Active, v4.4.2
cbm (`simmons/cbm`)	MIT/Apache	D64/D71/D81 read/write/format/rename	C64, C128, C16, VIC20 (not PET D80/D82)	Complete but dormant
fluxfox (`dbalsom/fluxfox`)	MIT	Container/track layer: TD0, IMD, HFE, 86F, IPF, SCP, raw IMG/DSK/ADF/ST + Amiga/Mac/Atari ST/Apple GCR	The shared container-decode infra layer feeding the superfloppy path	Active, ~150 stars

Caveats to verify before depending on them:

a2kit CP/M may be Apple-CP/M-centric — confirm it ingests arbitrary per-machine disk parameter blocks (Amstrad/PCW/Einstein geometries) before counting it for the CP/M cores.
fluxfox .d88 support is ambiguous (crate docs omit it; a secondary source claimed it) — matters for PC88 / X68000 floppies.

Per-filesystem crate availability matrix

Outstanding filesystem	Cores	Rust crate?	Best path
CP/M	Amstrad, PCW, Einstein, SVI328, Altair, MultiComp, ZX+3	a2kit (verify DPBs)	Vendor/port a2kit
CBM DOS	C64, C128, C16, VIC20	cbm	Vendor cbm
CBM DOS (D80/D82)	PET2001	No	Extend cbm or ground-up
Apple DOS 3.3	Apple-II	a2kit	Vendor/port a2kit
Container decode (TD0/IMD/ADF/ST/MSA)	many	fluxfox	Vendor fluxfox
Container `.d88`	PC88, X68000	fluxfox (uncertain)	Verify, else custom
Atari DOS (`.atr`)	Atari800	No (`atrfs` is Go/Python)	Ground-up; reference atrfs spec
Human68k	X68000	No (`dis68k`/`fathuman` are C/Go)	FAT-derived; our FAT + custom dir layer
ADFS / FileCore	Archie, BBC/Electron ADFS	No	Ground-up; ref OpenAcornExplorer, Linux adfs
QDOS	QL	No	Ground-up
OS-9 RBF / RS-DOS / DragonDOS	CoCo2, CoCo3	No	Ground-up
TRS-80 (TRSDOS/LDOS)	TRS-80	No	Ground-up
Oric Jasmin	Oric	Yes	Done (`src/fs/oric.rs`)
Sedoric (Oric DOS)	Oric	No	Ground-up
N88-BASIC	PC88	No	Ground-up
Sharp MZ FD	SharpMZ	No	Ground-up
EOS	ColecoAdam	No	Ground-up (read-only)
TI-99 FS	TI-99_4A	No	Ground-up
ANDOS/CSIDOS, MicroDOS, Specialist-MX	BK0011M, Vector-06C, Specialist	No	Ground-up (niche)

Revised takeaway

The crates change the build-vs-reuse math for the highest-payoff targets: a2kit can cover the entire CP/M family plus our Apple DOS 3.3 gap, cbm covers four Commodore cores outright, and fluxfox supplies the container-decode infrastructure piece budgeted above. The long tail (ADFS, Human68k, QDOS, OS-9, TRS-80, and the niche/Soviet filesystems) still has no Rust prior art and remains ground-up work. TotalImage is a minor reference for hardening FAT floppy detection, not a reuse source for the outstanding cores.