CP/M
Running CP/M on Timex/Sinclair hardware.
16 threads · 217 messages · 2008-01-31 → 2026-08-25
The group's CP/M discussion keeps returning to one hardware fact: real CP/M needs 64K of plain RAM from address 0, and a stock TS2068 has ROM at 0–16383 and the display file at 16384–32767. Historically, the working route was the Timex FDD/FDD3000, which carried its own Z80 and RAM and ran a proprietary CP/M; Portuguese and Polish Timex users had CP/M from the early 1980s. Gustavo Pane still runs an FDD3 (silver) system with 64K on a US 2068 and has been building a CP/M 2.2 that reads the original Timex 40T SS (160K) and 80T DS (640K) formats, with the DOCK bank's 64K holding the CCP, BDOS and CBIOS. Joao Encarnado added that the FDD exposes its RS232 ports as TOS streams (OPEN #, PRINT #), and remembered FDD3000 CP/M as a very bare OS that needed PIP to copy files. On the history side, David Anderson found Lon Hildreth's November 1983 receipts for a trip from Hartford to Digital Research in San Jose to pitch a 2068 CP/M port, which never shipped.
In 2023, Clark Calkins' ZCP/M surfaced through a comment on David's site and a 1988 Computer Journal article. It was a ROM-based, CP/M-like OS for the TS1000 (in the 8K–16K space) written while Clark worked with A&J Microdrive and Exatron's Stringy Floppy. Clark joined the July 3, 2023 Zoom meeting, and Kevin hoped for an open-source release. In August 2023 Eduardo Fuentes proposed "Real CP/M on TS-2068": an expansion board, inspired by the Larken RAM disk, that maps RAM over the full 0–64K in 8K chunks (the ULA always reads the display from HOME RAM) with port-7 banking up to about 560K. Claudius offered to do the PCB, and Kevin suggested a boot-loader ROM. In 2026 Chris Nystrom asked about cartridge-based CP/M, and Jon suggested a PicoROM/PicoCartridge that supplies writable low RAM, possibly working with Eduardo's board.
Much of the tagged material is drift. The 2008 Yahoo threads (hi-res modes, the average-age thread, homemade programs) only touch CP/M through asides about 40-column CP/M, DivIDE and Kaypro games. Other threads that only mention CP/M in passing: the ABQ meeting (a Kaypro II that misbehaved at 5 MHz), "What makes Z80 special?" (Kildall's CP/M as part of the Z80's rise), the Shorter TS Pico Commands thread (Gustavo's 1985 link to a CP/M machine's hard disk), Jeffrey Burrell's Multicomp FPGA CP/M giveaway, the ATR8000 video, and the July 2022 article on CP/M's open-source status.
Key threads
- Real CP/M on TS-2068 (#682 on groups.io) — Eduardo's full-64K RAM expansion design and Gustavo's CP/M 2.2 using Timex disk formats and the DOCK bank.
- CP/M source available for the T/S2068?! (#965 on groups.io) — Sorts out Clark's ZCP/M (TS1000) from FDD3000 CP/M; Gustavo's FDD3 still runs, and the FDD's RS232 streams are explained.
- Timex Connection video (#971 on groups.io) — Where Clark Calkins' ZCP/M for the Timex first surfaced, leading to contact with him.
- Clark Calkins' CP/M-Like OS; was: UPDATED! Timex/Sinclair User Group Meeting Monday July 3 (#959 on groups.io) — Clark joins a meeting; his 1988 Computer Journal article on a ROM-based OS, plus recollections of FDD3000 CP/M.
- 40 years ago this weekend (#863 on groups.io) — Lon Hildreth's 1983 receipts document Timex's trip to Digital Research about porting CP/M to the 2068.
- CP/M on the Timex or Atari? (#1369 on groups.io) — First mention that Lon Hildreth took a 2068 and microdrives to Digital Research.
- TS2068 Cartridge development AI skill / docs / FAQ (#19 on groups.io) — 2026 proposal for cartridge-based CP/M using a Pico cartridge that supplies low RAM.
- 2068 with micro drive on ebay (#1371 on groups.io) — Notes that Portuguese and Polish Timex users had CP/M from the early 1980s, and that David tracked down Clark.
- Timex hi-resolution modes - CP/M (#1906 on groups.io) — Yahoo-era aside on the 64K requirement and 40-column CP/M; mostly a tape-sharing thread.
All threads (16)
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