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TSU Meeting MONDAY — December 2, 2024

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David Anderson, Tim Swenson, Gustavo, Adam Trionfo, Carl Miles, Ryan Gray, Paul Anderson, Keith, Joe, Mowgli

Tim Swenson and Gustavo gave a long status update on porting Boreal Basic (a Spectrum-BASIC superset that compiles to Z80 via a Python toolchain) to the TS2068. Two ROM-call mismatches between the Spectrum and the 2068 — reclaim (returning 0xFF on the 2068 and over-reclaiming, crashing string code) and the load/save XROM calls — were worked around by re-implementing the Spectrum routines locally in the .asm files; the STR$/VAL failures were also tracked down. Tim's strategy is to leave the Python compiler untouched and just swap Spectrum ROM addresses for the equivalent 2068 ones. He also replaced Boreal's hand-rolled CLS.asm with the 2068 ROM call so it works under OS64 (DFILE2). Performance is good except for math, which still goes through the floating-point calculator. They've been working from a new ~668-page ZX BASIC reference and a companion Z80 assembly book.

Carl Miles ran through his TS1510 clone work. He moved his PCB design from KiCad to EasyEDA, fixed the bugs in Claudius's earlier interface board (chip-select address-line swap, solder-mask over the edge connector that needed dremeling), and is selling the corrected interface and cartridge boards. A larger redesign uses a 4-megabit Toshiba EPROM (~$0.70 from Jameco) for up to 32 programs, selected by a hex rotary switch plus a two-digit LED that shows lower/upper bank and program number; jumpers let it also accept a 4Mbit flash chip. Ryan Gray's p2_1510 converter (in his zx81-utils GitHub repo) is producing the cartridge images — Crossy Road, etc. — and supports both a Timex-style loader and a tape-style loader (the latter generally working better). Carl is also working on a related ZX81/TS1000 ROM-replacement cartridge that borrows another author's external EEPROM board design and supports 16K ROMs (e.g. Sponzy, a stripped-down Spectrum ROM for the ZX81).

Keith, who happened to be on the call, confirmed he was the one who modified the Interface 1 ROM ~20 years ago to run on the TS2068 under the Warievo emulator (and an OS64 variant). Gustavo explained why that ROM can't be lifted into a real machine as-is: it relies on undocumented Z80 opcodes (ED FD etc.) that the emulator intercepts as hooks into a DOS TSR emulating the Interface 1 ULA and microdrive protocol. There was also AERCO talk (several members have 256K, 4-drive units) and a long aside on the Retro Games full-size ZX Spectrum recreation Carl received — HDMI out, accurate membrane keyboard, ~$123 shipped, not officially sold in the US.

Announcements: Tim is holding the next ZX zine until TS-Pico documentation lands, and wants the 1510 project written up for it. David offered to clear surplus Timex/Sinclair documentation from his basement at cost-of-shipping via a hidden category on his site, and shared scanning stats (1,635 issues, 12,498 indexed articles). A new attendee, also named Tim, introduced himself (ZX81 was his first machine at age 11). Joe demoed a built ZX-Wespi board. Tim Swenson reported on Vintage Computer Fest Berlin in October. Next meeting: Sunday December 15 at 2 pm — guest Jim will present TS1000-based computer art he made in college in the early 1980s, recreated in Python during the pandemic.

Highlights

  • Boreal Basic TS2068 port: reclaim/CLS/STR$/VAL issues worked around by replacing Spectrum ROM calls with local routines or 2068 equivalents
  • Carl's redesigned TS1510 interface and cartridge boards are on sale; a 32-program version with 4Mbit EPROM, hex rotary switch, and 7-segment bank/program display is in fabrication
  • Ryan's p2_1510 (in zx81-utils) converts tape programs into 1510 cartridge images, with a tape-style loader that's proving more reliable than the Timex-style one
  • Keith confirmed authorship of the Warievo Interface 1 ROM mod; it depends on undocumented Z80 opcodes used as emulator hooks, so it can't run on bare hardware
  • Next meeting Dec 15 at 2pm: guest Jim presents TS1000-based computer-art work from the early '80s, recreated in Python

Projects discussed: TS1510 Cartridge Interface Clone · TS-Pico · ZX-Wespi / Wespi-Nano Topics: TS1510 cartridge interface · Cartridges, EPROM & dumping · BASIC programming · Hardware projects & new boards · TS1000 / ZX81 / TS1500 · Pico / modern interfaces (UnoDos, etc.)

Summary generated from the meeting recording; the full transcript is kept in the group's private archive.