TSU Meeting MONDAY — July 1, 2024

David Anderson, Ryan Gray, Joe, Gustavo, Tim Swenson, Jamie Macbeth

David opened with a quick TS-Pico update: Ricardo has wrapped the next round of firmware changes (midsummer, as promised) and a small group is now beta-testing them. The update is delivered as a couple of files dropped onto the SD card and flashed with the Pico powered from USB alone, which also opens the door to user-written extensions for the cartridge.

The bulk of the meeting was the ZX81/TS1000 "16K Spectrum-ish ROM." Ryan recapped the original observation that most of what makes a Spectrum a Spectrum lives in ROM, and after the prior meeting he found that a community project had already done exactly that — a 16K replacement ROM (initiated pre-2013, with a 2018 revision) that adds Spectrum-style BASIC (READ/DATA/RESTORE, OUT, OPEN/CLOSE, hi-res SCREEN) to a ZX81. Joe walked through actually building one: an Issue 3 board with the newer ULA, a 5V regulator and composite-video amplifier, a 16K-mask-ROM-to-EEPROM pinout fix with bodge wires for A12/A13 and chip-select, and a 16K static-RAM upgrade with traces cut and patched. First try produced scrambled video because the ROM steals DRAM-refresh time to drive hi-res; tightening the lead lengths fixed it. He demoed the running keyboard map, discussed memory map (Spectrum-style display file at 16K, no colour commands, extended keywords prefixed by REM >>) and Spectrum tape-format compatibility, including loading a Harlequin TAP off SD card. Group consensus: he'll need to push to 48K of RAM for it to be genuinely useful, and a switchable EPROM with the original 8K ROM is on the wish-list.

Ryan then explained his TS1500/TS2068 cartridge-image generator: a C utility that consumes a ZX81 .P file and emits a ROM image with a small loader (~100 bytes overhead), handling the 8K-block split for >8K programs, zeroing RAM down to RAMTOP, initialising system variables, generating a collapsed display file, and inserting variables via the ROM's own insert routine. A newer "tape-like" mode just memory-images the whole P-file. A companion utility interleaves multiple ROM images so Carl's dip-switch cartridges (alternating 8K blocks) can be burned in one shot. Joe brought out a ZX Profile / Quick Load ROM cart from the mid-'80s and the group speculated about how Quick Load patches SAVE/LOAD via routines mapped into the upper 8K. Carl's separate ZX80/81 dual-clone and the "ZX81 plus 38" board were also shown.

Gustavo gave a surprise demo of his long-running private TOSS (Timex OS) work: a new FDD-system rewrite that supports FAT filesystems directly (SD card, hard drive, Windows shared folders) with date/time on entries, plus his proprietary cycle-accurate TS2068 emulator (SCLD, banking, peripherals, single-step Z80 debugger — the same tool he used to develop the TS-Pico ROM before the hardware existed). He showed CAT, channel I/O to disk and serial, error handling, and free-space reporting. He's not ready to release the emulator publicly, but agreed it should at least be written up. Tim reminded the group that ZXZine is open for submissions — completed-project write-ups preferred, with binaries/PCBs shippable as zip attachments. Plans for printed hardcopies (11x17 saddle-stapled, ~100–150 copies, funded by the Bill Miller collection money) were discussed, along with possibly distributing flyers at VCF West (Aug 2–3) and reaching UK readers. Jamie Macbeth confirmed he's still working toward using the TS2068 to teach Z80 assembly at the college level. Next meeting: Sunday July 21, 2pm Eastern.

Highlights

Joe demos a ZX81 modded with a community 16K "Spectrum-ish" ROM and 16K static-RAM upgrade — running Harlequin TAP files off SD card
Ricardo's next TS-Pico firmware is feature-complete and now in small-group beta; updates ship as SD-card files flashable over USB
Gustavo reveals his private cycle-accurate TS2068 emulator and a new FAT-aware TOSS (FDD) build with SD/HDD/Windows-share support
Ryan walks through his C utility that turns a ZX81 .P file into a TS1500 cartridge ROM image, plus an interleaver for Carl's dip-switch carts
ZXZine is taking submissions for a printed hardcopy issue (~100–150 copies, 11x17 saddle-stapled) funded by the Bill Miller collection

Projects discussed: TS-Pico · "1068" — Enhanced TS1000 · Library Tape Archiving Process · The Bill Miller Collection Topics: TS1000 / ZX81 / TS1500 · Cartridges, EPROM & dumping · Hardware projects & new boards · Pico / modern interfaces (UnoDos, etc.) · Machine code, Z80 & assemblers · Newsletters & documentation

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