RAM expansion & RAMdisk
RAM expansion, memory packs, and RAMdisk solutions.
38 threads · 337 messages · 2004-07-06 → 2026-07-14
On the TS2068 the RAM-expansion story is really about the DOCK bank. As David Anderson explained in 2023, Timex's advertised 16 MB ceiling (256 banks of 64K under the bank-switching scheme, per Ryan Gray) never existed in practice, and Wes Brzozowski's articles explain why the planned scheme was flawed. Real-world expansions topped out around 256K and mapped into the DOCK, the Larken 256K RAMdisk above all. Back in 2006 the Yahoo-era list had to settle the basics: the 2068 has 64K of address space, not 64K of RAM, and 48K of it is RAM. In 2005 Jarek Adamski proposed a cheap internal 512K SRAM plus 128K PEROM upgrade using 74-series logic, with Larken-compatible top-32K DOCK paging and EXROM paging for ZXVGS, while Jeff Burrell argued for an Altera CPLD mapper with 8K-granular DOCK mapping that he had already prototyped. The 2014–2019 Yahoo thread on Don Dindang's TS-2068 128K interface, which implements Spectrum +2/+3 memory paging, came with Eduardo Fuentes's AY-enabled ROM adaptations.
The Larken RAMdisk ties the two eras together. In 2011–2012 Neil C. (pxx1) was building a bare Larken board from Eric Johnson's parts drawer with no documentation; Rod H supplied build tips (sockets for the SRAMs, a 10-pin resistor pack), and Jack Boatwright listed the Larken DOS cartridge variants (L3, R3, O3 and A3 for the Larken, Ramex, Oliger and Aerco interfaces). In 2021–2022 Neil restarted the effort on groups.io. David posted scans of the RAMdisk PCB, and ChazzMan began reverse-engineering it for a new double-sided PCB. David advised wiring the "no order" address lines straight through, and the team ran into pin mismatches in the decode logic. In 2023 Eduardo Fuentes built on the Larken design with a board that maps RAM across the whole 0–64K space in 8K chunks (the SCLD always displays from HOME RAM), with port-7 banking planned for up to 560K. The goal is real CP/M, which Gustavo Pane is implementing (CP/M 2.2 with the TPA in the 64K DOCK bank and the HOME bank as a CBIOS extension); Claudius joined in 2024 to design the hardware.
The groups.io era also turned up battery-backed and non-volatile memory. RichJ's search for Tom Woods's 32K/64K NVRAM board led David to point at archived manuals (including in Nite-Times News docs). Paul Holmgren recalled running Hot-Z from it and using it to move tape libraries onto JLO disks. David explained that DOCK cartridges are run-only, not a save target. A large share of this topic is the ZX81/TS1000/TS1500 side: Carl Miles on the TS1500's RAMRM line and the POKEs needed for the TS1016 pack, WRX hi-res needing static RAM (Larry Lorenson's WRX16 type-in from SyncWare News, SPONZY on a 16K-ROM zeddy), a dkTronics 64K pack that would not work, Memotech pack warnings, and Carl's planned TS1560 expansion with battery-backed 64K.
Several threads only drifted in: the TS-Pico bank-mapping discussion, a mystery FDD3000 "Timex Interface" find that also turned up a Larken unit, the TS1000 keyboard and repair threads (because of a 16K upgrade check), the Yahoo-archive reminiscence prompted by the Larken scans, a VCF Southwest show-and-tell with OpenSpand and memory upgrades, a 2006 giveaway of 41256 DRAM chips that suited the QL better than the 2068, and RichJ's TCC cartridge and DivIDE/esxDOS questions.
Key threads
- Larken 256K RamDisk (#1312 on groups.io) — groups.io-era effort by Neil C. and ChazzMan to document and reverse-engineer the Larken RAMdisk for a new PCB.
- Larken Ramdisk (#1666 on groups.io) — Yahoo-era (2011–12) attempt to assemble a bare Larken board from Eric Johnson's parts, with build tips and the L3/R3/O3/A3 Larken DOS variants.
- Real CP/M on TS-2068 (#682 on groups.io) — Eduardo Fuentes's Larken-inspired board mapping RAM over the full 64K in 8K chunks, alongside Gustavo Pane's CP/M 2.2 implementation.
- TS2068 simple upgrade: 512kB RAM, 128kB PEROM (#2142 on groups.io) — Jarek Adamski's 2005 internal 512K SRAM/PEROM design and Jeff Burrell's CPLD-mapper counter-proposal.
- TS-2068 128K (#1560 on groups.io) — Don Dindang's interface adding Spectrum +2/+3-style 128K memory paging to the 2068, with Eduardo's AY-enabled ROMs.
- Good Morning and a strange question (#861 on groups.io) — Explains the 16 MB marketing ceiling against the real 256K DOCK-mapped expansions, citing Wes Brzozowski's analysis.
- NVRAM PCB made by Tom Woods (#586 on groups.io) — Gathers the archived documentation and users' memories of Tom Woods's battery-backed 32K/64K NVRAM board.
- How's your memory? (#2096 on groups.io) — 2006 Yahoo-era clarification that the 2068 has 64K of address space but 48K of RAM.
- TS1500 and 16k RAM pack (#1036 on groups.io) — How the TS1500's RAMRM line and POKEs let a TS1016 pack coexist with internal RAM, plus WRX incompatibility of stock packs.
- Starting to design a TS1560 "Bus Expansion Unit" for the ZX81/TS1000/TS1500 - Brainstorming Ideas (#425 on groups.io) — Carl Miles's modern expansion design with battery-backed 64K RAM, ROM-in-RAM and HRG space for the ZX81 family.
All threads (38)
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| Thread | Msgs | Activity | Started by |
|---|---|---|---|
| ⭐ Larken 256K RamDisk 📎 | 40 💬 | 2022-06-28 | Neil C. |
| ⭐ Real CP/M on TS-2068 📎 | 34 💬 | 2024-03-27 | Eduardo Fuentes |
| ⭐ Larken Ramdisk 📎 | 28 💬 | 2012-10-10 | pxx1_2000_32724 |
| ⭐ Question about TS-Pico 📎 | 25 💬 | 2023-11-28 | Ricardo Calcagno |
| ⭐ Slightly off topic… TS1000 Help ↳ #6665 📎 | 24 💬 | 2024-06-23 | Patrick Leclerc |
| ⭐ Mystery Interface- Unable to Identify 📎 | 17 💬 | 2022-11-05 | David Anderson |
| ⭐ WRX16 DEMO 📎 | 11 💬 | 2023-05-21 | Adam Trionfo |
| ⭐ NVRAM PCB made by Tom Woods | 11 💬 | 2024-08-11 | RichJ |
| ⭐ TS-2068 128K | 9 💬 | 2019-08-03 | fuentesea |
| ⭐ Starting to design a TS1560 "Bus Expansion Unit" for the ZX81/TS1000/TS1500 - Br | 9 💬 | 2025-02-10 | David Anderson |
| ⭐ VCF Southwest 📎 | 9 💬 | 2026-05-24 | Don Crawford |
| ⭐ TS1500 and 16k RAM pack 📎 | 8 💬 | 2023-05-16 | Ryan Gray |
| ⭐ TCC cartridge and DivIDE 57c 📎 | 7 💬 | 2024-08-14 | RichJ |
| ⭐ TS2068 simple upgrade: 512kB RAM, 128kB PEROM | 5 💬 | 2005-08-14 | Jarek Adamski |
| ⭐ An external expansion to 128K RAM for TS/TC2068 📎 | 4 💬 | 2022-02-02 | Claudius |
| ⭐ TS-Pico Memory | 4 💬 | 2024-02-28 | Jeremiah Stoddard |
| ⭐ RAM to DOCK | 2 💬 | 2026-04-12 | Gus Lahoski |
| ⭐ follow up on ZX81 clone project | 2 💬 | 2024-07-11 | RichJ |
| ⭐ ZX81 Expanded Memory 📎 | 2 💬 | 2025-05-01 | Timothy Swenson |
| ⭐ 32K for the ZX81/TS1000 | 1 💬 | 2026-03-02 | David Anderson |
| ⭐ 32K WRX compatible RAM for ZX81/TS1000 | 1 💬 | 2024-06-25 | David Anderson |
| TS1000 keyboard repair options? ↳ #1993 📎 | 16 💬 | 2022-09-12 | Kevin Dorff |
| Good Morning and a strange question | 16 💬 | 2023-11-11 | Adam Trionfo |
| TIMEX SINCLAIR 1000 INTERFACES AT EBAY? 📎 | 8 💬 | 2022-10-18 | Luis Alberto D'Ardis |
| How's your memory? | 7 💬 | 2006-02-23 | James the Animal Tamer |
| Yahoo Groups Still Lurking About 📎 | 6 💬 | 2022-03-27 | Adam Trionfo |
| 16k ROM on a Zeddy 📎 | 6 💬 | 2024-06-24 | Ryan Gray |
| Mystery zx81/TS1000 memory expansion 📎 | 5 💬 | 2023-12-31 | François Lanciault |
| Memory chips | 5 💬 | 2006-02-28 | Senen Racki |
| Repurposing a ZX81 RAM pack | 4 💬 | 2024-06-24 | Ryan Gray |
| 256K Memory Expansion 📎 | 2 💬 | 2026-07-14 | Gus Lahoski |
| ZX80 RAM pack 📎 | 2 💬 | 2023-03-06 | Ryan Gray |
| Memory Upgrade and Disk or mass storage for 2068? | 2 💬 | 2007-01-25 | John Von Draugr |
| Memory calculator 📎 | 1 💬 | 2022-09-11 | David Anderson |
| Larkin 256K RamDisk | 1 💬 | 2022-01-18 | Willie Jones |
| My idea for memory upgrade | 1 💬 | 2004-07-06 | Jarek Adamski |
| Timex 16k Ram modules on ShopGoodWill | 1 💬 | 2019-09-24 | bob099 |
| the NVRAM PCB blank by Tom Woods | 1 💬 | 2024-08-11 | RichJ |