RAM expansion & RAMdisk
RAM expansion, memory packs, and RAMdisk solutions.
37 threads · 335 messages · 2004-07-06 → 2026-05-24
Across both eras, the Larken 256K RamDisk is the gravitational center of the TS2068 RAM-expansion discussion. The Yahoo years featured hands-on assembly help — which side is the component side, how to source the 1K/4.7K resistor pack, which 32Kx8 SRAMs are interchangeable, and that the correct DOS cartridge depends on the host interface (L3 for Larken, R3 for Ramex, O3 for Oliger, A3 for Aerco). That practical build knowledge carried straight into the groups.io era, where Neil C. and ChazzMan undertook a full reverse-engineering of the original schematic (resolving the confusing "no order" A0-A14 labeling by recommending straight-through mapping) and laid out a new double-sided PCB, with David Anderson and Tim Horner consulting from the historical record.
Alongside Larken, both eras hosted ambitious internal-upgrade designs. In 2005 Jarek Adamski proposed a simple 512kB SRAM + 128kB PEROM upgrade with four SRAM configurations (64kB DOCK, top-32kB DOCK for Larken compatibility, 64kB EXROM for ZXVGS, top-32kB EXROM), while Jeff Burrell countered with a more flexible CPLD-based 512K/512K mapper. By 2014 Don Dindang had designed a TS-2068 128K board that emulated ZX Spectrum +2/+3 memory paging, paired with Eduardo Fuentes's AY-3-8910 ROM patches. That thread is the clearest hand-off to the modern era: Eduardo returned in 2023 with a new bank-switched expansion explicitly "inspired on the Larken RAM Disk," 8K-chunk-mappable across the full 0-64K address space — the missing piece Gustavo Pane needed to port real CP/M 2.2 (with the 64K Dock bank as TPA/CCP/BDOS/CBIOS and Home bank for I/O), targeting compatibility with the original Timex 160K and 640K floppy formats.
The groups.io era has also recovered and contextualized older Timex-era expansion hardware. Tom Woods's 32K/64K battery-backed NVRAM kit — used in the 1980s with Hot-Z and JLO disk system flow-through programs — was rediscovered in 2024 when Rich J. asked about it, prompting David Anderson to archive the manuals on archive.org. The TS1500's distinctive RAMRM signal (replacing the ZX81/TS1000 RAMCS*, documented in a 1983 Syntax newsletter) was explained anew in 2023: pulling RAMRM high lets internal RAM relocate to 16-32K so a TS1016 16K pack adds rather than replaces, yielding 32K total — with a 74LS245 octal bus transceiver partitioning the data bus. Modern projects like Carl Miles's TS1560 Bus Expansion Unit (2025) revisit battery-backed 64K RAM, WRX-compatible RAM, and ROM-in-RAM for the ZX81/TS1000/TS1500 platform.
The group has also clarified hard limits and persistent confusions. A 2006 Yahoo exchange settled "64K of RAM vs 64K of address space" (24K ROM + 40K RAM in the user's 2068). The 2023 thread on the manual's "16MB" claim traced it to Timex's planned 256-bank × 64K bank-switching scheme — never actually shipped beyond 256K DOCK-mapped modules, with Wes Brzozowski's "Mystery of the Missing 253" articles explaining why. ZX81/TS1000 RAM expansion past 32K remains tricky (Memotech's "ZX81 killer" Mempack 64K is notorious for frying machines), and WRX hi-res requires static RAM in specific 8K-16K window — modern boards like ZXpand+ build that mod in by default.
Key threads
- TS2068 simple upgrade: 512kB RAM, 128kB PEROM (archive.org) — Yahoo-era (2005) deep technical design by Jarek Adamski for an internal SRAM+PEROM upgrade with explicit Larken-ramdisk-compatible mode; Jeff Burrell counters with a CPLD-based 512K/512K mapper. Foundational reference for later expansion work.
- Larken Ramdisk (archive.org) — Yahoo-era (2011-12) practical build help — board orientation, resistor pack sourcing, interchangeable SRAM part numbers, and the canonical list of Larken/Ramex/Oliger/Aerco DOS cartridges (L3/R3/O3/A3). The shop-floor knowledge later threads build on.
- TS-2068 128K (archive.org) — Yahoo-era (2014-19) Don Dindang interface emulating ZX Spectrum +2/+3 memory paging, with Eduardo Fuentes's matching ROM patches for AY-3-8910 sound. The direct hand-off from Yahoo to groups.io: Eduardo returns in 2023 with the CP/M-oriented expansion.
- Larken 256K RamDisk (#576 on groups.io) — Groups.io-era (2021-22) reverse-engineering of the Larken schematic by Neil C. and ChazzMan, resolving the original drawing's confusing 'no order' A0-A14 labels and producing a new double-sided PCB layout — the modern continuation of the Yahoo Larken build threads.
- Real CP/M on TS-2068 (#4074 on groups.io) — Groups.io-era (2023-24) Eduardo Fuentes designs a Larken-inspired 64K bank-switched expansion (8K chunks across the full 0-64K range) specifically to host Gustavo Pane's CP/M 2.2 port — TPA/CCP/BDOS/CBIOS in the Dock bank, Home bank as CBIOS extension, targeting original Timex 160K/640K floppy formats.
- NVRAM PCB made by Tom Woods (#6910 on groups.io) — Groups.io-era (2024) recovery of Tom Woods's 1980s 32K/64K battery-backed NVRAM kit — Paul Holmgren's recollections of using it with Hot-Z and JLO disk flow-through programs, plus David Anderson archiving the original manuals on archive.org.
- TS1500 and 16k RAM pack (#3517 on groups.io) — Groups.io-era (2023) Carl Miles explains the TS1500's RAMRM signal (replacing ZX81/TS1000 RAMCS*) that lets internal RAM relocate to 16-32K so a TS1016 adds rather than replaces — citing the 1983 Syntax and Boston Computer Society newsletters. The definitive explanation of how TS1500 plus 16K pack gets to 32K.
- Good Morning and a strange question (#4769 on groups.io) — Groups.io-era (2023) settles the '16MB RAM' claim in the TS2068 manual — Timex's planned 256-bank × 64K scheme that never shipped past 256K DOCK-mapped modules, with David Anderson pointing to Wes Brzozowski's 'Mystery of the Missing 253' articles.
All threads (37)
↳ marks a thread where this topic begins mid-conversation — the link jumps to the message where it starts.
| 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 |
| ⭐ NVRAM PCB made by Tom Woods | 11 💬 | 2024-08-11 | RichJ |
| ⭐ WRX16 DEMO 📎 | 11 💬 | 2023-05-21 | Adam Trionfo |
| ⭐ VCF Southwest 📎 | 9 💬 | 2026-05-24 | Don Crawford |
| ⭐ 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 |
| ⭐ 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 |
| ⭐ TS-Pico Memory | 4 💬 | 2024-02-28 | Jeremiah Stoddard |
| ⭐ An external expansion to 128K RAM for TS/TC2068 📎 | 4 💬 | 2022-02-02 | Claudius |
| ⭐ 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 WRX compatible RAM for ZX81/TS1000 | 1 💬 | 2024-06-25 | David Anderson |
| ⭐ 32K for the ZX81/TS1000 | 1 💬 | 2026-03-02 | David Anderson |
| Good Morning and a strange question | 16 💬 | 2023-11-11 | Adam Trionfo |
| TS1000 keyboard repair options? ↳ #1993 📎 | 16 💬 | 2022-09-12 | Kevin Dorff |
| 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 |
| Memory chips | 5 💬 | 2006-02-28 | Senen Racki |
| Mystery zx81/TS1000 memory expansion 📎 | 5 💬 | 2023-12-31 | François Lanciault |
| Repurposing a ZX81 RAM pack | 4 💬 | 2024-06-24 | Ryan Gray |
| 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 |
| Larkin 256K RamDisk | 1 💬 | 2022-01-18 | Willie Jones |
| My idea for memory upgrade | 1 💬 | 2004-07-06 | Jarek Adamski |
| Memory calculator 📎 | 1 💬 | 2022-09-11 | David Anderson |
| the NVRAM PCB blank by Tom Woods | 1 💬 | 2024-08-11 | RichJ |
| Timex 16k Ram modules on ShopGoodWill | 1 💬 | 2019-09-24 | bob099 |