While resourceful owners could accomplish a lot with the 1K or 2K of RAM built in to their computers, more serious uses required more RAM. Sinclair and Timex offered 16K RAM units for the ZX80, ZX81 and TS 1000 computers. For many, that was enough.
A huge number of expansion RAM packs were produced for the Sinclair computers. Some extended beyond the default 16K, others claimed to address the “RAM pack wobble” problem and others made RAM available in special locations or configurations or had other special features.
| Name | Description | Computers |
|---|---|---|
| 1-3K Memory Expansion | Uses static RAM. | Sinclair ZX80 |
| 16-32-48K expanda RAM | Fits inside case. | Timex/Sinclair 1000 |
| 16K or 32K RAM Plans | Plans to expand 1K model to 16K or ZX81 with 16K to 32K for under $30. Fits inside ZX81. | Sinclair ZX81, Timex/Sinclair 1000 |
| 16K RAM | Sinclair ZX80, Timex/Sinclair 1000 | |
| 16K RAM | Gold-plated connectors and power LED. Manufactured by Indescomp. | Timex/Sinclair 1000 |
| 16K RAM (internal) | Internal RAM expansion for keyboard. | Timex/Sinclair 1000 |
| 16K RAM Pack | No enclosure RAM pack. | Timex/Sinclair 1000 |
| 16K RAM Pack | Timex/Sinclair 1000 | |
| 16K RAM Pack | Timex/Sinclair 1000 | |
| 16K RAM Pack | Timex/Sinclair 1000 | |
| 16K RAM Pack | Timex/Sinclair 1000 | |
| 16K RAM Pack | Expansion for the Compu-board system. | Timex/Sinclair 1000 |
| 16K RAM Pack | Available with or without a case. | Timex/Sinclair 1000 |
| 16K RAM Pack | Timex/Sinclair 1000 | |
| 16K RAM Pack | Timex/Sinclair 1000 | |
| 16K RAM Pack | Works on Sinclair power supply. | Timex/Sinclair 1000 |
| 16K RAM Pack | Highly crash resistant RAM pack that can be mounted inside the computer under the keyboard or plugged into the rear connector. Requires no extra power supply; comes with a special high pressure edge connector. | Timex/Sinclair 1000 |
| 16K RAM Pack | Injection molded plastic case; overcomes wobble and disconnection problems characteristic of other units; optional extra is a keyboard sounder giving audible feedback when a key is pressed. | Timex/Sinclair 1000 |
| 16K RAM Pack | RAM pack physically similar to TS 1016. Claims not to suffer from wobble. | Timex/Sinclair 1000 |
| 16K RAM Pack | Expandable to 32K. | Sinclair ZX80, Timex/Sinclair 1000 |
| 16K RAM plus Expansion Board | 3 slots with extra power supply. 4K or 16K. | MicroAce |
| 1K RAM Board | Static RAM; expands internal memory to 2K. | Sinclair ZX80 |
| 256K RAM disk | Upgrade to disk interface. Can be configured as RAM disk or port-mapped in 64K banks shadowing the cartridge bank. | Timex/Sinclair 2068 |
| 2K Memory Upgrade | Kit to increase the ZX81 to 2K. | Sinclair ZX81 |
| 2K RAM Board | Static RAM; expands internal memory to 3K. | Sinclair ZX80 |
| 2K RAM Pack | Static RAM expansion; works with built-in RAM. | Sinclair ZX80, Sinclair ZX81, Timex/Sinclair 1000 |
| 2K RAM Upgrade | Upgrade for 1K ZX81. Includes 2K RAM chip, socket, jumper and instructions. | Sinclair ZX81 |
| 2K RAM Upgrade | Internal upgrade; replaces existing RAM chips. | Sinclair ZX81 |
| 2K to 24K Memory Expansion | Plans to expand memory up to 24K, using 2K RAM chips, placed anywhere from 8192 to 32768. | Timex/Sinclair 1000 |
| 32K and 32K/64K Non-Volatile Memory RAM Board/Cartridges | Plugs into the TS2068 cartridge slot. On board battery keeps it alive even when you turn the computer off. Switch selectable for use in the DOCK or EXROM banks with no mods to the computer. Write protect switch lets you use memory like an EPROM. Run your own plug-in BASIC programs. Detailed instructions include utilities | Timex/Sinclair 2068 |
| 32K Internal RAM Modification | 32k RAM inside the 2068, in the upper half of the DOCK and EXROM bank. RAM is active in the DOCK and/or EXROM bank, allowing user to save files that reside in the DOCK bank. Can also load files directly into this RAM from tape. Switch to disable the RAM in the DOCK bank so | Timex/Sinclair 2068 |
| 32K RAM | Gold-plated connectors and power LED. Manufactured by Indescomp. | Timex/Sinclair 1000 |
| 32K RAM cartridge | Expansion RAM, plugs into dock slot. | Timex/Sinclair 2068 |
| 32K RAM Pack | Expandable to 64K. RKL joystick systems can be added to this unit. | Sinclair ZX80, Timex/Sinclair 1000 |
| 32K RAM Piggy-Back | Can be used standalone or with a 16K RAM for a total of 48K. | Timex/Sinclair 1000 |
| 3K RAM Board | Static RAM; expands internal memory to 4K. | Sinclair ZX80, Sinclair ZX81, Timex/Sinclair 1000 |
| 48K Memory Extension | Allows ZX81 to run 48K Basic programs including up to 16K of assembly code. ZX81 sits on custom built case containing the Memotech. | Sinclair ZX81, Timex/Sinclair 1000 |
| 48K RAM for TS2000 | Announced before 2068 launched. Manufacturer assumed 2068 would be identical to Spectrum. | Timex/Sinclair 2068 |
| 48K RAM Pack | Sinclair ZX80, Timex/Sinclair 1000 | |
| 4K RAM Pack | Static RAM expansion; works with built-in RAM. | Sinclair ZX80, Sinclair ZX81, Timex/Sinclair 1000 |
| 64K Dynamic RAM | 64K DRAM board for the TS1000, TS1500 or ZX81. Special features of this memory include: 8-12K on/off switch 12-16K on/off switch two banks of 8K ram available mapped 8-16K (Bank A/B switch) and 48-64K on/off switch | Timex/Sinclair 1000 |
| 64K RAM | Gold-plated connectors and power LED. Manufactured by Indescomp. | Timex/Sinclair 1000 |
| 64K RAM (internal) | Internal RAM expansion for keyboard. | Sinclair ZX81 |
| 64K RAM Pack | Sinclair ZX80, Sinclair ZX81, Timex/Sinclair 1000 | |
| 64K RAM Pack | No enclosure RAM pack. 4K pages can be switched off. | Timex/Sinclair 1000 |
| 64K RAM Pack | Timex/Sinclair 1000 | |
| 64K RAM Pack | Timex/Sinclair 1000 | |
| 64K RAM Pack | Available with or without a case. 8-16K area available. | Timex/Sinclair 1000 |
| 64K RAM Pack | Metal case, snug fit for no wobble. | Timex/Sinclair 1000 |
| 64K RAM Pack | Expansion for the Compu-board system. | Sinclair ZX81, Timex/Sinclair 1000 |
| 64K RAM Pack | Timex/Sinclair 1000 | |
| 64K RAM Pack | Timex/Sinclair 1000 | |
| 64K RAM Pack | Timex/Sinclair 1000 | |
| 64K RAM Pack | Self-contained memory expander, housed in metal. | Timex/Sinclair 1000 |
| 64K RAM Pack | RAM pack similar in shape to the TS 1016. Claims not to suffer from wobble. | Timex/Sinclair 1000 |
| 64KT/64KZ | 64K RAM upgrades which mount inside the TS 1000 or ZX81. Installs in a minute with no soldering, and easy to follow instructions. Disable the 10-12K, 8-12K, or 8-16K areas of memory with a switch. Models specific to the ZX81 and TS 1000. | Sinclair ZX81, Timex/Sinclair 1000 |
| 6K memory (internal) | Add 4K or 6K RAM internally. | Timex/Sinclair 1000 |
| 8K RAM pack | Timex/Sinclair 1000 | |
| Add on RAM for ZX80 instructions | Complete schematic, parts list, sources, and how-to. | Sinclair ZX80 |
| Complete Memory Plans | Documentation packet that covers memory pack troubleshooting. Includes plans for constructing your own memory pack, EPROM reader and extending the memory of the 16K RAM pack up to 64K. | Timex/Sinclair 1000 |
| CRAMIC-81 | 16K RAM pack using CMOS 6116 static RAM chips for permanent data retention. Data can be stored almost indefinitely and loaded almost instantly with virtually zero chance of error. A long life (10 years) lithium battery supplies power in standby mode. In the active mode, power is taken from the ZX81. Used on its own, | Timex/Sinclair 1000 |
| Decoder | Fits inside the ZX80/ZX81 and remaps internal RAM to 8-9K or 9-10K. For use with external RAM pack. | Sinclair ZX80, Sinclair ZX81 |
| Delta Device | Non-volatile memory designed by Wilf Rigter. 32K RAM with Rigter Operating System (ROS). File-handling system in less than 600 bytes. Includes: DIRECTORY: displays all programs stored in memory by name and length in bytes. 44 entries per directory. SAVE: transfers BASIC programs, variables, and machine code to storage. Works in conjunction with the NAME/RENAME features. | Timex/Sinclair 1000 |
| Downsway 16K RAM Pack | Fully cased and compatible RAM pack. | Timex/Sinclair 1000 |
| Downsway 64K Memory | Timex/Sinclair 1000 | |
| Econo Tech 16K RAM Pack | Budget model 16K RAM supplied without case, gold-plated contacts. Designed to prevent wobble. | Timex/Sinclair 1000 |
| FD16K RAM | Memory expansion that fits inside the Fuller keyboard and requires the Fuller motherboard. | Timex/Sinclair 1000 |
| FD64K RAM | Memory expansion that fits inside the Fuller keyboard and requires the Fuller motherboard. | Timex/Sinclair 1000 |
| Hardwire RAM Pack | Kit and instructions to permanently connect RAM pack to computer. | Timex/Sinclair 1000 |
| Hunter 8K Nonvolatile CMOS RAM/EPROM | Up to 8K RAM or EPROM; works with 16K RAM packs. Store your own system utilities or build a library of machine language routines. Can be used with any ROM or RAM. | Timex/Sinclair 1000 |
| Internal 16K RAM Expansion | PC board and instructions. Instructions, $7.95. | Sinclair ZX81 |
| Jigsaw 16K RAM | Can be used with Jigsaw 32K Plus to upgrade to 48K. LED power indicator. | Timex/Sinclair 1000 |
| Jigsaw 32K RAM | 32K RAM operates in tandem with a 16K to provide up to 48K RAM. Compatible with the Data-Assette ZX99. LED power indicator. | Timex/Sinclair 1000 |
| Jigsaw 64K RAM | 64K RAM extends usable memory to 56K. LED power indicator. | Timex/Sinclair 1000 |
| LARKEN RAMdisk | Expands the 2068 with up to 256K of nonvolatile RAM. Includes LKDOS Extended BASIC cartridge and memory board that attaches to expansion port. LKDOS uses standard BASIC commands (LOAD, CAT, SAVE, etc) to operate the RAM disk. Uses 32K (62256) CMOS RAM chips backed up with a battery; comes with 64K. Compatible with Spectrum, OS-64 | Timex/Sinclair 2068 |
| M-16 Memory Module | Stackable with Sinclair RAM or other M-16 modules to 48K. | Sinclair ZX80, Timex/Sinclair 1000 |
| M-48 Memory Module | 48K RAM module. | Sinclair ZX81, Timex/Sinclair 1000 |
| M-64 Memory Module | Low power, no extra power supply required. Area from 8-16K can be switched out in 2K increments to accommodate memory-mapped peripherals, EPROMs, etc. | Timex/Sinclair 1000 |
| MEMIC-81 | Contains one or two 2K (6116) CMOS RAM chips. Memory is addressed into the ROM area from 8K-16K in the ZX-81 memory map. The address at which each chip appears can be adjusted to any 2K section within that area. Lithium battery in the unit provides a back-up power while the computer is switched off. | Timex/Sinclair 1000 |
| Memopak 16K | 16K RAM unit expansion capabilities through its piggy back connection and is fully compatible with Timex or Memotech 16Ks to give 32K RAM. | Timex/Sinclair 1000 |
| Memopak 32K | The 32K Memopak could be combined with a 16K RAM for 48K RAM. It was initially incompatible with the 2040 printer. | Timex/Sinclair 1000 |
| Memopak 64K | Timex/Sinclair 1000 | |
| Memory board with I/O | 16K or 32K and two 8-bit LS TTL input ports and two 8-bit latching output ports. | Timex/Sinclair 1000 |
| Minimap | Memory mapping device to expand address space from 64K bytes to 1 megabyte. Organized into vertical 64K pages. Up to 16 pages can be supported. All memory can be dynamically defined from within a program, allowing (for example) a program in one segment to manipulate the contents of various data segments. A module in the | Timex/Sinclair 1000 |
| MX-16 16K RAM | Expansion plus power supply. | Timex/Sinclair 1000 |
| MX-16 RAM | Expansion RAM pack. | Timex/Sinclair 1000 |
| MX-48 RAM | 48K expansion memory; with power supply. | Timex/Sinclair 1000 |
| MZ512K | 512K RAM expansion for the Sinclair QL featuring no wait-state memory and full through port. | Sinclair QL |
| QS 16K RAM | Cased dynamic RAM expansion. | Timex/Sinclair 1000 |
| RAM 08 | Low cost memory expandable from 2K to 8K. Located in an address space not used by BASIC. Ideal for data or machine coded routine shared by second program. A module in the BASICare Modular Expansion System. | Timex/Sinclair 1000 |
| RAM 16 | 16K memory module. On-board address decoding permits simultaneous use of many RAM 16 modules in conjunction with Minimap. A module in the BASICare Modular Expansion System. | Timex/Sinclair 1000 |
| RAM 64 | Arranged in 4 blocks of 16K; all can be used under MINIMAP control. On board address decoding allows simultaneous use of many modules with MINIMAP. A module in the BASICare Modular Expansion System. | Timex/Sinclair 1000 |
| RAM Adaptor Board | Adapts Sinclair RAM pack to fit inside Fuller case. | Timex/Sinclair 1000 |
| RAM for TS2000 | Announced before 2068 launched. Manufacturer assumed 2068 would be identical to Spectrum. | Timex/Sinclair 2068 |
| RAMPAK 16 | Flat RAM module. 16K. | Timex/Sinclair 1000 |
| RAMPORT | Integrated expansion system. Analog, digital I/O ports and 16K RAM expansion on one card. | Timex/Sinclair 1000 |
| SCRAM Board | Improved version of Hunter board. Comes with battery-backup to make memory non-volatile. Developed with Larken Electronics to support Silicon Mountain’s WRX-16-based high-resolution software. Mapped in the 8K from 8-16K block. Can be re-mapped to 16-24K or 24-32K. Three SCRAM boards can provide 24K RAM for the ZX81 or 40K for the TS 1500. BOARD ENABLE | Timex/Sinclair 1000 |
| SCRAM-Wich | SCRAM board with two 8K static RAM chips, mapped to the normal 16-32K RAM region. Top 8K can be switched out in 2K blocks, allowing you to keep machine-code above RAMTOP. | Timex/Sinclair 1000 |
| SIN 16 | Efficient design, uses less power. Gold-plated, heavy-duty connector prevents glitches. | Timex/Sinclair 1000 |
| Strip down | Prevent RAM wobble. | Timex/Sinclair 1000 |
| SUPER SIN64 64K RAM | 8-16K range can switch in/out. | Timex/Sinclair 1000 |
| The Incremental 1.1 | Fits inside computer; plugs in, no soldering; up to 16K in increments of 2K. Uses 6116 static RAM. | Timex/Sinclair 1000 |
| The Lip 16K RAM | “The LIP” locks on to prevent the wobbles. | Timex/Sinclair 1000 |
| TS 1016 RAM pack | Timex’s version of the Sinclair ZX81 16K RAM pack for the Timex/Sinclair 1000. This, and the Sinclair unit, were famous for “wobble,” a condition that resulted in resetting the computer and loss of memory contents. Users overcame this problem with a variety of solutions, including Velcro between the computer and RAM pack, oversized rubber bands, | Timex/Sinclair 1000 |
| TS 1016S RAM Pack | Prototype RAM expansion module. Internal circuit board marked “TS-1032 REV A.” Has 16 AM9016EPC 16K x 1 bit RAM chips, total of 32K RAM. Date codes on all chips are 1982, the latest is the 50th week of 1982. Only one confirmed to exist. From Eric Johnson’s collection. | Timex/Sinclair 1000 |
| UM-16 16K RAM Pack | “Ultimate memory” RAM pack. Battery backup, reset switch, PROM/ROM socket. | Timex/Sinclair 1000 |
| UM-64 64K RAM Pack | 64K RAM pack with additional features. 8-16K area selectable in 2K increments. EPROM socket for 2K/4K. Battery backup (6 AA batteries) powers RAM pack and computer for up to 30 minutes. ROM-RAM transfer: copy Timex ROM into the 0-8K area of RAM, flip a switch and operate out of RAM. Switch that only resets 16-32K | Timex/Sinclair 1000 |
| ZX-Panda | Contoured case fits snugly against the rear of the computer. LED power indicator. Expandable to 32K with plug-in module that fits inside the existing case. | Timex/Sinclair 1000 |
| ZX-Panda Expansion Module | Plug-in module for 16K Panda, extending the memory to 32K. | Timex/Sinclair 1000 |
| ZX81 2K upgrade | Kit including instructions and IC socket. | Sinclair ZX81 |
| ZX81 2K Upgrade Kit | Double on-board memory to 2K. | Sinclair ZX81 |