This just sold today on eBay for EUR 70. Look pretty neat but I couldn't find any information about it, other than this eBay listing
RAM/EEPROM pack
software loader
ZX81 Extension Board contains 16kB external RAM and Software Loader OS1510/2 (Hardware version 2.0) with 8 games for ZX81 / Timex1000. OS1510/2 allows you to select one of 8 available games, load and run them. RESET button and red power LED are onboard available as well.
Flashing Yellow LED is signalizing active LOAD process.
OS1510/2 is a next generation of the famous rare TIMEX Sinclair TS1510 ROM cartridge loader. TS1510 allows you to load a game / software from ROM-cartridge attached to the TS1510 loader. Big disadvantage is, that before changing ROM-cartridge, the computer always needs to be switched off. With OS1510/2 it is enough to press RESET and select another available game.
Following games are available on the board (SET 1):
1) Pinball
2) Reversi
3) 3D Monster Maze (Tyrannosaurus REX)
4) Manic Miner (high resolution game for ZX81)
5) Frogs
6) Flight Simulator
7) Puckman
8) Super Chess
When the computer is switched on with the OS1510/2 module inserted, happens nothing. 16kB RAM is immediately available. Available RAM can be easily checked by typing: PRINT PEEK 16389
ZX81 will response with 68 for 1kB RAM, 72 for 2kB RAM and 128 for 16kB RAM.
The ROM-loader can be initiated e.g. with following BASIC command:
RAND USR 8192.
With this version of the loader is the LOAD process fast – maximal load time is less than 10 seconds.
The loader itself is a board with 8kB EEPROM memory containing OS1510/2 firmware and a Z80-PIO chip interfacing SPI EEPROM memory with ZX81 games.
In addition, a RESET button is placed on the board and a red power LED indicating the presence of +5,0V power supply.
This listing contains the board with 16kB RAM extension and ROM Cartridge.
There is NO ZX81 included, even is shown on some pictures. The ZX81 is used just to demonstrate the connection of the board to ZX81 and the functionality. But as I wrote: THERE IS NO ZX81 computer included.
was advertised as a version of the [rare] TIMEX Sinclair TS1510 ROM cartridge loader, but looks nothing like the TS1510 CLONE which is a 2 board set, more similar to the original with its removable upright cartridge board
