Description
EMS Memory was designed to overcome the memory limitations of the original IBM XT. The original architecture of the IBM XT has 20 address lines which gives a maximum memory space of 1MB. The top 384k is typically reserved for BIOS, leaving the lower 640k available for applications. In 1981, this seemed to be an obscene amount of memory. As time went on, this was not enough, but what to do when you have a hard limit on the amount of RAM you can address? The answer was EMS memory, co-developed by Intel, Microsoft & Lotus. While this was a nice solution, you must have an application which is aware of how to use type of RAM. Lotus 1-2-3 was one of the first, but later Windows, and many games and apps would make use of EMS to speed up gameplay and load more information into memory at once.
Purchase is for PCB only. Parts will need to be purchased separately, and assembled. The link below contains a full bill of materials to complete the build, as well as the instructions on how to set the board jumpers. We have updated the card to use a currently available off-the-shelf bracket. It is a Keystone 9202 and it uses Keystone 9900 screws, both can found at Mouser along with the other parts.
Lo-tech reference pages: wiki page and required LIM4 EMS driver (LTEMM.EXE).
You can download the driver and utility files here: 2MB-EMS-Files.zip
The through-hole parts have been changed to surface mount, please note these replacement part numbers for the bill of materials:
| Part | Value | Device | Package | Qty | Mouser |
|---|---|---|---|---|---|
| C16 | 10uF | Multilayer Ceramic Capacitors MLCC | 1210 (3225 metric) | 1 | 187-CL32A106KOJNNNE |
| JP1 | – | Headers & Wire Housings ECONOSTIK HEADER DR VT SMT 2X4 | PINHD-2X4 | 1 | 649-1012938390801ALF |
