The Apricot BIOS is in two parts - the "ROM" BIOS and the "RAM" BIOS. The ROM BIOS provides some very basic functionality which allows the machine to start up and load the RAM BIOS and the Operating System.
Before FLASH devices EPROMs were commonly used to store the ROM BIOS - as was the case with the Apricots. EPROMs can be written and erased. Controlled application of ultraviolet light erases an EPROM to 'all-ones'. Each byte can then have bits set to 'zeros' by an EPROM programmer.
The Apricot PC has two 2764 EPROMs - one for the high byte and one for the low byte (the Apricot had 16-bit busses unlike the original IBM PC since it used the 8086 instead of the 8088).
I do NOT recommend attempting to write the original EPROMs in your Apricot! If you want to upgrade the ROM BIOS version or you are simply trying to get your Apricot working, please use a new EPROM(s) to burn in case you need to put the originals back in!
Despite their apparent antiquity, EPROMs can easily be purchased from major electronics component suppliers.
You will need an EPROM programmer and EPROMs to program. In order to program an EPROM, it should be either new (should be blank already) or erased. UV light erases EPROMs. For reliable erasure, special EPROM erasing boxes with controlled UV exposures are recommended.
All the files are in Motorola HEX format. Any EEPROM programmer software should be able to load these files.
There are three files per EEPROM set. For example:
* pc_bios____001.txt - 1 line description of EEPROM + 1 line copied from the original label on the EEPROM. (This file is to help you - it doesn't mean anything to the EEPROM programmer software). * pc_bios_hi_001.txt - Motorola HEX format EEPROM contents for "HI" EEPROM. * pc_bios_lo_001.txt - Motorola HEX format EEPROM contents for "LO" EEPROM
Submissions welcome!! If you can supply a submission to the Apricot EEPROM library please email them to me, preferably in a ZIP file. I can convert between some different formats of HEX file if needed. Please do include in the email a transcript of the label stuck on the EPROMs. EPROMs read from dead computers also welcome! (The EPROM may well be fine even if the machine is dead).