Making ROMs

GLaBIOS BIOS ROM

The BIOS image is 8 KiB (same as the original PC, XT v1 and most clones). If your motherboard has an 8K ROM socket and you're using a larger E/EPROM it may be necessary to write the image repeated multiple times to work with the unused address lines. If your motherboard uses a 16K or 32K ROM, the image will need to either be repeated or to the last 8K block (starting at address FE00:0000) in the E/EPROM.

E/EPROM types

This page discusses options for suitable ROMs. TL866II Plus Programmer is a widely used option for writing these. Known tested and working IC types:

EPROMs:

• 2764 (8 KiB)

EEPROMs:

• ATMEL 28C64/28C64B (8 KiB)
• Winbond W27E257 (32 KiB - repeat image four times)

5150

The 5150 uses a 24 pin ROM. This page discusses options for adapters compatible types. The 23XX adapter mentioned has been tested with GLaBIOS and known to work.

ROM BASIC

If your motherboard uses a 32K ROM with BASIC ROM at 0xF600 you can extract the top 24K of U18 and write that into the new 32K ROM's 0x0000-0x5FFF space, with the GLaBIOS code starting at relative offset 0x6000.