IBM 5170 - BIOS Revisions
On the 5170 motherboard, there are two BIOS ROM chips, one in socket U27 and the other in socket U47.
They are two 8-bit chips which, in combination, supply 16 bits to the IBM 5170's 16-bit data bus. Of the pair, U27 is the EVEN/LOW chip and U47 is the ODD/HIGH chip. Diagram here.
There were 3 revisions of the BIOS, differentiated by date (there are no version numbers).
The table below lists the dates, and the unique 7-digit IBM part numbers that are located on the top of the ROM chips.
The date format used is MM/DD/YY.
Some additional BIOS ROM part numbers are shown in figure 9 of the document at here.
Click here for content images (can be used to create replacements).
More information is shown here at the Vintage Computer Forums.
Supported by IBM was an upgrade from the 01/10/84 revision to the 06/10/85 revision. How do we know that? To owners of 5170s that had the type 1 motherboard, IBM made available a 30 MB hard drive upgrade kit, and that kit included 06/10/85 ROMs (required to support the 30 MB drive, of type 20).
It is unknown if IBM supported/endorsed an upgrade to the 11/15/85 revision. This upgrade is desirable to some 5170 owners, because it provides BIOS support for 1.44M diskette drives (e.g. ability to boot from a 1.44M diskette in A:). There is a small amount of concern here because a BIOS designed for an 8 MHz clocked motherboard is going into a 6 MHz clocked motherboard. I have not heard of any problems from people who have tried this upgrade. I tried it myself for a while, and I did not encounter any problem.
Besides an upgrade to the BIOS' shown above, you also have the option of upgrading to either an AMI BIOS or an Award BIOS or a Quadtel BIOS. Those BIOS' are available here.
Unlike with modern computers, you can not simply 'flash' a new BIOS onto the 5170 motherboard - you need to physically replace the two BIOS ROM chips. New BIOS ROM chips are normally created by 'burning' an image of the BIOS into suitable EPROM chips (via an EPROM programmer). Click here to see some people/companies that can supply and 'burn' EPROMs for you.
Known problem - POST error of 601
With the second (06/10/85) and third (11/15/85) BIOS revisions, removing the IBM Fixed Disk and Diskette Drive Adapter and substituting a third-party floppy controller results in a 601 error during POST (Power On Self Test).
There is something in those revisions that expects the IBM Fixed Disk and Diskette Drive Adapter.
The first BIOS revision (01/10/84) does not have the problem.