CRC2 checksum error: Looking for T22 EEPROM dump

[mxt3]

Hello,

I’ve undertaken a little restoration on a stripped T22 ThinkPad which I saved from the dumpster.

I am currently stuck on a 0188 CRC2 error. I’ve already come across the parallel port ‘dongle method’, where some pins are shorted in order to make the laptop skip some POST checks. It was reported to work with CRC1 errors. I didn’t have much luck with this method, however, with my CRC2 error.

My last resort therefore seems to be to rewrite the EEPROM with a known-working dump. Does someone have a dump, or can someone point me to where I can find one?

There is a slim chance that I didn’t perform the parallel port trick well, because I plugged jumper pins directly inside the parallel port. The wire gauge was a bit too loose, so one of the wires may have made bad contact. I tried multiple times though to make sure. If someone has experienced that the method also works against CRC2, I will reattempt. I then need to buy a parallel cable though to do it properly.

Any input or ideas are welcome.

[mxt3]

I got past the CRC2! I'm not exactly sure what happened, but will describe what I did for reference. In case someone else finds themselves in the same situation.

First, it is important to understand what the EEPROM stores. It stores the device/motherboard serial number, a GUID to uniquely identify the device configuration, the supervisor password (and perhaps also the MAC address?). It does not contain the actual BIOS, nor the BIOS configuration.

I found out that the Hardware Maintenance Diskette (HDM) can be used to rewrite serial numbers and generate a valid GUID. Therefore, it must also rewrite the CRC checksums in the EEPROM to maintain a valid configuration. My hope was thus to boot the HDM floppy, if at least it would boot. I hoped the BIOS would recognize the floppy and ignore the CRC checksum error during POST, as the floppy was apparently also used to configure replacement motherboards. These motherboards would also have had a blank EEPROM, and maybe therefore an invalid configuration.

After finding the HDM (version 1.69) somewhere on the internet ( ), I made my floppy. And indeed, the laptop booted the floppy!
I then selected the option to generate a GUID, which gave a message that a GUID already existed and that it checked the checksum.
When I rebooted, the CRC2 error was gone!

I'm not sure if the HDM automatically correct the CRC, or that it was because of selecting the GUID option in the HDM menu. Anyhow, these are the steps which I did. Hope it may help someone some day!