Don't jump to conclusions too fast. Many boards of that time require a specific method to disable flash chip write protection, and UniFlash just might not know about it. AWARD BIOSes have a generic interface that enables AWDFLASH to be board independent - but in bootblock-based BIOSes, this interface is not available while in recovery mode. Modern AWDFLASH versions can work around that some way (maybe it extracts the replacement BIOS into RAM to use its interface).

The TL866 supports your current chip. If you have one already at hand, just try re-flashing your current chip.

Furthermore: You get dropped into boot block because the BIOS calculates that the BIOS checksum is wrong. This can have either of two reasons: Maybe the BIOS chip contents is messed up. Or the computer is unreliable and mis-calculates the checksum of the BIOS. Especially as you talk about a failed Win98 boot, I suspect that maybe nothing is wrong with the BIOS chip at all, but your computer is unable to verify it. Problems like that can be caused by broken *RAM*. Before buying anything, try different RAM. If you have multiple RAM sticks, try them individually. You might also try to re-seat your processor. And finally, check the board for bulging caps.

I've done all the tests you advised (RAM swap, CPU and check for bad caps). Sadly issue is still present...

I should be able to borrow a TL866 from friend of mine, I'll try flash the current chip.

Flashing latest bios image fixed the issue.. yay!

I saved the 5€ new chip cost... but I had to buy the programmer! Well guess now I can try XT-IDE stuff with my IBM PS/Valuepoint.