i tried to upgrade myThinkpad 390x (PII 400MHz) with a 256 MB PC133 SO-DIMM module (in the other memoryslot there was a PC100SO-DIMM with 128MB). My 390x boots up and recognizes about 384MB ram. But when it comes to grub (the Linux operating system loader) then it hangs. If I boot my 390x only with the new 256MB PC133 module (after removing the old 128MB PC100 module) then i get even at the boot only a blackscreen.
As i read in the "i440bx chipset RAM module compatibility FAQ" there is the statement "Every PC133 Dimm is backwards compatible to PC100", seen at . But I also heard from someone that it is not possible to run an old i440bx based notebook with PC133(SO)DiMMs. Is it true? If not how can I upgrade my 390x with a 256MB PC133 SO-DIMM module? Do I have to use the 390x own bios hex editor?
The FAQ is not quite correct. A PC133 DIMM cannot always be be used instead of a PC100 DIMM. Other factors have to be taken into account such as the RAM organisation: I assume that you read the FAQ section on 256MB DIMMs. If these factors are OK, there is a good chance that it will work.
One reason why it may not work is that the BIOS may be written to read the DIMM speed from the SPD chip on the DIMM and to ignore the DIMM if it is not the correct speed, even if it is faster. This would be unusual but I have come across it on one occasion. As the BIOS appears to recognise all the RAM this does not look like your problem.
Have you tried booting to DOS and using a memory test program?