I have an old Toshiba Satellite L25-1215 that had a hynix 256mb 1rx16 PC2-4200S-444-12 in one of its two slots.
I researched and learned it was upgradable to 2gb max. So i installed one 1gb 2Rx16 PC2-5300S-555-12 in each slot. On boot up it gave me a black screen and didnt move. No dos, nothing. I went back to the original 256 and it worked fine. So, I decided just to try the One 1gb chip instead of both and it works.
Why wont it work with two 1gb chips if its upgradable to a max of 2gb?