I've been scanning the archives both here an at DIY-EFI. I'm hoping someone can confirm / clarify a few things for me. For one, in several posts (here and at diy) I see lots of mention of EEPROMS in the same sentence as a 27C256 which is an EPROM. So I'm not surprised to see 29C256 referred to as an EEPROM. These are flash chips aren't they? Also, isn't the 28C256 an EEPROM? I have a 28C256 and it looks like I'll have to do a little rewiring to get it to work. I gather that the 29C256 is a pin compatible FLASH chip to the 27C256 EPROM. Am I correct?

-dnult

 

Uh, yeah. IIRC, the 27C* is typically a UV-EPROM, but some are WORMs. The 28* is a conventional E²PROM, and the 29C* is a CMOS Flash ROM or NVRAM device. Some of the better 29Cs have built in algorithms for sector erasure and protection.