Is RAM Backward compatible?

[Talk2Me]

I want to put some additional RAM in some older computers at my son's school. They currently have 64Mb of PC-100. Is RAM backward compatible? PC100 is expensive because it's not used. Can I use PC-133? PC-266? Anything will help in these P2 computers. Thanks.

[Budfred]

PC-133 will generally work, but will run at the PC100 speed... I wouldn't try the PC-266...

[mjc]

PC66-100-133 all are the same physical size/layout. They are pretty much interchangeable. And based strictly on FSB speeds for naming. '

PC266 is the start of the next generation of RAM, it has a different size/layout than the single speed stuff. It won't even fit in the socket for pc100/etc so, no it isn't compatable.

[saphalline]

Talk2Me - Give us some more info about the systems before plunking down the money. It's true that RAM is mostly backwards compatible, but the way that SPD was used for SDRAM can make things more complex. I've seen many mobo's/systems that will only use PC100 and nothing else. They simply refuse to boot with PC133, even though technically it should be compatible.

The theoretical isn't always the practical...