Is pc-100 compatible with pc-66?

I am upgrading the RAM on a friend's Gateway. I was wondering if I purchased PC-100 RAM would it be compatible with the PC-66 already in the system? The Gateway online support nor the manual offer any specific instructions. I know that PC-100/133 are compatible, but I wanted to check before I buy the stick.

How much do you need? May have a couple of sticks of PC66 (64Mb each I think) lying around gathering dust. I know that they were run at 100MHz and can't guarantee that they even work. If you are interested PM or E-mail me and I will test them out and bag them up.
Tell your friend to buy you a drink instead, as I said it's doing nothing. So it's free to a good home, will have to test first as it would be stupid to send it without doing so. I live in the UK, so it might take a week or so

Wow, thanks for your generosity . I don't want you to go to any bother though. I can pick up a stick of 128Mb for about $15 locally. It's not worth it for you to spend your schillings (sp?) to send them across the pond, when I can pick it up for so cheap here. Thanks for the offer, you're a real mate.

It wouldn't cost much to pop them in a Jiffy Bag. Just watch out on RAM prices they are creeping up again. BTW we spend Pounds and Pennies this side of the Pond. As I said, they are gathering dust and the only piece of kit I have that takes SDRAM is a PII that runs on a 100FSB. Offer stands free to good home E-mail or PM me, anyone??????? I CAN'T GIVE THEM AWAY lol

memory is downward compatible... pc133/100 should run on a pc 66 board.

Thanks Krome, that's what I wanted to know.

As long as they are DIMMs they'll work fine.