can a UDMA card be used in a non-UDMA device?

[mrkgoo]

Basically, I want to know if the San Disk Extreme IV UDMA can be used in a 40D. I know it won't be able to access the extra speed, but it will still work, won't it? There's no such thing as a UDMA-ONLY card?

I only ask because I see CF Extreme IV with and without UDMA added to the name afterwards, and was wondering if the latest ExtremeIV was like an ONLY UDMA or something.

I know it won't get the speeds for the 40D, but for the current rebates, it might be worth getting the Extreme IV for better future compatibility (I'm not one to normally go for future-proofing, but the rebates make it pretty worthwhile).

[swalter]

Yes, UDMA is an optional mode for compact flash and all cards are backwards compatible. I've used Sandisk Extreme IV cards in my 20D.

Wikipedia has a lot more technical details
http://en.wikipedia.org/wiki/Compact_flash

[mrkgoo]

Thanks for the info.

[overclock]

Get a UDMA reader as well. The transfer speeds are amazing with a UDMA reader. I have both a FireWire and a USB UDMA reader and both rock.