Understanding CF Cards... Enlightening needed.

[Dathan Hight]

As best as I can figure, CF cards come in two flavors, PIO and UDMA with a couple proprietary enhancements in between (like sandisk ESP). I'm seeing PIO limited to 25MB/s... so anything faster has to be UDMA ??

The why: Costco has a deal on CF cards right now. The card in question is a Sandisk Ultra II 8GB for $32.00. The read/write speed on the card is 30MB/s (200x). At this speed does that make it a UDMA Enabled Card?

This appears to be a Costco only product (UPC is SDCFH-008G-AC11) so there isn't any real info on this particular card - but the packaging shows it to be manufactured in 2009.



What say you?

[Duke M.]

UDMA means Ultra DMA (Direct Memory Access). Its supposed to write faster.

I don't know if UDMA is really necessary. Regular CF cards over 66x should work in theory. 100x should be overkill and the Kingston 133x non-UDMA is one I'd like to try. I picked a 16Gig one up for $34. Might be garbage though.

A bigger issue is that there are a lot of counterfit cards out there and no way to know if they formatted it to show bigger capacity or faster speed than it actually has until you're in the middle of shooting.

My camera came with an Extreme II card. Lots of people are buying SanDisk Extreme IV. No one know yet were the line is drawn between a good saftey margin and throwing your money away.

[Cranky]

Cards are not DMA or PIO. They are ATA :-) DMA and PIO are modes that are offered by your computer's bus and are supported by the cards' built-in controllers. Treat a CF card like an HDD, and choose it in the similar manner.

Generally, if you multitask, then DMA is better, because the load on CPU is lower.

[jrod81]

I apologize for such a basic question but what do we look for when buying the cards for the 7d? What is the base level of knowledge to take into best buy, sears, wal-mart, etc that I need to know to make sure I buy the right thing for video on the 7d...

[ydgmdlu]

Just get the fastest card that you can afford, and you'll be fine. You'll find much better prices online, however. Something that's marked as "133x" or higher should work. I use the inexpensive Kingston cards.