Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm trying to breath some new life into an old Thinkpad X40 by replacing its HDD with a couple of CF cards. I've found a nice adapter will let me install two cards into the notebook's drive bay and plug them into the parallel ATA-3 bus.

The CF big cards are pretty expensive. The big, fast cards are even more expensive. I'd like to get one as fast as possible, but I don't see any point in buying cards that are faster than the IDE bus. Does anyone know what the maximum speed of that bus is? Google isn't helping me here.

share|improve this question

migrated from Apr 4 '12 at 18:27

This question came from our site for system and network administrators.

up vote 7 down vote accepted

This is a bit complicated because the ATA-3 spec was only a draft, never a final specification. Thus it's hard to say what version of the draft your system claims conformance with. The latest ATA-3 spec states a maximum PIO speed of 16.6MBps, and a maximum DMA speed of 33MBps.

That's the bus speeds, you also have to consider the CompactFlash card's speed, and what transfer technology it supports. Cheap CF cards do not support the faster DMA transfer and you'll be stuck with PIO. (At the time of writing) CF Cards go up to 133x, which is 20MBps, and will be the limiting factor if you get one that supports DMA.

The CF 6.0 Spec includes data rates up to 167MBps via IDE DMA Mode 6 ports. This may not apply to your question, but is included for completeness.

share|improve this answer
Can you expand your answer a little, maybe back it up with links, et cetera? That would be great – it currently is marked as a "low quality" post. – slhck Jul 18 '12 at 18:24
Much better @ChrisS – Ivo Flipse Jul 18 '12 at 19:25
+1 best reaction to a review comment I've seen these days, and quite detailed too! – Tom Wijsman Jul 18 '12 at 19:26

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.