On Fri, 5 Feb 1999, Mark Hahn wrote:
> > Why must the IDE cable be < 18" I have a 27" cable and have had no
> > problems thus far...(my tower case is too large to have anything less then
> > 27" cables)
>
> 18" is what the spec states. the main issue is propogation delay:
> the spec models the cable as a transmission like with speed .6 c,
> and expects 2.5ns delay. your cable is probably pushing 4ns,
> which means that you should DEFINITELY either use lower-speed modes
> (where timing is not as critical), or go for a UDMA mode, where every
> transfer is checksummed.
Bless you, Mark. What amazingly useful information! I'll bet there
aren't ten vendors in the entire country that have ever heard this and
are blindly building IDE systems with long cables.
Boy, live and learn, I always say...:-)
rgb
Robert G. Brown http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567 Fax: 919-660-2525 email:[EMAIL PROTECTED]
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