ATA/66 cable question

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Mike Meyers writes (A+ Cert Exam Guide 6th ed. p.314 para 1)

"If you plug an ATA/66 drive into an older controller it will work - just not in ATA/66 mode. The only risky action is to use an ATA/66 controller and hard drive with non-ATA/66 cable. Doing so will almost certainly cause nasty data losses."

Is this true? Other sources imply 40 wire cable is safe, it just reverts to ATA/33 speed.

e.g. http://www.hardwaresecrets.com/article/45/6
"If you have a ATA-66 hard disk or above you have to use an 80-wire flat cable, or your hard disk will achieve only a maximum 33 MB/s transfer rate."
and many other places.

I've seen this come up on A+ practice questions so I'd like to get it straight.

Phil.

 

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Phil,

I believe this is correct. The extra wires are earth wires which help prevent data loss.

This is purely theory - it would be an *old* machine with a 40 IDE cable.

Boyce

Cue Harry for a *decent* answer!

 

Boyce - which is correct - the first (Meyers) quote or the second?

Further to original post - Meyers contradicts himself in a review question at the end of the chapter. Question is "John purchased an ATA/66 drive for his ATA/66 capable system. However he forgot to get the special 80-wire cable. If he installs a 40-pin EIDE cable, what will happen?". Answer is "The drive will work but will not run at ATA/66 speed." Meyers comments "ATA/66 drives work fine with a 40-pin cable - they just won't run at ATA/66 speed". No "nasty data losses" then???

Even more confused...

 

Phil,

I thought it was correct to say the extra wires are needed to help prevent data loss.

No mention is made of this on the Totalsem website here.

 

Correct me if I am wrong guys, but I think that the drive should work in a non compatible ATA/66 controller but there is a possibility to loss of data that might occur. Not to mention that the hard drive will work at the slower speed.

Now is the data loss going to occur constantly I dont know it might.

tallphil here a little reference I used to read up on it, maybe it will help you. http://en.wikipedia.org/wiki/AT_Attachment

 

The extra wires in an 80 pin cable are extra ground wires only.

The drive will automatically operate at the max speed for a drive with a 40 pin cable ie ATA33.

Data loss would only occur at ATA66 or above if you could get this speed with a 40 pin cable. Since the controller / drive will auto select the max speeed for any given cable no data loss will occur.

I retrofit for repair many ATA100 drives to ATA33 controllers with no problem. You may need to select a drive with a cap limiter for the older bios compability issues but thats another story.

 

<grin>

In theory all that should happen is that the controller/drive reduces to legacy speeds.

However - there was a period in the changeover where the drives weren't quite right, and running like this could cause corruption.

What the 'correct to A+' answer is I don't know.

Harry.

 

Thanks very much for the replies. I think that clears it up.

It's rather odd that Mr Meyers holds two opposite views in one chapter though. Wonder if he really writes these books or has a team of minions...

Phil.

 

Have you contacted him to clarify the answer to the question? I'm sure he's very approachable.