Replacing drives on classic systems was Wild-hair floppy drive question

Randy McLaughlin cctalk at
Tue Jun 14 13:04:11 CDT 2005

From: "Dwight K. Elvey" <dwight.elvey at>
Sent: Tuesday, June 14, 2005 11:32 AM

> >From: "Randy McLaughlin" <cctalk at>
>>When replacing drives in classic systems there are some things to keep in
>>Newer drives are mainly compatible but not 100%.
> Hi
> Termination is another thing that many miss. Too much
> is often just as bad as too little. Many newer drives
> are not clear how to disable the termination or enable
> it.
> Dwight

This issue only affects 3.5" drives which no longer use the same termination 
(but is compatible with).

I'll have to look up the technical details (hopefully someone will speak up 
first) but basically the floppy drivers on PC's have gone from open 
collector TTL to CMOS changing the characteristics of the line drivers.

I am not sure about details like maximum cable length etc. but 3.5" drives 
can be mixed with TTL driven drives and termination then becomes optional. 
The 3.5" drivers pull up the lines enough to make termination unnecessary, 
of course you still don't want two TTL type drives terminated on the same 


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