[Ham-Computers] RE: 5-1/4 FDD Question

[WA5CAB at cs.com]

OK.  Thanks.  I once knew all of that but hadn't thought about it in years.  
Except that the failure of that system board to recognize what a few hours 
earlier I knew had been a working drive made me wonder whether system board 
vendors had just quietly dropped support for the 5-1/4.

But after reading that, it occurred to me that I do have one machine that 
still has a 360K drive.  It's a Compaq Portable I.  But it also hasn't been lit 
off since the early 90's.  :-)  I also have a Portable II, the rare at the time 
(and never put into production) 3 drive bay machine.  But it only has the 
"modern" 3.5 inch FDD.  :-)

In a message dated 5/19/2008 6:30:12 PM Central Daylight Time, 
aaron.hsu at nbcuni.com writes: 
> Short answer is, yes, if your motherboard has a floppy drive controller 
> (and connector), it should recognize a standard PC-style 5.25" floppy drive (360
> K or 1.2M).
> 
> Most all x86 motherboards with a floppy controller should still be able to 
> recognize the IBM standard 5.25" and 3.5" drives (360K, 1.2M, 720K, 1.44M, 
> 2.88M).  However, most people have probably forgotten that the drive needs to be 
> jumpered properly, just like hard drives (SATA an exception).
> 
> Floppy drive cables usually have two connectors with a "twist" in the cable 
> between the drive "0" and drive "1" connectors.  The twist was to make it 
> simple to install the drives - set the both drives to ID "1" and the twist 
> "reversed" this selection.  So, if you set the drive ID to "1" and attach the 
> drive to the "end" connector on a 2-drive cable, then the system "sees" the end 
> drive as "0" - therefore, it's the "A:" drive.  So, if your floppy drive cable 
> has the twist, make sure the drive is set to ID "1".  
> 
> Word of warning...if you use a 1.2M floppy drive and *write* the the 360K 
> disk, you may not be able to read that disk in a 360K drive anymore.  It's a 
> physical thing...the R/W heads on a 1.2M drive are 1/2 as wide as a 360K drive, 
> so you're not writing data across the "full" width of the track (360K drive 
> has 48 tracks per inch, 1.2M drive has 96 tracks per inch).  So, when you try 
> to read the data in a 360K drive, it's R/W head picks-up the data written by 
> the 1.2M drive along with whatever data was on the rest of the track.  These 
> two combined usually add up to garbage and the 360K drive responds with a 
> sector read error.  By the way, same problem occurs with 100MB/250MB/750MB ZIP 
> disks and drives.
> 

Robert Downs - Houston
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