[Coco] Re: 8" drive to 5.25" replacement?

[Gene Heskett]

On Wednesday 03 December 2003 09:49, Theodore A. Evans wrote:
>On 12/03/03, Roger Taylor wrote:
>> Someone wrote me about a worn out 8" drive on a machine they use
>> and wanted to emulate it by connecting the cable to their PC... :)
>>
>> I told them it might be best to try to replace the drive with an
>> older 5.25" drive that can do single-density mode. What I wanted
>> to ask you guys is if the cables are compatible between 8" and
>> 5.25" drives.
>
>It is my understanding that the cabling is not a difficult issue
>though the connectors are different.  The big issue that comes to
> mind if they are trying to replace a single density 8" floppy drive
> is that these drives spin at the same speed as a 5-1/4" in high
> density mode (500 rpm) and use double the data rate of a 5-1/4"
> floppy., though of course they use FM modulation for single density
> and MFM for double density.  Basically an 8" DD floppy drive looks
> just like a 5-1/4" HD floppy drive with only 77 tracks.

No floppy, 8 inch, 5.25 inch, or 3.5 inch, was ever spun at 500 rpm.
They either spun at 360 for the 8 inchers, or 300/360 for the 5.25 
inchers, and 300/150 for the 3.5 inchers.  And the only place they 
ever ran a 3.5 incher at 150 rpm was in the amiga hi-density, 1.76 
meg format.  It ran so slow you could see the motor cogging, and if 
it weren't for the fact that the disk is pinned to the spindle, 
making the playback cogging match the recorded cogging, it would 
never have worked at all due to the cogging induced data rate 
wibbles.

But lemme tell you that the 150 format is a ticklish pickle, thats 
awfully slow under the read heads and the signal coming back from the 
disk is very, very weak.  I've looked at it on a scope and marveled 
that the data decoder could find good data in all those timing 
wobbles.

-- 
Cheers, Gene
AMD K6-III at 500mhz 320M
Athlon1600XP at 1400mhz  512M
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Copyright 2003 by Maurice Eugene Heskett, all rights reserved.