[Coco] 720k sssd

Gene Heskett gene.heskett at verizon.net
Sat Feb 27 16:32:27 EST 2010


On Saturday 27 February 2010, Rick Ross wrote:
>Does anyone off the top of their head know the dmode for a 3.5 in to make
> it sssd?

If you mean a std 35 track SSDD?  I don't believe, and I have never tested a  
3.5" disk formatted to SD on the coco's controllers.  That would involve 
either slowing the FDC chps baud rate to 125 kilobaud, or speeding the drive 
spindle up to 600 rpm.  Else it would only do 9, 256 byte sectors per track.  
That would give a disk capacity of only 80,640 bytes.

Another item I've found is that the data decoders in most 3.5" drives cannot 
slow to that data rate.  They can work at rates near 250kb for DD disks, near 
500kb for HD disks, and 1 megacycle for QD (2.88 megabyte) disks for some, 
now rare drives.

That would be sid=01 cyl=23, and just for completeness, typ=21, which ID's it 
as a 3.5" disk.  It (typ) doesn't matter at boot time if you are booting from 
a 3.5" drive AFAIK.

>Thanks in advance
>
>Rick
>
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>


-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)

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