🚀 go-pugleaf

In article <14952@cbmvax.commodore.com> ken@cbmvax.commodore.com (Ken Farinsky - CATS) writes:
>In article <34582@cup.portal.com> Donald_B_Phillips@cup.portal.com writes:
>>Does anybody know what the maximum block number is for a hard disk?  I've got
>>a Maxtor 8760S drive (which I finally got to work with the A2090 controller)
>>and can only address about 1250 cylinders out of a possible 1632.  The drive
>>has 15 heads & 54 sectors per track, which is what I'm using in the mountlist.
>>
>>The drive is a SCSI device.  Am I possibly hitting some other limit for
>>sectors/track or cyliders?
>
>I believe that the 2090 is limited in the number of heads it can deal
>with (I think 7 or 8 max.)  What you should do is cut the number of heads
>to something like 5, increase the sectors per track to come up with
>the correct total.  SCSI only cares about the total number of sectors.
>You could tell it 1 head and it would be ok, only a sector number is
>passed to the drive for access.

	Sorry, ken, you have it a bit backwards.  The ST506 portion of the
A2090 cannot deal with more than 8 heads.  The scsi side doesn't care about
heads.  Both, however, care about the number of sectors/track - 127 or 128
is the limit, due some buffer and math issues.  For a drive like that, using
1 head and many sectors will not work properly.  I suspect the drive is big
enough to run into a math limitation in it's device addressing..

	BTW, the 8 head thing can be fixed by modifying the Z80 EPROM code
to use it for heads instead of (I think) reduced write current.  Dale Luck
has info on how to do this, I think.

-- 
Randell Jesup, Keeper of AmigaDos, Commodore Engineering.
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Common phrase heard at Amiga Devcon '89: "It's in there!"