power connection for 8" drive -- tandon tm848-01

From: Jim Battle <frustum_at_pacbell.net>
Date: Thu Nov 20 10:57:33 2003

Al Kossow wrote:

>>I intend to connect to a catweasel card for the
>>purpose of getting the bits off of a lot of old PT-DOS disks
>
>
> Aren't SOLOS discs hard-sectored?
>
> The 848 user's manual is at www.bitsavers.org/pdf/tandon
>

yes -- it has a very strange scheme. it is a 32 sector hard sectored
disk, but it isn't used that way. it has variable sized sectors so that
  the inter-sector gap can be used to hold data too. first off, the
disk controller ignores every other sector, so effectively there are 16
possible 256 byte sectors. the OS decides allocation, and files declare
  what sector size they want and the OS allocates things to make it
work. you can ask for a 256 byte sector, but you only get 16 of those
on a track. offhand, I don't recall how much bonus data you get by
using the gap, but it is something like 25-30% extra. at most you can
ask for 13 sector sized blocks, but you get 16*256B of data in that space.

The catweasel, as I understand it, can deal with this, although I'll
have to write the software to decode it.
Received on Thu Nov 20 2003 - 10:57:33 GMT