17 May
2023
17 May
'23
8:34 p.m.
Please forgive my typo, you are correct it was 5 1/4 inch not 5 1/2 inch.
The read track function works somewhat on the WD1791 if it is able to
sync up. Sometimes you need to read a track several times to get it to
read correctly. It also starts reading at the first address mark it
finds and ignores the index pulse.
The WD1971 used a 1MHz clock for single and double density 5 1/4" disks
and a 2MHz clock for single and double density 8" disks. This gave the
8" disk double the data density of a 5 1/4" disk.
When testing my formatting code on the Gimix controller I used the read
track to verify that i was writing the sectors correctly.
On 5/17/2023 3:13 PM, Fred Cisin via cctalk wrote:
On Wed, 17 May 2023, Mike Katz wrote:
If you have access to a Gimix SS-50 6809 or 6800
system, Gimix used
the WD1791 in their double density disk controller. That controller
can do single and double density 5 1/2" and 8" disks (250KHz, 500KHz
& 1MHz data rates).
Some NEC 765 controllers, including the original 5150/5160 are
hard-wried to not be able to do single density, and they have a
limited range of data transfer rates.
Other than that, 5170 style controllers can do double density 5.25"
(sorry, there is no 5 1/2" disk), and 8".
The ones that support single density (check Dave Dunfield's site) can
do single and double density 5.25" and 8".
The 1MHz data transfer rate is needed for the 2.8M 3.5".
So, those capabilities are same as many NEC 765 PCs.
But, the WD1791 includes a real TRACK READ! Try that for Amiga!
The NEC 765 design does not have a real TRACK READ; instead, it offers
a multiple sector read.