96TPI

These formats are double density 96TPI, what has sometimes been called "quad" 
density. They can usually be done with a 1.2M drive, however, for best 
reliability, use a "720K 5.25 inch" drive. 

# Visual 1050 - SSDD 96 tpi 5.25"

"VIS400":
 SS QD sect=10

http://fdutils.linux.lu/Fdutils_toc.html

Most of the following has been provided by Allison on the
comp.os.cpm newgsroup.

The winchester port is not quite as it requires an external
adaptor that get you you SCSI to an ADATEK or other SCSI bridge to MFM
disk.

It uses a seperate monitor MGAish, and keyboard (non pc compatible).
The two floppies are single sided 96tpi teac fd55-e drives so it 
does/can do RX50 formats and a few others.  It's circa 1984 and a good 
example of how a 4mhz z80 cpm box can be pushed.

The graphics is done by a seperate 6502 so the z80 is not loaded
by that task and ther is 128k ram for the z80 with mmu.  This is
not the usual Z80 cpm machine.  It was sold with CPM-3 on it.

This was a bank-switched memory system because the Z-80 wouldn't see above 48K. 
The 6502 graphics processing section had 32K

The disk interface is z80 bus at the back of the 1050.  There is a
sidecar box that contains the following, z80 to SASI,  Xybec SASI/SCSI
to MFM 5.25" hard disk, power supplies for the whole mess and of
course a drive like tandon T105.  Mine have 10mb ST412. 

> So I guess the spare IDE drive I have lying around won't plug into that
> port? :)

Not directly.  Though it would be fairly trivial to do 1050bus to IDE.

FYI: for those unknowing; the VISUAL1050 hard disk port is really
the following signals A0->A3, IORD/, IOWR/, reset/, W-sel/, ext-INT/,
EXT-wait/,  D0->D7, and grounds.

the bus to SASI conversion is on a small 4x6" card in the drive and
that goes to a xybex SASI/SCSI bridge to MFM drive.

Key items to acknowledge, the V1050 is more sophisticated than
many CP/M machines.    It has a RTC, complex interrupt structure and
extendable IO for SASI/SCSI interface for a S1410 SASI to MFM bridge
board for hard disk and a intelligent coms port.  The 6502 uses a 6845
CTRC and communicates with the Z80 via 8255 PPI with additional
doorbell interrupt both ways.   IO is interrupt driven for the Z80.
There is also the memory management for the 128K ram and an optional
128K ram for 256k total.  Memory management also deals with 8K boot
rom at 0000h (startup).