On Wed, 22 Mar 2006, Dave Dunfield wrote:
TO ALL:
Does anyone else have an Adaptec 1522A controller that you can try with my
latest version of ImageDisk to see if you can read/write single-density disks?
I don't have this controller to test with, and I would like to confirm that the
problem is generic and not related to the one particular unit in question.
I did some tests of several FDC chips found on different Multi-I/O boards
and motherboards some time ago, here are my results:
These work fine with single-density (reading and writing):
M5105 (Acer)
WD37C65 (Western Digital)
i82072 (Intel)
DP8473 (National Semiconductors)
SMC Super I/O chip found on many motherboards
(e.g. old Intel or Asus boards)
These won't work at all: Winbond W83757, Intel i82077 and other modern
crap.
There's one unusual constellation that not many FDCs support:
MFM with 128 bytes/sector. I have a Robotron A5120 computer (ex-GDR) that
uses 26 sectors with 128 bytes/sector and *MFM* on a 5.25" 96tpi
double-density diskette, so the layout is exactly the same as with
8" drives, but only half the data rate (250 kbits/sec.)
My tests showed that the M5105 and DP8473 can read *and* write such
diskettes, the other FDCs can't even reliably read them (e.g. they only
read around 80 instead of 128 bytes etc.)
Another thing to take care of:
Some FDCs don't work reliably in FM mode at a bit rate of 150 kbits/sec.
So in order to write single density minifloppies (48 or 96 tpi) you
should either use a drive with dual speed (300 and 360 rpm selected via
the density select input pin 2) or use a drive that is fixed to 300 rpm;
in both cases use a data rate of 125 kbits/sec.
(I have a CP/M system that uses an Intel 8271 FDC at 125 kbits/sec, this
is a FM only chip)
Hope that helps in finding usable I/O boards and FDCs.
I have a multi-media PC (a PC that handles multiple medias, what else?)
with 3.5" and 5.25" HD at the primary onboard FDC, and a 5.25" 96tpi
DD(300rpm ) and 8" drive connected to an ISA Multi-I/O board with DP8473
set to the secondary address. This handles most of the diskette formats
I have.
Christian