17 May
2023
17 May
'23
6:05 p.m.
Message: 21
Date: Wed, 17 May 2023 04:56:05 +0100
From: Tony Duell <ard.p850ug1(a)gmail.com>
Subject: [cctalk] Re: ST-251 Data Recovery for Glenside Color Computer
Club (GCCC)
<snip>
As for the target machine having a serial port, one of
the machines I
want to get stuff onto is an Osborne 1A. The serial port on that is
horrible.
<snip>
-tony
For CP/M computers such as the Osborne, you can read and write their diskettes on an
MS-DOS computer with a program like Media Master. KayPro disks are harder, as there are
problems formatting them on an MS-DOS computer.
Bob
17 May
17 May
7:38 p.m.
New subject: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
> As for the target machine having a serial port,
one of the machines I
> want to get stuff onto is an Osborne 1A. The serial port on that is
> horrible.
On Wed, 17 May 2023, Robert Feldman via cctalk wrote:
For CP/M computers such as the Osborne, you can read
and write their
diskettes on an MS-DOS computer with a program like Media Master. KayPro
disks are harder, as there are problems formatting them on an MS-DOS
computer.
The earliest Osbornes were single density with ten 256 byte sectors per
track. I was able to write some code on TRS80 model 1 to read those.
Many PC FDCs, including the IBM 5150/5160, can not do FM/single-density.
Then Osborne came out with a "double density upgrade". The
MFM/Double-density Osborne disks are easy to do with PC, if you are
familiar with INT13h and INT1Eh.
But, my original stock 5150 PC could never read the original/early Osborne
disks.
Single sided Kaypro disks were not hard to do. Nothing special, other
than smaller than ideal inter-sector gaps to squeeze ten 512 byte sectors
per track.
But, the double sided Kaypro disks had an incorrect value in the head
number field of the sector headers of the second side! The WD controller
used in the Kaypro ignored that field, but the NEC FDC insisted on a
match. I tried some double-sided Kaypros, and found that they would work
fine with disks that had the correct value in the head number field. So,
I could format the disks in Kaypro double sided format on the PC, then
copy files to those pseudo Kaypro disks on the Kaypro, and bring themback
to the PC to read.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
8 p.m.
New subject: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
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).
On 5/17/2023 2:38 PM, Fred Cisin via cctalk wrote:
> As for the
target machine having a serial port, one of the machines I
> want to get stuff onto is an Osborne 1A. The serial port on that is
> horrible.
On Wed, 17 May 2023, Robert Feldman via cctalk wrote:
For CP/M computers such as the Osborne, you can
read and write their
diskettes on an MS-DOS computer with a program like Media Master.
KayPro disks are harder, as there are problems formatting them on an
MS-DOS computer.
The earliest Osbornes were single density with ten 256 byte sectors
per track. I was able to write some code on TRS80 model 1 to read those.
Many PC FDCs, including the IBM 5150/5160, can not do FM/single-density.
Then Osborne came out with a "double density upgrade". The
MFM/Double-density Osborne disks are easy to do with PC, if you are
familiar with INT13h and INT1Eh.
But, my original stock 5150 PC could never read the original/early
Osborne disks.
Single sided Kaypro disks were not hard to do. Nothing special, other
than smaller than ideal inter-sector gaps to squeeze ten 512 byte
sectors per track.
But, the double sided Kaypro disks had an incorrect value in the head
number field of the sector headers of the second side! The WD
controller used in the Kaypro ignored that field, but the NEC FDC
insisted on a match. I tried some double-sided Kaypros, and found
that they would work fine with disks that had the correct value in the
head number field. So, I could format the disks in Kaypro double
sided format on the PC, then copy files to those pseudo Kaypro disks
on the Kaypro, and bring themback to the PC to read.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
8:13 p.m.
New subject: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
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.
8:34 p.m.
New subject: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
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.
18 May
18 May
4:06 a.m.
New subject: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Wed, May 17, 2023 at 8:38 PM Fred Cisin via cctalk
<cctalk(a)classiccmp.org> wrote:
The earliest Osbornes were single density with ten 256
byte sectors per
track. I was able to write some code on TRS80 model 1 to read those.
Many PC FDCs, including the IBM 5150/5160, can not do FM/single-density.
Then Osborne came out with a "double density upgrade". The
MFM/Double-density Osborne disks are easy to do with PC, if you are
familiar with INT13h and INT1Eh.
It's odd... The Osborne had a double-density-capable disk controller
chip (WD1793) from the start. The double density board is the
necessary data separator and write precompensation stuff.
I have it in my Osborne, thankfully. I also have the 80 column
'Screenpac' upgrade, which is not relevant here.
-tony
4:44 a.m.
New subject: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
> The earliest Osbornes were single density with ten
256 byte sectors per
> track. I was able to write some code on TRS80 model 1 to read those.
> Many PC FDCs, including the IBM 5150/5160, can not do FM/single-density.
> Then Osborne came out with a "double density upgrade". The
> MFM/Double-density Osborne disks are easy to do with PC, if you are
> familiar with INT13h and INT1Eh.
On Thu, 18 May 2023, Tony Duell wrote:
It's odd... The Osborne had a
double-density-capable disk controller
chip (WD1793) from the start. The double density board is the
necessary data separator and write precompensation stuff.
I have it in my Osborne, thankfully. I also have the 80 column
'Screenpac' upgrade, which is not relevant here.
No, but it sure did make it nicer to use!
Sometime, I should ask Lee Felsenstein about what was going on.
Perhaps, Adam was in a big hurry to get it released, and perhaps the
double density was removed from the specs until the data separator and
write precomp could be ready?
Or, . . . maybe the early design had a 1771?, and then when they
switched to the 1793, they removed the MFM functionality for existing
orders?
But, Adam would NEVER have delayed announcing an upgrade. THAT was his
usual fatal foot-shot.
I was right across the aisle at the Computer Faire when he announced the
machine. We were peddling the Elcompco model 1, which was a TRS80
repackaged in a Halliburton attache case, with added data acquisition
hardware.
On the TRS80, the 1771 had serious problems unless/until you added a data
deparator.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
553
days inactive
554
days old
6 comments
4 participants
participants (4)
-
Fred Cisin -
Mike Katz -
Robert Feldman -
Tony Duell