7 Apr
2003
7 Apr
'03
10:15 a.m.
I picked up an old IBM XT today and it has a 3.5" floppy drive in it (and it
works!) Anybody ever heard of this? The drive has it's own controller card and both it
and the drive appear to be IBM parts. )I haven't pulled everything apart to be sure.)
FWIW the computer also has a FH 5 1/4" floppy drive and a HH 5 1/4" 10 Mb hard
drive with a Seagate logo on the front of it. Anybody know if this is an original XT hard
drive or a replacement drive? It's been so long since I've seen an original XT
with the 10 Mb drive that I don't remember much about it.
Joe
7 Apr
7 Apr
10:43 a.m.
On Mon, 7 Apr 2003, Joe wrote:
I picked up an old IBM XT today and it has a
3.5" floppy drive in it
(and it works!) Anybody ever heard of this?
Presumably, that is a 720K drive (subject to what the extra controller
is). IBM sold internal and external 720Ks for the XT. To do it their
way, you need PC-DOS 3.20 or newer, and need to do a DRIVER.SYS in
CONFIG.SYS. But you could also use a 720K with certain OEM
(NON-IBM) versions of MS-DOS 2.11.
And the PC-JX (not available in U.S.) was available with 720K drives.
The drive has it's own
controller card and both it and the drive appear to be IBM parts. )I
haven't pulled everything apart to be sure.) FWIW the computer also
Do you mean that it is NOT connected to the same controller as the
5.25" drive?
has a FH 5 1/4" floppy drive and a HH 5 1/4"
10 Mb hard drive with a
Seagate logo on the front of it. Anybody know if this is an original
XT hard drive or a replacement drive? It's been so long since I've
seen an original XT with the 10 Mb drive that I don't remember much
about it.
Which model Seagate? It is likely to be an aftermarket drive.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
2:14 p.m.
At 03:41 PM 4/7/03 -0700, you wrote:
I expect that you're right. But it definitely appears to be connected an an IBM
controller card. Interesting tidbit; the controller has BOTH data cables installed on it
even though there's only one hard drive. The cables are stacked one on top of the
other and taped together. I think this is the only time that I've ever seen a
controller that came with two data cables.
FINALLY got the drive out! Two screws on the side (inside side, of course!) had backed
out partially and jammed it up good. The drive is a ST 238R (32Mb) so it's definitely
not an original drive.
Joe
On Mon, 7 Apr 2003, Joe wrote:
My mistake. It IS on the same controller. It didn't look like it till I got it
apart.
I picked up an old IBM XT today and it has a
3.5" floppy drive in it
(and it works!) Anybody ever heard of this?
Presumably, that is a 720K drive (subject to what the extra controller
is). IBM sold internal and external 720Ks for the XT. To do it their
way, you need PC-DOS 3.20 or newer, and need to do a DRIVER.SYS in
CONFIG.SYS. But you could also use a 720K with certain OEM
(NON-IBM) versions of MS-DOS 2.11.
And the PC-JX (not available in U.S.) was available with 720K drives.
The drive has it's own
controller card and both it and the drive appear to be IBM parts. )I
haven't pulled everything apart to be sure.) FWIW the computer also
Do you mean that it is NOT connected to the same controller as the
5.25" drive? has a FH 5 1/4" floppy drive and a HH 5
1/4" 10 Mb hard drive with a
Seagate logo on the front of it. Anybody know if this is an original
XT hard drive or a replacement drive? It's been so long since I've
seen an original XT with the 10 Mb drive that I don't remember much
about it.
Which model Seagate? It is likely to be an aftermarket drive.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
2:28 p.m.
On Mon, 7 Apr 2003, Joe wrote:
I expect that you're right. But it definitely
appears to be
connected an an IBM controller card. Interesting tidbit; the controller
has BOTH data cables installed on it even though there's only one hard
drive. The cables are stacked one on top of the other and taped
together. I think this is the only time that I've ever seen a
controller that came with two data cables.
FWIW, All of the XTs and ATs I've taken apart have had both data cables
installed, and taped together like you said.
Pat
--
Purdue Universtiy ITAP/RCS
Information Technology at Purdue
Research Computing and Storage
http://www-rcd.cc.purdue.edu
3:52 p.m.
On Mon, 7 Apr 2003, Joe wrote:
My mistake. It IS on the same controller. It
didn't look like it till I got it apart.
Is it a 720K? (look for a media sensor in the drive for a quick but not
certain test) If so, then it has no need for any difference in cntroller
or BIOS than a 360K.
>Which model Seagate? It is likely to be an
aftermarket drive.
I expect that you're right. But it definitely
appears to be
connected an an IBM controller card. Interesting tidbit; the
controller has BOTH data cables installed on it even though there's
only one hard drive. The cables are stacked one on top of the other
and taped together. I think this is the only time that I've ever seen
a controller that came with two data cables.
Yeah, IBM always did that (taping the cables together, prefolded to fit
tidily in the case) That tape is prbably pretty thoroughly decayed by
now.
FINALLY got the drive out! Two screws on the side
(inside side, of
course!) had backed out partially and jammed it up good. The drive is
a ST 238R (32Mb) so it's definitely not an original drive.
I think that the R means that it is rated for RLL use.
The original stock IBM hard drive controller came set for 10M, but could
be jumpered (solder jumpers or put in a dipswitch) for IIRC, 5M, 10M, 16M,
26M?
Minor bad news: on the XT (not AT), there were incompatabilities between
different controllers, so the drive needs to be reformatted to switch to a
different brand of controller!
--
Grumpy Ol' Fred cisin(a)xenosoft.com
5:50 p.m.
On Mon, 7 Apr 2003, Joe wrote:
At 03:41 PM 4/7/03 -0700, you wrote:
I expect that you're right. But it definitely appears to be connected an an IBM
controller card. Interesting tidbit; the controller has BOTH data cables installed on it
even though there's only one hard drive. The cables are stacked one on top of the
other and taped together. I think this is the only time that I've ever seen a
controller that came with two data cables.
FINALLY got the drive out! Two screws on the side (inside side,
of course!) had backed out partially and jammed it up good. The
drive is a ST 238R (32Mb) so it's definitely not an original
drive.
Interesting question is whether it is being used as a 21mb MFM
drive or as a 33mb RLL. My guess would be 21mb.
- don
On Mon, 7 Apr 2003, Joe wrote:
My mistake. It IS on the same controller. It didn't look like it till I got it
apart.
I picked up an old IBM XT today and it has a
3.5" floppy drive in it
(and it works!) Anybody ever heard of this?
Presumably, that is a 720K drive (subject to what the extra controller
is). IBM sold internal and external 720Ks for the XT. To do it their
way, you need PC-DOS 3.20 or newer, and need to do a DRIVER.SYS in
CONFIG.SYS. But you could also use a 720K with certain OEM
(NON-IBM) versions of MS-DOS 2.11.
And the PC-JX (not available in U.S.) was available with 720K drives.
The drive has it's own
controller card and both it and the drive appear to be IBM parts. )I
haven't pulled everything apart to be sure.) FWIW the computer also
Do you mean that it is NOT connected to the same controller as the
5.25" drive? has a FH 5 1/4" floppy drive and a HH 5
1/4" 10 Mb hard drive with a
Seagate logo on the front of it. Anybody know if this is an original
XT hard drive or a replacement drive? It's been so long since I've
seen an original XT with the 10 Mb drive that I don't remember much
about it.
Which model Seagate? It is likely to be an aftermarket drive.
Joe
>
>--
>Grumpy Ol' Fred cisin(a)xenosoft.com
3:13 a.m.
New subject: MFM vs RLL or ST-225 vs ST-238R (was Re: 3.5" floppy drive in IBM XT?)
--- Joe <rigdonj(a)cfl.rr.com> wrote:
At 10:47 PM 4/7/03 -0700, Don wrote:
Does that mean that you confirmed that your controller is an RLL
controller? There's no substantial difference between an ST-238R
and an ST-225 except a) the label, and b) some manufacturing confidence
that a tighter encoding scheme will not drop bits.
The data cable holds analog signals. This is significantly different
than an IDE drive (whose cable is all digital). The density of storage
is entirely dependent on the nature of the controller. The quality
of retention is dependent on the nature of the drive.
People did attempt to stick an ST-225 on an RLL controller. Results
were mixed. It was a "cheap" way to increase storage 50%, but if
your drive had some weak spots, you would develop lots of data errors.
Others chose to put ST-238Rs on MFM controllers. Results there were
much better. You only got 21.4MB of storage (marketing MB, AFAIK),
but you weren't taxing the surface as much as Seagate said you could.
So, yes, your sources are correct - the ST-238R *does* do 32MB, but
only when attached to an RLL controller (which you might very well have).
-ethan
P.S. - there were other arrangements than 614 x 4 x 17 when ST-506/ST-412
drives were used in non-PeeCee applications. One that immediately comes
to mind is the Tandon drive (TM602S or TM603S) used in the Commodore
D9060 and D9090 IEEE-488 hard drives. Due to the nature of Commodore
"DOS" and its floppy origins, they chose not to change the block size
of 256 bytes per block. Its internal OMTI controller did tracks of
32 sectors of 256 bytes for a total of 8192 bytes per track, not
8704 (17 x 512). Yes, to keep it on topic, the ST-225 will work in a
D9060, but will only use the first 154 tracks).
(see http://www.softwolves.pp.se/misc/arkiv/cbm-hackers/2/2264.html ,
among other things you can find googling for D9090)
Interesting question is whether it is being used as a 21mb MFM
drive or as a 33mb RLL. My guess would be 21mb.
It's an RLL drive and is 32 Mb according to my sources.
9:23 a.m.
New subject: MFM vs RLL or ST-225 vs ST-238R (was Re: 3.5" floppy drive in IBM XT?)
At 08:10 AM 4/8/03 -0700, you wrote:
--- Joe <rigdonj(a)cfl.rr.com> wrote:
No, my controller is an original IBM 10 Mb MFM HD controller. It's only using 10 Mb
of the drive.
Joe
At 10:47 PM 4/7/03 -0700, Don wrote:
Does that mean that you confirmed that your controller is an RLL
controller?
Interesting question is whether it is being used as a 21mb MFM
drive or as a 33mb RLL. My guess would be 21mb.
It's an RLL drive and is 32 Mb according to my sources. 
10:19 a.m.
New subject: MFM vs RLL or ST-225 vs ST-238R (was Re: 3.5" floppy drive in
--- Joe <rigdonj(a)cfl.rr.com> wrote:
Actually, all the signals on the data cable are digital. The Read/Write
data signals are differential pairs of similar-to-TTL level signals,
normally using a 26LS31 driver and 26LS32 receiver.
But in a sense they're analogue in _time_. In write mode, the drive
writes a flux transition to the disk for every pulse on the write data
line. In read mode, the drive sends a pulse on the read data line for
every flux transition on the disk. There are some restrictions on
allowable frequencies of transisitions, of course.
Therefore it's up to the controller to handle the raw data from the disk,
to sort it out into sectors, check the sector headers and checksums, and
so on. And when writing, the controller has to pack the user's data into
sectors, add the correct headers, etc. The choice of encoding scheme
(FM/MFM/RLL) is up to the controller.
RLL drives should really be called RLL _capable_ drives. They are capable
of handling the somewhat tighter timing requirements of the RLL encoding
scheme. They'll work fine with MFM encoding too (just as double-denisty
-- MFM -- floppy disks will work on a single density -- FM -- controller).
-tony
At 10:47 PM 4/7/03 -0700, Don wrote:
Does that mean that you confirmed that your controller is an RLL
controller? There's no substantial difference between an ST-238R
and an ST-225 except a) the label, and b) some manufacturing confidence
that a tighter encoding scheme will not drop bits.
The data cable holds analog signals. This is significantly different
Interesting question is whether it is being used as a 21mb MFM
drive or as a 33mb RLL. My guess would be 21mb.
It's an RLL drive and is 32 Mb according to my sources.
5:32 a.m.
>Interesting question is whether it is being used
as a 21mb MFM
>drive or as a 33mb RLL. My guess would be 21mb.
On Tue, 8 Apr 2003, Joe
wrote:
It's an RLL drive and is 32 Mb according to
my sources.
But what controller is it connected to?
The IBM controller (full length, made by Xebec) was MFM. ONLY.
When connected to an MFM controller, the drive will only be usable for 2/3
of its rated RLL capacity, giving you a very good 20M drive.
MFM and RLL gave two different recording encodings on what was otherwise
an identical drive. But many/most? MFM drives could not reliably handle
the higher "density" of RLL. Drives that were sold as RLL could.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
6:21 a.m.
On Tue, 8 Apr 2003, Joe wrote:
At 10:47 PM 4/7/03 -0700, Don wrote:
My curiousity was really as to the controller and whether it was
RLL or MFM, Joe.
- don
Interesting question is whether it is being used as a 21mb MFM
drive or as a 33mb RLL. My guess would be 21mb.
It's an RLL drive and is 32 Mb according to my sources.
9:23 a.m.
Don,
The controller is full length and has XEBEC chips and a Z-80 CPU. I'm sure that
it's MFM. It's marked IBM and next to that is a paper sticker that says #1501492.
Also marked IBM 6135984 in copper foil. My diagnostic tool shows four settings in the ROM,
the 10Mb drive is third setting. I didn't look at the capacity of the other settings.
It's running this drive as a 10 Mb MFM drive but the drive is rated as a 32Mb RLL
capable drive.
Joe
At 11:19 AM 4/8/03 -0700, you wrote:
On Tue, 8 Apr 2003, Joe wrote:
At 10:47 PM 4/7/03 -0700, Don wrote:
My curiousity was really as to the controller and whether it was
RLL or MFM, Joe.
- don
Interesting question is whether it is being used as a 21mb MFM
drive or as a 33mb RLL. My guess would be 21mb.
It's an RLL drive and is 32 Mb according to my sources.
9:52 a.m.
On Tue, 8 Apr 2003, Joe wrote:
The controller is full length and has XEBEC chips
and a Z-80 CPU.
I'm sure that it's MFM. It's marked IBM and next to that is a paper
sticker that says #1501492. Also marked IBM 6135984 in copper foil. My
diagnostic tool shows four settings in the ROM, the 10Mb drive is
third setting. I didn't look at the capacity of the other settings.
It's running this drive as a 10 Mb MFM drive but the drive is rated as
a 32Mb RLL capable drive.
my controller is an original IBM 10 Mb MFM HD
controller. It's only
using 10 Mb of the drive.
Near the middle of the board are 8 solder pads. By jumpering those (they
are the right size for a 4 position dip switch), you can get the
controller to use the other setting that are in its ROM. The 4 positions
are 2 for each drive, resulting in 4 possible combinations for each
drive. 10M, the default, is both switches open.
OR, there are software ways tio override the controller -
check with Steve Thatcher.
1:13 p.m.
Thanks for the info but I don't see the pads that you're talking about. Near
the center of the card are pads for a 14 pin DIP with nothing strapped. It's unlabeled
but is located between ICs 8D and 10D. Right next to the bracket on the very end of the
card is a place for an 8 pin DIP. It has the package outline painted on the board. But it
has two rows on header pins installed instead of a DIP package. (The rows are .4"
apart.) One row of pins is marked S1 and the other is marked 1, 2, 3, 4. There's
nothing jumpered on it either but I suspect that it's used to select the drive sizes.
Joe
At 02:49 PM 4/8/03 -0700, you wrote:
On Tue, 8 Apr 2003, Joe wrote:
The controller is full length and has XEBEC
chips and a Z-80 CPU.
I'm sure that it's MFM. It's marked IBM and next to that is a paper
sticker that says #1501492. Also marked IBM 6135984 in copper foil. My
diagnostic tool shows four settings in the ROM, the 10Mb drive is
third setting. I didn't look at the capacity of the other settings.
It's running this drive as a 10 Mb MFM drive but the drive is rated as
a 32Mb RLL capable drive.
my controller is an original IBM 10 Mb MFM HD
controller. It's only
using 10 Mb of the drive.
Near the middle of the board are 8 solder pads. By jumpering those (they
are the right size for a 4 position dip switch), you can get the
controller to use the other setting that are in its ROM. The 4 positions
are 2 for each drive, resulting in 4 possible combinations for each
drive. 10M, the default, is both switches open.
OR, there are software ways tio override the controller -
check with Steve Thatcher. 
2:16 p.m.
On Tue, 8 Apr 2003, Joe wrote:
At 02:49 PM 4/8/03 -0700, you wrote:
The 8 pin dip outline near the bracket is what you are looking for. I've
seen WD boards with empty pads, a 4 position dip switch, an empty socket,
and a socket with a punch-type shunt installed. I used to just plug a
standard 4 position dip switch into the header/socket to make selecting
the various drive types much simpler.
-Toth
Near the middle of the board are 8 solder pads.
By jumpering those
(they are the right size for a 4 position dip switch), you can get the
controller to use the other setting that are in its ROM. The 4
positions are 2 for each drive, resulting in 4 possible combinations
for each drive. 10M, the default, is both switches open.
Thanks for the info but I don't see the pads that you're talking about.
Near the center of the card are pads for a 14 pin DIP with nothing
strapped. It's unlabeled but is located between ICs 8D and 10D. Right
next to the bracket on the very end of the card is a place for an 8 pin
DIP. It has the package outline painted on the board. But it has two
rows on header pins installed instead of a DIP package. (The rows are
.4" apart.) One row of pins is marked S1 and the other is marked 1, 2,
3, 4. There's nothing jumpered on it either but I suspect that it's used
to select the drive sizes.
10:19 a.m.
At 10:47 PM 4/7/03 -0700, Don wrote:
All that means is the drive is capable of handling RLL encoding
(basically, it can correctly reproduce pulses at half-multiples of the
MFM spacing (although they won't ever be closer together than
the MFM encoder would produce). Such a drive will, of course, work
correctly with an MFM controller, but will have a lower capacity when so
used (in this case 21 Mbytes).
Remember that with the ST506/ST412 interface, it's the _controller_, not
the drive that handles the data encoding/decoding. The 'data cable'
carries the raw data stream to/from the disk.
-tony
Interesting question is whether it is being used as a 21mb MFM
drive or as a 33mb RLL. My guess would be 21mb.
It's an RLL drive and is 32 Mb according to my sources. 
7 Apr
7 Apr
11:02 a.m.
Joe,
This is quite possible... Provided you have DOS 3.3+ and a controller with its own
BIOS extensions. I have an XT machine (actually it's an original PC) that works much
the same way, although the drive is unusable as
I'm currently using DOS 3.21. As far as the hard drive goes, the original XT hard
drive was a FH job with an IBM logo on the front
of it.
John
+------------------------------------------------+--------------------------------+
| John P. Willis, MCP, SBI, NASA-STD-8739.5 | Coherent Logic Development |
| Chief Executive Officer | "Multiplatform Solutions |
| Coherent Logic Development | for a Multiplatform World" |
+------------------------------------------------+--------------------------------+
| web: http://www.coherent-logic.com/ |
| e-mail: ceo(a)coherent-logic.com |
+---------------------------------------------------------------------------------+
----- Original Message -----
From: "Joe" <rigdonj(a)cfl.rr.com>
To: <cctech(a)classiccmp.org>
Sent: Monday, April 07, 2003 6:12 PM
Subject: 3.5" floppy drive in IBM XT?
I picked up an old IBM XT today and it has a
3.5" floppy drive in it (and it works!) Anybody ever heard of this? The drive has
it's own controller card and both it and the drive appear to be IBM parts. )I
haven't pulled everything apart to be sure.) FWIW the
computer also has a FH 5 1/4" floppy drive and a HH 5 1/4" 10 Mb hard drive with
a Seagate logo on the front of it. Anybody know if
this is an original XT hard drive or a replacement drive? It's been so long since
I've seen an original XT with the 10 Mb drive that
I don't remember much about it.
Joe
11:17 a.m.
On Mon, 7 Apr 2003, John Willis wrote:
Joe, This is quite possible... Provided you have DOS
3.3+ and a
controller with its own BIOS extensions. I have an XT machine
(actually it's an original PC) that works much the same way, although
the drive is unusable as I'm currently using DOS 3.21. As far as the
hard drive goes, the original XT hard drive was a FH job with an IBM
logo on the front of it.
PC-DOS 3.30, BIOS extensions, and a different controller card are
needed for a 1.4M drive, but NOT for 720K.
720K uses same BIOS, same controller as 360K. The only difference
is how many tracks it has. PC-DOS 3.20 has full support for 720K
drives in all models.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
4:44 p.m.
Joe,
Wow, major flashbacks!!! I remember installing my 1st 3.5" into an AT,
not XT but I do recall there was a big routine that we had to go through to
install a bunch of drivers and such to allow the system to recognize and use
the 3.5" disk drive.
Curt
----- Original Message -----
From: "Joe" <rigdonj(a)cfl.rr.com>
To: <cctech(a)classiccmp.org>
Sent: Monday, April 07, 2003 6:12 PM
Subject: 3.5" floppy drive in IBM XT?
I picked up an old IBM XT today and it has a
3.5" floppy drive in it
(and it works!) Anybody ever heard of this? The drive
has it's own
controller card and both it and the drive appear to be IBM parts. )I haven't
pulled everything apart to be sure.) FWIW the computer also has a FH 5 1/4"
floppy drive and a HH 5 1/4" 10 Mb hard drive with a Seagate logo on the
front of it. Anybody know if this is an original XT hard drive or a
replacement drive? It's been so long since I've seen an original XT with the
10 Mb drive that I don't remember much about it.
Joe
7929
days inactive
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19 comments
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