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View Full Version : Looking for links to info, parts surplus for Seagate ST-225



rcooke
September 8th, 2015, 08:38 AM
I repair computers and a client brought me this beast!

Brought back fond A][+ memories.... But its out of some industrial machine.

Did some clever company put an MFM controller into a USB dongle yet?

Or maybe an Arduino or Raspberry pi project to talk to one?

Or other?

This machine is not "working" which could mean its just a bad p/s - I'll check that.

But I would like some way to copy data to/from this type of drive.


Thanks in advance!
Richard Cooke

NeXT
September 8th, 2015, 08:59 AM
Ah yes, the ST-225. Seagate's bulletproof MFM hard drive.
There are a handful of MFM drive emulators on the market but none of them are really affordable. I tend to stick to MFM drives so long as they pas a low-level format because it they made it this far, they won't be dropping dead tomorrow.

Unfortunately in the early days of hard disk controllers there was no easy way to move a drive from one machine to another and it would magically work. The controller had to come with it and occasionally you had to know what the CHS parameters were in the process. IF you did not do this you would ultimately be unable to read the disk because the new controller would have no idea what the old controller's preference of geometry was (interleave, track gaps, etc)

Stone
September 8th, 2015, 09:17 AM
Did some clever company put an MFM controller into a USB dongle yet?Since nearly every company that made MFM controllers used a different protocol to LLF the drive this 'dongle' you are dreaming about would need to encompass a multitude of protocols in order to cover most of the necessary bases. :-)

SomeGuy
September 8th, 2015, 09:42 AM
I repair computers and a client brought me this beast!
Well, you've come to the right place. There are lots of people here who can probably help.

Due to all of the different low-level formats used on these drives, there is no way to just plug them in to a common adapter and read them.

Exactly what kind of computer are we talking about here? An IBM PC or clone?

Since you say it is "industrial" I am guessing it has special hardware in it that probably can not be moved to a different machine.

You will need to use the hard drive controller provided with the drive to read it (or one of an identical model). You may be able to insert the hard drive controller in to a slightly newer machine (386, 486, Pentium 1) as long as it has an ISA slot.

Or, if you can get this machine running, you can usually attach a normal 1.44mb drive to PC style floppy controller and use it at least as a 720K 3.5" drive.

Once you have the data read off, you might consider replacing the hard drive with an XT-CF or XT-IDE card

cdbachmann
September 8th, 2015, 09:44 AM
Or maybe an Arduino or Raspberry pi project to talk to one?

Or other?


Richard,

There is David Gesswein's BeagleBone Black based MFM reader/emulator project.

http://www.pdp8.net/mfm/mfm.shtml

It reads the raw flux transition times, which permits emulation of the drive itself. For reading the actual data, he has done some work for the common controllers as well.

Christopher

kb2syd
September 8th, 2015, 10:10 AM
Since nearly every company that made MFM controllers used a different protocol to LLF the drive this 'dongle' you are dreaming about would need to encompass a multitude of protocols in order to cover most of the necessary bases. :-)


Using this logic, Seagate would have to make a version of the drive for every controller. The protocol to format the drive wouldn't matter if the emulator just emulated the MFM interface. The controller itself would still handle the protocol.


Edit: I didn't see the OP's request to read data off this drive, even though that was what was asked for. For that, yes, you would need the right controller to make sense of what is on the drive. Wow did I miss that. All that sunk in to my head was the emulator angle and I immediately thought of writing data, not recovering. Ugh, did I miss that by a mile. What Stone said is correct for reading data from the drive. I couldn't make strike through work.

SomeGuy
September 8th, 2015, 10:45 AM
Using this logic, Seagate would have to make a version of the drive for every controller. The protocol to format the drive wouldn't matter if the emulator just emulated the MFM interface. The controller itself would still handle the protocol.
We are mainly talking about reading an already formatted drive here. Almost every different model of MFM and RLL controller did its own thing that made its low-level format incompatible with every other MFM or RLL controller.

There are USB adapters that you can plug in to an IDE drive to magically read all the content. This only works because the IDE drives hide the low level stuff from the rest of the system.

An MFM DRIVE (not controller) emulator may not need to know about the low-level implementations because it would just store raw bits and simulate spinning them around. Those can be useful for non-IBM PC machines, machines with integrated hard drive controllers, or other computers where an XT-IDE can not be used. But unless someone built a kryoflux-like device for MFM/RLL hard drives, that would not be much use for reading an existing drive.

krebizfan
September 8th, 2015, 10:59 AM
Some industrial systems used stock controllers that attached to standard busses. Take another look at the system the drive was taken out of. It may be possible to remove the MFM controller and place it into a standard computer which could result in successfully reading the drive. Or provide a lead on getting a matching controller.

Stone
September 8th, 2015, 11:41 AM
Using this logic, Seagate would have to make a version of the drive for every controller. The protocol to format the drive wouldn't matter if the emulator just emulated the MFM interface. The controller itself would still handle the protocol.


We are mainly talking about reading an already formatted drive here. Almost every different model of MFM and RLL controller did its own thing that made its low-level format incompatible with every other MFM or RLL controller.Bravo... It's good to see that somebody understands the relationship between MFM drives and their associated controllers. :-)

kb2syd
September 8th, 2015, 12:06 PM
Bravo... It's good to see that somebody understands the relationship between MFM drives and their associated controllers. :-)I understand that, what I didn't understand was the OP's request to read the data on the drive. And to top it off, he had stated it pretty obviously. Guess I need more coffee (or less).
Sorry for the added noise.

Stone
September 8th, 2015, 12:12 PM
Guess I need more coffee (or less).A beer will probably do quite nicely at this point. :-)

rcooke
September 8th, 2015, 12:34 PM
Thanks Everybody! Digging around here, and some googling I have:

People are building emulators to replace the drive:
- http://www.pdp8.net/mfm/mfm.shtml
- http://fafner.dyndns.org/~heuberger/DE0RL/README33.pdf
- http://discferret.com/wiki/DiscFerret

Commercial emulators:
- http://www.datex-dsm.com/dtx300-mfm-emulator-can-replace-all-existing-disk.html

I found mention of 2 more commercial products, but they - and datex - and diskferet - seem to have dropped out of production.

The PDP8 emulator looks like my preferred choice - the heuberger emulator looks like more work. But I would talke a closer look at them both before making a final decision.

I thought, browsing through the source code for the PDP8 emualtor that they read-in the data stream from a drive, then analyse the data to figure out the encoding. Or did I miss something in the software?

rcooke
September 8th, 2015, 12:35 PM
I read mention of XT-CF or XT-IDE card, but have not found their home pages yet.

modem7
September 8th, 2015, 03:40 PM
I read mention of XT-CF or XT-IDE card, but have not found their home pages yet.
https://www.lo-tech.co.uk/wiki/XT-CF-lite

http://www.malinov.com/Home/sergeys-projects/xt-cf-lite

http://www.vintage-computer.com/vcforum/showthread.php?29202

rcooke
September 11th, 2015, 05:29 AM
Thanks @cdbachmann!

I found that page reading other posts here, but I missed the important technical detail: "reads the flux transitions".

Very cool.


Rich.

rcooke
September 11th, 2015, 06:39 AM
https://www.lo-tech.co.uk/wiki/XT-CF-lite

http://www.malinov.com/Home/sergeys-projects/xt-cf-lite

http://www.vintage-computer.com/vcforum/showthread.php?29202


@modem7 Thank you! Reading those links now.....

I'm still waiting for the client to drag in to me or photograph what this drive came out of. I have a vague hope it will be a PC embedded into the machine. Or I would settle for a well known commercial MFM controller.....

rcooke
September 12th, 2015, 12:58 PM
I have pics of the controller card, the control cabinet, and what the boot screen looks like - with drive error.

2658326584265852658626587

You can recognize what looks like part of a PC/XT chassis where the I/O cards are attached. That really long card is likely a motion control card to run the machine's motors. Although I would like a photo of it showing the part number to be sure.

Ideally I would replace the whole control system with something (anything) newer. But the least disruptive (and cheapest) fix I think is an ISA bus adapter for Compact flash or other SSD.

If anybody knows of any other products like that, not mentioned above already, please post them. Or if you have one to sell e-mail me.

Rich.

modem7
September 12th, 2015, 07:33 PM
I have pics of the controller card, the control cabinet, and what the boot screen looks like - with drive error.
In case you have not worked it out yet, the hard disk controller is a DTC model 5150CR.

On it, the chip labelled "BXD07" is a BIOS expansion ROM. A ROM image of BXD07 is at [here (http://www.minuszerodegrees.net/rom/rom.htm)].

The "1701" you see at boot up is produced by code in that ROM. The sequence is:
1. Motherboard starts.
2. As part of the motherboard's initialisation sequence, the motherboard ROM looks for BIOS expansion ROMs.
3. The motherboard ROM finds the BIOS expansion ROM on your DTC 5150CR and does a crude checksum of it to ascertain confidence of the ROM's integrity.
4. The motherboard ROM passes execution to the part of the BIOS expansion ROM that is to do any required initialisation.
5. The initialisation code in the 5150CR's BIOS expansion ROM discovers a problem of some sort, and indicates that by displaying "1701".
6. The 5150CR's BIOS expansion ROM returns execution to the motherboard ROM.

1701 is a generic error produced my many XT-class hard disk controllers, reflecting a problem in the hard drive system, "system" being the key word. All kinds of things can cause it, examples being (but not limited to);
* Hard drive has become faulty.
* Lack of power to hard drive.
* Hard disk controller has become faulty (partially).
* A poor connection has developed between the hard disk controller and some of the contacts in its socket.
* A cabling issue.
* A new hard drive has been attached to the controller, but the drive has yet to be 'initialised' (low-level format) by the same make/model of controller.
* Hard drive not jumpered correctly.


I presume that the "Disk Bad" message is produced by the motherboard BIOS in relation to the floppy drive. I write that because:
1. "Disk Bad" does not appear in the ROM image of the BXD07 at [here (http://www.minuszerodegrees.net/rom/rom.htm)], and
2. "Test 640K" (a message from the motherboard BIOS) appears between "1701" and "Disk Bad".

rcooke
September 14th, 2015, 06:37 PM
In case you have not worked it out yet, the hard disk controller is a DTC model 5150CR.



Haha, Thanks! I might not be the sharpest knife in the drawer, but I did research the "5150 CR" sticker. And I kinda recognized the mfr name on the card..... I guess I really am kinda old.

As I said earlier, the machine shop is family owned and run. They don't have the budget to replace the entire control system.

I think the best value would be to change them to a PC bus expansion card that drives a Compact Flash or other SSD device.

What I can't remember is how compatible PC bus and ISA bus are.

I assume its PC bus since the BIOS says 8088.

Or have I mis-remembered this wrong?

(my first PC was an Apple ][+ I always found these PC beasts mildly confusing)

Thanks in advance!

Rich.

EDIT:
I just consulted: https://en.wikipedia.org/wiki/IBM_Personal_Computer#XT
And confirmed the XT's 8-bit ISA bus was expanded to 16-bits in the AT but maintained forward compatibility with 8-bit cards.

modem7
September 15th, 2015, 04:39 AM
What I can't remember is how compatible PC bus and ISA bus are.
I assume its PC bus since the BIOS says 8088.
Or have I mis-remembered this wrong?
These days, people mostly use the terms of 8-bit ISA and 16-bit ISA.


EDIT:
I just consulted: https://en.wikipedia.org/wiki/IBM_Personal_Computer#XT
And confirmed the XT's 8-bit ISA bus was expanded to 16-bits in the AT but maintained forward compatibility with 8-bit cards.
Although not 100% compatibility.
For example, there are some 8-bit ISA cards designed for the PC and XT that cannot operate reliably/properly at the faster speed that AT-class computers run their ISA slots at.

rcooke
September 15th, 2015, 06:32 AM
For example, there are some 8-bit ISA cards designed for the PC and XT that cannot operate reliably/properly at the faster speed that AT-class computers run their ISA slots at.

Oh right. That stirred up some dusty memories...


Thanks!

So, is there any particular vendor or group I should give my business too?

Looking to buy an ISA to CF card or equivalent.

rcooke
May 14th, 2016, 07:00 AM
For completeness and historical reference, I was able to repair this machine with an ISA IDE card and a CompactFlash drive module. The machine is up and running better than ever!

This is a link to the forum post where I worked out the hardware needed, and recruited help testing it (since I don't have a working XT machine).


link (http://www.vcfed.org/forum/showthread.php?49338-Looking-for-an-8-bit-ISA-(XT)-IDE-Compact-Flash-or-SD-drive-card&highlight=)


Thanks to everybody for helping me with this!