Tandon TM-7521 (Targa?)

[davidrg]

I've got a Tandon TM-7251 (perhaps called a Targa?) here with a battery that went flat long ago. Its equipped with a Tandon TM-264 RLL hard disk hooked up to a Tandon branded RLL disk controller with no obvious model number, plus a pair of floppy drives.


Unfortunately I can't find any real information at all on this hardware besides a blurb written by the company that designed the case and this page that gives the supposed parameters for the drive.

I can boot from floppy disk ok, and the hard disk sounds fine, but in order to do anything with it I of course need to configure it in the BIOS. It turns out holding ESC during the memory test will get you into the BIOS setup program, but the options there are extremely limited:

Only the settings in the top panel are editable and if there are any more beyond these I don't know how to get to them. Fixed Disk Drives just go from Type 1 through to Type 47 with an additional "Not installed" option. Unlike most BIOSes I've seen, you're not shown what the parameters for any of these drive types are and if there is a way to enter the drive parameters yourself I can't find it. If the drive types are the same as for other BIOSes, then this drive would appear to need a custom drive option.

I've tried booting with each of the 47 different options but none of them work. Could be the hard disk doesn't work anymore, or maybe it needs a low-level format, or maybe none of those 47 settings are correct for the drive. But given this is a Tandon drive connected to a Tandon RLL disk controller in a Tandon computer there must be some way to configure this correctly.

Has anyone out there ever seen one of these machines and perhaps knows how to configure it? Perhaps there is some documentation out there that I've missed?

 

[bburley]

Specs on the HDD;



I also have a slightly newer revision of the controller (not tested yet);



I suspect that the BIOS in the controller for low level formatting would be accessed with a command something like debug g=c800:5

It may even be possible that the computer BIOS should have Fixed Disk set to None and the drive completely handled by the controller card BIOS.

 

[davidrg]

Tried the debug command but just get a file not found error - possibly I'm doing it wrong, I've never used the debug command before.

 

[modem7]

I've got a Tandon TM-7251 (perhaps called a Targa?) here with a battery that went flat long ago.

We have seen strange symptoms caused by a dead battery, and so if you are not already, you should be looking into a replacement battery.

Only the settings in the top panel are editable ...

It looks like the second panel is a 'for information' one.

I suspect that the BIOS in the controller for low level formatting would be accessed with a command something like debug g=c800:5
It may even be possible that the computer BIOS should have Fixed Disk set to None and the drive completely handled by the controller card BIOS.

I do not see a BIOS ROM on the card. On the OP's card, the large chip that has a sticker on it, is an Intel 8749. That is a microcontroller.

Unlike most BIOSes I've seen, you're not shown what the parameters for any of these drive types

The early BIOS' are like that. You can boot to DOS, so try the DOS tool at [here]. If you are lucky, it will show you the drive parameter table in the motherboard's BIOS.

 

[modem7]

I can boot from floppy disk ok, and the hard disk sounds fine, but in order to do anything with it I of course need to configure it in the BIOS.

And you need to factor in that a previous owner may have caused a problem. E.g. Cable issues: on wrong connector; pin 1 not going to pin 1, etc.

You have an AT-class computer, and can boot to DOS. Try SpeedStor version 6.5. Inform SpeedStor that you have a TM-264, then see if a seek test moves the heads. If it does, then try a read test, etc.

(BTW. After informing SpeedStor that you have a TM-264, you may discover that SpeedStor has changed the 'Fixed Disk Drive 1' number in the motherboard's CMOS/BIOS SETUP to something that it thinks is appropriate for the drive, in preparation for a low-level format.)

 

[modem7]

Unlike most BIOSes I've seen, you're not shown what the parameters for any of these drive types are

The early BIOS' are like that. You can boot to DOS, so try the DOS tool at [here]. If you are lucky, it will show you the drive parameter table in the motherboard's BIOS.

And the SpeedStor software that I referred to can do the same thing, by using SpeedStor's /romlist switch:

A:\SSTOR65>sstor /romlist

The screen will clear, then SpeedStor will display the hard drive parameter table.

 

[davidrg]

Seems this drive doesn't match any of the predefined types in ROM, and SpeedStor doesn't know what a Tandon TM-264 is either:

MachineID=0xFC, ROMmfg=0, ROMrev=0, DOS=622, drives=1
SpeedStor=0, DOS=622

47 ROM table(s) found at f000:e401

Type   Cyls   Heads   Secs   Pcomp   Lzone   Ctrl
  1     306     4      17      128    305      0
  2     615     4      17      300    615      0
  3     615     6      17      300    615      0
  4     940     8      17      512    940      0
  5     940     6      17      512    940      0
  6     615     4      17      615    615      0
  7     462     8      17      256    511      0
  8     733     5      17      733    733      0
  9     900    15      17      900    901      8
 10     820     3      17      820    820      0
 11     855     5      17      855    855      0
 12     855     7      17      855    855      0
 13     306     8      17      128    319      0
 14     733     7      17      733    733      0
 15       0     0       0        0      0      0
 16     612     4      17        0    663      0
 17     977     5      17      300    977      0
 18     977     7      17      977    977      0
 19    1024     7      17      512   1023      0
 20     733     5      17      300    732      0
 21     733     7      17      300    732      0
 22     733     5      17      300    733      0
 23     306     4      17        0    336      0
 24       0     0       0        0      0      0
 25       0     0       0        0      0      0
 26       0     0       0        0      0      0
 27       0     0       0        0      0      0
 28       0     0       0        0      0      0
 29       0     0       0        0      0      0
 30       0     0       0        0      0      0
 31       0     0       0        0      0      0
 32       0     0       0        0      0      0
 33       0     0       0        0      0      0
 34       0     0       0        0      0      0
 35     809     6      17      128    852      0
 36     781     2      17      781    805      0
 37     781     4      17      781    805      0
 38     781     6      17      781    805      0
 39    1024     5      17     1024   1024      0
 40    1024     5      17      512   1024      0
 41    1024     8      17     1024   1024      0
 42     615     8      17      128    664      0
 43     820     6      17      820    820      0
 44     306     2      17      306    306      0
 45     306     6      17      306    306      0
 46     695     5      17      695    695      0
 47     981     5      17      981    981      0

I tried picking a random drive type and changing the cylinders and sectors per track to 782/26 but that just gives me this:
Trying to do anything with the drive or controller just results in various errors. I don't see any activity from the hard disk during any of this which is a bit suspicious as if I try booting from the hard disk with some random drive type I can hear the drive seek and the light flashes. Even trying to park the disk fails, while some random park.com claims to succeed and does at least manage to flash the drive LED. So I guess SpeedStor isn't compatible with the controller/BIOS/computer in some way?

It seems a bit strange that the BIOS doesn't support the factory hard disk at all - surely there must be some way of configuring this. I wonder if the OEM version of MS-DOS has some additional BIOS setup utilities that go beyond what the ROM-based setup offers.

 

[davidrg]

Found a German copy of Tandon MS-DOS 3.3 on Beta Archive. The Tandon Utilities are in English though. One of them lists all the supported drive types and their parameters:

The Tandon TM 264 isn't listed, but RLL drive type 37 isn't far off - same heads and sectors per track, just one less cylinder bringing the capacity from 41MB to 39.7 - good enough.

Another utility, fxprep, is for low-level formatting drives. Trying to format flashes the HDD LED a bunch, then it reports a hardware error:


So perhaps the drive is just dead.

 

[modem7]

It seems a bit strange that the BIOS doesn't support the factory hard disk at all - surely there must be some way of configuring this.

I see. All of the sectors-per-track figures are 17.

I wonder if the computer came supplied with drive overlay software on the TM-264.

Or is there BIOS expansion ROM code hidden somewhere on the controller, hard-coded to match the TM-264.

So I guess SpeedStor isn't compatible with the controller/BIOS/computer in some way?

Or there is a fault/problem somewhere. I wonder what bburley will experience.

Even trying to park the disk fails, while some random park.com claims to succeed and does at least manage to flash the drive LED.

If you start SpeedStor 6.5 with the /help switch, many other switches are shown.

A:\SSTOR65>sstor /help

One switch is /nodiskbios, described as, "Prevents SpeedStor from using its own BIOS". Maybe give that a try.

 

[davidrg]

Based on what the Tandon drives utility (drives.com) showed, it seems this BIOS has two separate tables - one for MFM drives and one for RLL. The first table matched what SpeedStor could see, while the second table was different and did include drives with 26 sectors-per-track. I guess the BIOS decides which table to use based on the installed disk controller - it is currently set to RLL and doesn't allow you to change it. No sign of any custom drive options so I assume it must have originally been set to RLL Type 37 - that is close enough to the 40MB some models of the machine were advertised with.

 

[modem7]

Based on what the Tandon drives utility (drives.com) showed, it seems this BIOS has two separate tables - one for MFM drives and one for RLL. The first table matched what SpeedStor could see, while the second table was different and did include drives with 26 sectors-per-track. I guess the BIOS decides which table to use based on the installed disk controller - it is currently set to RLL and doesn't allow you to change it. No sign of any custom drive options so I assume it must have originally been set to RLL Type 37 - that is close enough to the 40MB some models of the machine were advertised with.

That explains a lot.

Which means that it is the motherboard BIOS that is providing BIOS support, INT 13h, for the controller+drive.

... while some random park.com claims to succeed and does at least manage to flash the drive LED.

That PARK.COM is probably using the applicable INT 13 function to establish which cylinder the heads need to be parked on, then using INT 13's seek function to move (seek) the heads to that cylinder.

As for SpeedStor, SpeedStor's nodiskbios switch ("Prevents SpeedStor from using its own BIOS") suggests that by default, SpeedStor uses its own INT 13 functions, ignoring those that are in the motherboard BIOS or BIOS expansion ROM. That is not going to work for any non-standard controller (e.g. different I/O ports than the norm). So, as an experiment, I suggest that you see if you get anywhere using the nodiskbios switch.

 

[modem7]

As for SpeedStor, SpeedStor's nodiskbios switch ("Prevents SpeedStor from using its own BIOS") suggests that by default, SpeedStor uses its own INT 13 functions, ignoring those that are in the motherboard BIOS or BIOS expansion ROM. That is not going to work for any non-standard controller (e.g. different I/O ports than the norm). So, as an experiment, I suggest that you see if you get anywhere using the nodiskbios switch.

I was misled. A later SpeedStor manual describes NODISKBIOS much better, described as "Instructs SpeedStor not to install the disk overlay BIOS." That is a very different thing.

... while some random park.com claims to succeed and does at least manage to flash the drive LED.

Use of a particular PARK.COM results in a flash of the the drive's LED. If that PARK.COM and SpeedStor are using the same INT 13H functions, then I expect the execution of SpeedStor's seek test to also flash the LED.

BTW. If you want to play around with the INT 13H functions yourself, you can do that using DEBUG. For example, see the 'Function 0Ch - Seek to a specified cylinder' section at [here].

 

[davidrg]

Using /nodiskbios was enough to let SpeedStor actually talk to the controller and disk, though it thinks its only 17 sectors per track rather than 26. Otherwise, controller tests pass, disk seek tests pass, a few random read/write tests pass, but it turns out there are over a hundred media defects near the start of the disk making it unusable. I assume this is why the Tandon disk format utility refused for format it. Bit of a shame; perhaps the heads weren't parked whenever it was used last.

Complete opposite of the AT clone I tidied up last week - the old ST-238R started life with zero defects and however many decades later is still defect free.