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romanon
May 23rd, 2017, 09:26 AM
Hello, some questionst here:

1) was ever supplied ST-506s with early IBM XTs or ST-412 was the first?
2) can be ST-506 connected to IBM XT Xebec HDD controller? Is there support for this drive?
3) can be ST-506 connected to IBM AT HDD controller? Is there support for this drive?

As i know, ST-506 is missing IBM logo on black front panel so maybe was not designated for IBM PC family..

38749

(i dont have any, only interesting in)

Thanks

Chuck(G)
May 23rd, 2017, 09:46 AM
10MB was the first drive for the XT. However:

You can use an ST506 if your controller can support a slower 3 msec. (unbuffered) seek. Not all controllers can.

To be more explicit, an ST412 (and later) drives will count up step pulses issued as fast as one every 25 usec. and then move the head carriage to the appropriate place and then assert SEEK COMPLETE. The 506 does not count seek pulses, so does not accept a step pulse until the previous one has been completed (think of it as a big floppy drive).

vwestlife
May 23rd, 2017, 10:25 AM
2) can be ST-506 connected to IBM XT Xebec HDD controller? Is there support for this drive?
Only if you have "variation #2" of the Xebec controller and add the missing DIP switch block to select the drive type:

http://www.minuszerodegrees.net/ibm_xebec/ibm_xebec.htm

romanon
May 23rd, 2017, 10:38 AM
Only if you have "variation #2" of the Xebec controller and add the missing DIP switch block to select the drive type:

http://www.minuszerodegrees.net/ibm_xebec/ibm_xebec.htm

Are you sure? There is no switchable variant for 5MB disk, only 10 or 20 megs

Chuck(G)
May 23rd, 2017, 10:53 AM
When I ran an ST506 from a Xebec controller, I modified the drive table for the proper parameters. It's pretty straightforward--the controller supports 3msec step rates and the other drive parameters are self-explanatory. If you've modified other BIOS ROMs, it should be a walk in the park.

vwestlife
May 23rd, 2017, 11:31 AM
Are you sure? There is no switchable variant for 5MB disk, only 10 or 20 megs

If you add a switch block to variation #2, there is a setting for 306 cylinders and 2 heads (5 MB) with the ST-506's 3 ms step rate:

http://www.minuszerodegrees.net/ibm_xebec/variation_2_switch.htm

romanon
May 23rd, 2017, 11:44 AM
If you add a switch block to variation #2, there is a setting for 306 cylinders and 2 heads (5 MB) with the ST-506's 3 ms step rate:

http://www.minuszerodegrees.net/ibm_xebec/variation_2_switch.htm

Oh i see, I thought that variation 2 has same switching like variation 3

Chuck(G)
May 23rd, 2017, 11:49 AM
...and my point was that you don't even need variation 2 or a switch block if you're willing to re-burn the BIOS PROM.

romanon
May 23rd, 2017, 07:17 PM
...and my point was that you don't even need variation 2 or a switch block if you're willing to re-burn the BIOS PROM.

I have variation 2 controller so this is easier solution imho...
What about variation 3 and ST-412 (type 1)? According to table there is not option to 306/4/17 with WPC=128? That is little bit strange or?

Aaand what about PC AT and ST-506? Can it work?

Chuck(G)
May 23rd, 2017, 08:19 PM
WPC for later drives isn't used.

You can use an ST-506 on a PC AT if you have a controller that supports non-buffered seek (i.e., it can issue step pulses 3 msec apart).

modem7
May 24th, 2017, 01:46 AM
...and my point was that you don't even need variation 2 or a switch block if you're willing to re-burn the BIOS PROM.

I have variation 2 controller so this is easier solution imho...
The drive table resides in the controller's BIOS ROM.
On the Xebec cards supplied in the IBM 5160, that ROM is an MK36xxx series PROM (or equivalent), not a 2764.
If you want to use a 2764, you will need to use an adapter.
Note that using an adapter might mean that you end up with a controller that occupies two slots - see [here (http://minuszerodegrees.net/temp/3/temp_x92d35yy64k336481262875.jpg)].

Xacalite
May 24th, 2017, 06:31 AM
What about variation 3 and ST-412 (type 1)? According to table there is not option to 306/4/17 with WPC=128? That is little bit strange or?
Yes, it *is* strange.
http://minuszerodegrees.net/ibm_xebec/ibm_xebec.htm
"Either IBM did not consider WPC important (unlikely), or a mistake was made, or perhaps Seagate informed IBM that WP on all cylinders of the ST-412 is acceptable."

Chuck(G)
May 24th, 2017, 07:47 AM
I don't recall what I used for a BIOS PROM--probably a 2532. At any rate, it wasn't a big problem back then. No adapter needed.