...

There´s also a nice riser card for ISA/PCI cards

When I got this board it wouldn`t start due to some damaged traces near the CPU socket that were easy to repair with thin wires

The latest BIOS - 1.07 - can still be obtained from the NCR website
http://www5.ncr.com/support/support_drivers_p … pc_library_3348

Floppy drives are NOT recognized by this mainboard when they are connected to the second connector of the floppy cable (the one behind the wire-crossing). Floppys need to be connected to the first connector instead.

The board offers 50, 60 and 66 MHz FSB and multiplicators x2 and x1.5.
Jumper JP2 switches between core voltages 3.3V and 3.45V.
An additional VRM socket could also be soldered in to provide 2.8V for Pentium MMX but the BIOS doesn´t know any MMX models and given the multiplicator limitations I don´t thik it would make any sense.

Here´s the VAFC "feature connector" that can be enabled in the BIOS menu, it´s not populated in later revisions of this board.

t.b.c.

There´s some progress here. This board has a Socket 5 CPU socket, but is prepared for the connector for an additional 2.8V VRM. I suspected it´s in fact capable of split voltage AKA Socket 7.
So I fitted the 2x15 pins for the VRM in and cut the traces between pin pair 6 and 7, put one of my VRMs on top and a Pentium MMX 233MHz in the socket:

Then I set the multiplier dip-switch to x1.5 and started the system. To my disappointment the MMX was running at 133 MHz, it didn´t respond to the 1.5 multi by interpreting it as x3.5.
Checked BF1 -> open,
checked BF2 -> open,
checked BF0 (formerly BF) -> open.
On this mainboard the dip-switch releases BF0 from ground but there´s no pull-up resistor present to lift the BF0 pin up to Vcc. So I added a 4K7 resistor and voila

The next - and bigger - problem is the COAST cache module. FIC / AT&T obviously have a non standard pinout here that prevents regular COAST modules from being used.
I tested about 25 different COAST modules, all of them are either not detected or prevent the system from starting.

majestyk wrote on 2021-02-21, 11:15:

[...]

The next - and bigger - problem is the COAST cache module. FIC / AT&T obviously have a non standard pinout here that prevents regular COAST modules from being used.
I tested about 25 different COAST modules, all of them are either not detected or prevent the system from starting.

I don't think that pinout is the problem, rather the cache type. This board contains a VLSI 82C590 PowerCore chipset, which is pre-i430FX, so almost certainly also pre-PLB cache. That means it would need an async SRAM cache module. I've not been able to find a datasheet to confirm this assumption, but given you've thrown probably about every PLB config in existence against it, it seems more than likely.

This might well be the case, or both.
With PLB modules the machine won´t start at all.

Then I have a lot of "sync cache" modules like this:

Withe these the system starts bot no cache is being detected.

I couldn´t find any datasheet of the VLSI MCH so far.

I then compared the COAST pinout of this mainboard with this one:
download/file.php?id=82702&mode=view

All Vss connections are identical. Same goes for the "Vcc5" voltage. The connections for "Vcc3" differ. On the FIC socket Vdd3 is at pins 76, 68, 60, 52, 39, 25, and 15. It´s NOT at Pin7 as it should be according to the pinout documentation. Pin 7 leads to a pin of the MCH (VL82C591FC3) instead. Pin 6 at the COAST socket is NOT "NC" but also in use.
On all COAST sticks I own, the Vdd3 - Pins 76, 68,60, 52,39, 25,15 AND 7 are bridged.
So VDD3 (3.3V) is probably connected to some Data line when a standard COAST module is inserted.

And here´s another update:
It took a while - and some effort - to find the missing components.
First I upgraded Video-RAM so it´s 2MB in total now.

Then I managed to get hold of a working 256K cache-stick. It indeed has a proprietary and very rare pinout, but at least it´s a pipeline-burst type. (I doubt there exist 512KB ones).

Now this board runs a Pentium MMX 233 at 233MHz with an additional 2.8V VRM and working L2 cache. It´s a really nice LPX board now that can be upgraded with sound and ethernet using the (also proprietary) riser-card.

Brilliant stuff mate! I have an AT&T Globalyst 312 with a motherboard very similar to this, I believe. At one point I put in a 233 MHz MMX too, although it's also capped at 133MHz like yours was, and I've long since given up on finding a COAST module for it.
But my question here would be whether or not it is possible to run the processor at 233MHz without the VRM module?

Best regards.

If you want to use any split voltage CPU such as an Intel MMX233 you need an additional 30-pin VRM for the 2.8V core voltage.
These can still be found on Ebay.
You will also have to populate the 30-pin connector, cut a trace on the backside of the board and do the BF0 mod.

The performance gain is definitely worth the effort!

You can also use an interposer with built-in VRM instead.

Thanks for the reply! I'll have a look at trying to find a VRM and do the mod!

You´re welcome.

That´s what they look like:

Can you provide any information at all on this VRM and the cache module? I have a 373TPC with this same/similar mobo and I'd like to do some upgrayedd's! I found out the hard way that this isn't a standard COAST module as well.

majestyk wrote on 2021-10-29, 16:26:

And here´s another update: It took a while - and some effort - to find the missing components. First I upgraded Video-RAM so it´ […]
Show full quote

And here´s another update:
It took a while - and some effort - to find the missing components.
First I upgraded Video-RAM so it´s 2MB in total now.

psk2000_videoram.JPG

Then I managed to get hold of a working 256K cache-stick. It indeed has a proprietary and very rare pinout, but at least it´s a pipeline-burst type. (I doubt there exist 512KB ones).

psk2000_L2cache.JPG

Now this board runs a Pentium MMX 233 at 233MHz with an additional 2.8V VRM and working L2 cache. It´s a really nice LPX board now that can be upgraded with sound and ethernet using the (also proprietary) riser-card.

The VRM is a "Pentium I" type model as they were common during that period. If you´re seaching for VRMs today you get loads of later models (mostly Xeon) that cannot be used here.
Look out for the double-row 30-pin connector and linear regulators.
Or you could build your own VRM:
Gigabyte GA-586HX (Rev. 1.53)

As for the COAST module - I was able to trace down just one of them after buying and testing countless modules. You can see it in the picture above.
Recently there was a PSK-2000 complete with the original COAST-stick on Ebay - but sadly I missed it. I could have used it for my 2nd PSK-2000.

Thank you. Sounds like these are insane to find. Any idea of a standard COAST module could be manually rewired to work? Are the components different (they look similar to me but I haven't looked the ICs up) or is it just configure different?

majestyk wrote on 2022-05-27, 14:24:

The VRM is a "Pentium I" type model as they were common during that period. If you´re seaching for VRMs today you get loads of l […]
Show full quote

The VRM is a "Pentium I" type model as they were common during that period. If you´re seaching for VRMs today you get loads of later models (mostly Xeon) that cannot be used here.
Look out for the double-row 30-pin connector and linear regulators.
Or you could build your own VRM:
Gigabyte GA-586HX (Rev. 1.53)

As for the COAST module - I was able to trace down just one of them after buying and testing countless modules. You can see it in the picture above.
Recently there was a PSK-2000 complete with the original COAST-stick on Ebay - but sadly I missed it. I could have used it for my 2nd PSK-2000.

The two SRAM chips and the TAG-RAM chip are the same as on any regular 256K cache stick.
What´s different is the wiring, it differs from the COAST specification and many of the 160 pins are used differently.
The problem is there´s no datasheet of the VLSI memory controller available and the traces on the mainboard are very hard to follow so it´s a very tough job to find out what´s going where.

majestyk wrote on 2022-05-27, 19:33:

The two SRAM chips and the TAG-RAM chip are the same as on any regular 256K cache stick.
What´s different is the wiring, it differs from the COAST specification and many of the 160 pins are used differently.
The problem is there´s no datasheet of the VLSI memory controller available and the traces on the mainboard are very hard to follow so it´s a very tough job to find out what´s going where.

@majestyk There's a 620 on ebay right now with a coast module in it. It's not mine, but I saw it and thought of this thread. I can't PM yet or i would have just done that, but I thought you'd like to know.