IBM VGA chips - for study/discussion

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IBMMuseum

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Sep 1, 2021, 3:13:03 PMSep 1
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15F6864: Extremely common on PS/2 planars - known pinout from Model 30 286 schematics, page 6 of 6, https://www.ardent-tool.com/docs/pdf/schematics/m30-286_sch.pdf

92F0616: Apparently pin-compatible with the 15F6864 - I have one on a Model 70-Axx planar

90X8941: Listed only on the 8580-Axx planar - I also have one on a Model 30 286 with the single 40-pin EPROM planar, so also likely pin-compatible

90X8999: I have one on a Model 30 286 with the dual 28-pin EPROMs planar, and there is mention of someone here in an old topic that had one on a Model 70 'Type 1' planar - also likely pin-compatible

72X8287: The "metal-can" version on the Model 80 'Type 2' planar and 8-bit VGA adapter for the Model 30 - This is the only IBM VGA chip that isn't (PQFP) plastic and with a Seiko-Epson marking to top

Tomas Slavotinek

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Sep 5, 2021, 2:17:03 PMSep 5
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Interesting topic and something that's definitely worth documenting...

On 1.9.2021 21:13, IBMMuseum wrote:
> 90X8941: Listed only on the 8580-Axx planar - I also have one on a Model 30 286 with the single 40-pin EPROM planar, so also likely pin-compatible

This variant is also used in selected PS/55 5550 machines and standalone
Japanese display adapters. And then some 55 SX, 65 SX, 70 T2, and maybe
other PS/2 planars.

Possibly Japanese origins?

IBMMuseum

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Sep 5, 2021, 4:04:41 PMSep 5
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> Possibly Japanese origins?

I've stated before that I think Seiko-Epson Japan got connected to IBM for the PC Convertible (static RAM and the BIOS chips are marked with their logo) with the flat-panel flailings. IBM bought a TFT plant from Seiko-Epson, although it is viewed as ramping up for the PS/55 series. The Model 30 and PC Convertible share some BIOS calls - MCGA and VGA development needs to be probed further, although Eric delidding the early MCGA Gate Array chip showed IBM markings inside.

I envision a pinout diagram of the chips - at least I think it will be that IBM developed the 72X8287 chip (making video standards was nothing new for them) and turned it over to Seiko-Epson for line production. The models with which versions of the chips are installed - and date-code decoding - can be definitive too. Let's get started!

Tomas Slavotinek

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Sep 5, 2021, 4:54:44 PMSep 5
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This brings some interesting and rather important questions.

Was IBM Japan fabless initially? I assume that chips marked as "98" were
actually manufactured by IBM Japan, is that correct? Or why exactly they
cooperated with Seiko so closely and so often? Volume limitations? More
advanced or mature process? Better yields/cheaper production?

Anyone? Greg?

IBMMuseum

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Sep 27, 2021, 3:36:52 AMSep 27
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> >> ...And then some 55 SX, 65 SX, 70 T2, and maybe other PS/2 planars.

Yes, you caught that the 90X8941 is on the 65SX and Model 70 'Type 2', and seems to be substituted into other models at times (Model 25 286 and 30 286, and 55SX 'Type 2' are known occurrences). The 90X8999 and 92F0616 seem to be much rarer substitutions.

Louis Ohland

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Sep 29, 2021, 10:01:05 AMSep 29
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Evil Dave, what are the date codes for the VGA ASICs?

If I understand your Delphic utterance, there are only TWO metal capped
VGA, the 8580 Type 2 system board -AND- the Model 30 [ISA] VGA adapter.

From DIMM memories, VGA would be on all 8525, 8530, 60, 65, 70, and 80.

IBMMuseum

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Sep 29, 2021, 1:25:49 PMSep 29
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> Evil Dave, what are the date codes for the VGA ASICs?
>
> If I understand your Delphic utterance, there are only TWO metal capped
> VGA, the 8580 Type 2 system board -AND- the Model 30 [ISA] VGA adapter.
>
> From DIMM memories, VGA would be on all 8525, 8530, 60, 65, 70, and 80.

The 72X8287 'metal-can' VGA is on the initial release (and months-later) PS/2s except for the Model 70: 50-021, Model 60, Model 80 ('Type 1' and 'Type 2'), and 8-bit board for the Model 30. P/N 90X8941 is the only version that has usage in Japanese production, although there are some implementations where Japanese influence is unknown (65SX, 70 'Type 2', one of my Model 30 286 samples). 15F6864 is in most later VGA implementations, and in rare instances, substituted with the very uncommon VGA P/N of 90X8999 and 92F0616.

You will just need to read date codes from the pictures...
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