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Earth Computer Technologies PWB-5030 (Chips F65550) 2MB PCI Card Reporting only 1.5MB...

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First post, by Ozzuneoj

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Well, here's another weird one. This card is reporting only 1.5MB of RAM in Windows 98SE (dxdiag), and is only giving me 16bit color support... absolutely no 24bit color options.

The extremely detailed datasheet for the F65550 mentions that memory configurations can be limited when making use of additional display options. Page 26 specifically mentions "Because of pin sharing on the 65550, video capture/playback precludes an external STN-DD buffer" and 1.5MB is mentioned as one of these limitations. The card does have a large second output connector and a set of switches for "Panel Type", which I have played with a bit and it makes the pre-windows screens change shape when I change the jumpers but it doesn't change the memory or resolutions available in Windows with drivers installed.

I don't really understand most of what the datasheet has to say about this topic though. Is this is something I can work around on this particular card with jumpers\switches or a BIOS change? Or maybe a couple of the empty resistor locations would switch it to 2MB single-display mode? I highly highly doubt that this thing will ever have a display connected to that funky secondary output.

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Anyone have any ideas? It's a really nice card. Output is clear, it is very responsive and the DOS mode font is really unique.

BTW, I have tried moving the jumper between the main chip and the memory. Putting it in either 1-2 or 2-3 doesn't seem to make any difference. If I take it off completely the system will POST but there will be no display.

Now for some blitting from the back buffer.

Reply 1 of 2, by douglar

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Ozzuneoj wrote on 2025-12-22, 20:50:

Well, here's another weird one. This card is reporting only 1.5MB of RAM in Windows 98SE (dxdiag), and is only giving me 16bit color support... absolutely no 24bit color options.

That's pretty strange. I thought VGA display memory is limited to 256KB, 512KB, 1MB, 2MB, or 4MB because of how VGA works the VGA memory address lines. Looks like the card has 2MB of chips on there. Maybe something is funny with the device driver?

Reply 2 of 2, by Ozzuneoj

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douglar wrote on Yesterday, 21:38:
Ozzuneoj wrote on 2025-12-22, 20:50:

Well, here's another weird one. This card is reporting only 1.5MB of RAM in Windows 98SE (dxdiag), and is only giving me 16bit color support... absolutely no 24bit color options.

That's pretty strange. I thought VGA display memory is limited to 256KB, 512KB, 1MB, 2MB, or 4MB because of how VGA works the VGA memory address lines. Looks like the card has 2MB of chips on there. Maybe something is funny with the device driver?

As mentioned in the OP, there seem to be some situations where these cards use 1.5MB to facilitate some additional features. I don't really understand it but the datasheet goes in to a lot of detail for those smarter than me. 🤣

Also, the ET6000, for example, can have 2.25MB due to the odd sizing of some MDRAM chips. I guess this was done to allow resolutions that are just barely beyond the 2MB limit.

The use case for this card is very different though, so I think the odd 1.5MB and 2.5MB configurations apply when parts of the chip (that would be connected to more memory) are reused for specific industrial or mobile applications. Since it is using normal RAM chips, part of the chips just seem to just go unused in those situations.

Now for some blitting from the back buffer.

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