8bit Friendly ISA VGA cards

[Moogle!]

I would like to add 3 cards I have confirmed to work in 3 different 8 bit systems. These were not extensively tested beyond booting into DOS 6.22. The systems tested were an IBM XT 5160 with the 1982 BIOS; a Hedeka 919, which is an odd 286 based XT with only 8 bit slots and a switchable 10Mhz / 4.77Mhz mode; and an XI 8088 in a third party backplane that is all 16 bit slots with BIOS 0.9.9.

There is a Video Seven VEGA VRAM, an OEM Trident Board, and an Everex with the Accumos AVGA1 chipset. The Video 7 card needs switches 6 and 7 to be in the off position, the Trident and Everex seem to autosense. I have found that using the XI8088 with the 16 bit backplane seems to throw off some cards, such as one of the ATI VGA Wonders.

 

[Moogle!]

Something to beware of, just because the chip supports 8 bit mode doesn't mean the card does. Here are two cards I cannot get to work in any of the three systems mentioned in the preceding post. I am reasonably certain The Oak 0TI037C card simply does not appear to support 8 bit mode despite the datasheet mentioning PC support.

I am not certain what all the switches on the Cardinal do, since there is no documentation to be found anywhere, but the switches are in the state I received it in, and it does not show a display in an 8 bit slot.

 

[Eudimorphodon]

Oak 0TI037C card simply does not appear to support 8 bit mode despite the datasheet mentioning PC support.

The *only* thing that's 16 bit on an OTI-037 card is BIOS access. I mean, literally, that's it. The VGA itself is *entirely* 8 bit. If one of those jumpers doesn't set 8-bit mode then maybe this one is trying to autodetect and failing?

 

[Moogle!]

The *only* thing that's 16 bit on an OTI-037 card is BIOS access. I mean, literally, that's it. The VGA itself is *entirely* 8 bit. If one of those jumpers doesn't set 8-bit mode then maybe this one is trying to autodetect and failing?

VP42B

It would seem none of the jumpers control 8 bit access. I know my 067 card had jumpers that had to be changed.

 

[Eudimorphodon]

Looking at the photo of the card it’s… weird. Found another set of front and back photos here:

VGA Legacy MKIII - Oak OTI-037C

Basic VGA controller. Palcal's cards: Vlask's cards: Zaatharen's...

vgamuseum.info

And… I know this is probably a multi-layer circuit board, so there could be traces buried, but it almost looks like there aren’t any traces running from the 8-bit side of the board to the ODD ROM chip’s data lines? (there are address lines bridged over) Unless there’s another set buried in there it almost looks like this card may well be “obligated” to run in a 16 bit slot?

FWIW, that would be a terrible design choice. It’d likely cause conflicts with any other card you might install that has 8 bit BIOS ROMs.

 

[Zare]

I have issues with TVGA9000i-2 in 8bit mode. It doesn't work. The machine doesn't have an error beeper.

Another card tested is TVGA8900C which works jumperless. In XT it reports 256kB memory, in Pentium machine it reports 1M of memory.

When I plug TVGA9000i-2 in Pentium it boots with 512kB regardless of being jumped to 8 or 16 bit and it always has (16) at the end of the version string.

 

[Zare]

I might add that reason why I want 9000 instead of a working 8900C is the height profile. The machine can take a card about a millimeter taller than above attached TVGA.
So if anyone has any tips of what other cards to look at I would appreciate it. The Everex from Moogle!'s post looks like a good fit but I can find only sellers from USA in Ebay.

 

[boggit]

[h="1"]TSENG[/h]

• ET4000 chipset XVGA based card from Focus Information Systems Inc. (autosense)
• ET4000 chipset from Diamond Speedstar. (switches 1/3 off)

Would a w32 version of an ET4000 based 16-bit VGA card work in an 8-bit ISA slot?

From what I've understood, the w32 ones were released relatively late, so I figured it might not work too well in an 8-bit slot, but maybe someone here knows?

 

[dr.zeissler]

Diamond Speedstar 24X is compatible with XT machines according to the manual:

View attachment 1249303

can confirm that, worked in Tandy100 RL/HD.

 

[dr.zeissler]

I did a bit of an experiment where I made Anamorphic 800x600 32k color images and hooked up my Vendex to my 65" LG OLED. I made a video with several slide show images. I attached some of the pictures of the OLED and a zip file with the Anamorphic 800x600 images in case anybody else has their old PC connected to a widescreen display and wanted to see how they look. In the video I removed some of the image loading but you can still get a sense of how slow it is even with the 286 accelerater.

Anyway, it does show how the Diamond Speedstar 24 is a) compatible with an 8 bit slot and b) can do 32k with a VESA 1.2 Driver.

If you do hires gfx (256+ colors) on an early VGA card, please use TGA as format and quickview 1.3 as viewing program.
it loads and displays the big files like charm...even on very lowend machine. example (286/8 1024x768 256colors)

 

[chjmartin2]

If you do hires gfx (256+ colors) on an early VGA card, please use TGA as format and quickview 1.3 as viewing program.
it loads and displays the big files like charm...even on very lowend machine. example (286/8 1024x768 256colors)

That is fast...

 

[Zare]

Do you guys think disassembling the VGA BIOS dump from the internet should be an almost correct indication whether the card can run in 8088 XT, prior to purchase?
Are there 16bit VGA ISAs that don't require 286 and run happily on 8086?

 

[Eudimorphodon]

Are there 16bit VGA ISAs that don't require 286 and run happily on 8086?

There have been quite a few VGA cards with 16 bit connectors mentioned in this thread that work fine on 8088/8086 machines...

Do you guys think disassembling the VGA BIOS dump from the internet should be an almost correct indication whether the card can run in 8088 XT, prior to purchase?

Probably, although I'd hesitate to say it's a 100% guarantee. Just on this page of this thread someone posted a picture of an OAK037-based card (the '037 is an entirely 8-bit VGA chip, and OAK BIOSes seem to have mostly been 8-bit friendly up through at least the '077) that doesn't work in an 8-bit slot because the ROM chips are wired up to *only* work in 16 bit mode... which is actually a catastrophically bad design flaw, because the way bus sizing works on the ISA bus means this card might not work/cause problems in computers with 16 bit slots that have any 8-bit cards plugged in alongside them.

I also have a vague memory that some very late 16 bit VGAs (some Cirrus Logic-based cards?) that even if they had an 8-bit BIOS would still fail in an XT because they rely on the LA17-LA23 address lines on the 16 bit connector. So, in short, there's always the possibility that an individual card, even if it uses a chipset that's known to work in 8-bit mode and has a BIOS that doesn't use 80186+ instructions, could have implementation issues that exclude it from 8-bit slots.

 

[Zare]

There have been quite a few VGA cards with 16 bit connectors mentioned in this thread that work fine on 8088/8086 machines...

Those cards work in 8 bit mode on 8088 - I run TVGA8900D that way, didn't aim for that but wanted to exclude the option that some card's ROM has 8086 opcodes only but card relies on 16bit bus.

Probably, although I'd hesitate to say it's a 100% guarantee. Just on this page of this thread someone posted a picture of an OAK037-based card (the '037 is an entirely 8-bit VGA chip, and OAK BIOSes seem to have mostly been 8-bit friendly up through at least the '077) that doesn't work in an 8-bit slot because the ROM chips are wired up to *only* work in 16 bit mode... which is actually a catastrophically bad design flaw, because the way bus sizing works on the ISA bus means this card might not work/cause problems in computers with 16 bit slots that have any 8-bit cards plugged in alongside them.

I also have a vague memory that some very late 16 bit VGAs (some Cirrus Logic-based cards?) that even if they had an 8-bit BIOS would still fail in an XT because they rely on the LA17-LA23 address lines on the 16 bit connector. So, in short, there's always the possibility that an individual card, even if it uses a chipset that's known to work in 8-bit mode and has a BIOS that doesn't use 80186+ instructions, could have implementation issues that exclude it from 8-bit slots.

So those are some cases where ROM disassembly might be misleading.

 

[Plasma]

Are there 16bit VGA ISAs that don't require 286 and run happily on 8086?

What system is this for? I think most 8086 PCs had proprietary 16-bit slots, if they had any.

 

[Zare]

I really can't tell, just looking at the possible caveats; consider that at end of 1986, 16-bit ISA was around for couple of years already, while the best selling PC in Europe was Olivetti with 8086 and proprietary 16 bit slots. I don't know of any system in question, I don't know for 100% that it's technically doable, but looks to me there was a market demand for 8086 with industry standard 16 bit cards.