More on ISA cards / Flashlite 186 SBC

The discussions here about ISA cards have brought to mind a possible solution to a problem I have; how to make a little board that can do

640x480@15/16bpp video on analog VGA, with a build cost of
Reply to
Lewin A.R.W. Edwards
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Lewin A.R.W. Edwards wrote

In my time at Arcom Control Systems, we did a lot of work with PC peripherals connected to 80186/80188 boards, and we created a product (SourceGraph) to drive specific VGA cards.

You could strike it lucky with a random VGA card, or you could find it impossible to get working. It is amazing how much PC-specific stuff is in a VGA BIOS - as a board manufacturer, we were able to get access to some BIOS source code, so we knew eaxctly how PC-dependant they were. The 80186 is PC-code compatible, but key peripherals (timers & interrupt controller) have different addresses and functionality, and the memory map probably isn't the same as a PC.

To give one trivial example, we had a VGA board that worked fine in text mode, except that all numeric characters 0-9 were corrupt. It turned out that it was loading the numeric font (but not the text font!) from the old MDA font located in the motherboard BIOS, so we had to fake this at the same address in the 80188 memory space.

I think the reduced production costs could be overwhelmed by increased development costs - and who's to say that the ISA card you buy today will still be available tomorrow?

Jeremy Bentham Iosoft Ltd.

Reply to
Jeremy Bentham

Then you're the gentleman to whom I need to speak :)

I didn't think of issues like that. Hmm. Well, I still don't think this precludes my approach. I don't actually want any of the card's BIOS functions - not even text output. I have my own engine for all that. The ONLY use for the card's BIOS would be to set the video mode to a 640x480x15/16bpp mode. I am assuming that any ISA card I can find has its aperture control registers well-enough documented in XFree86's sourcecode for me to be able to write my own bank select code (see below)

I've reverse-engineered VGA BIOSes and my experience is that it takes

1-2 weeks to turn a 32K BIOS into a quality, commented, re-assemble-able piece of sourcecode. I don't want to do that.

Well, I'm sure it won't be. Let me elaborate on my fiendish master plan: I want to use the ISA bodge job for market-test purposes. The product in question is experimental; we don't know how it will go across with consumers. I wouldn't anticipate making more than 25-50 of these devices with that bodge. I would think I can source that number of fairly similar cards. I was thinking of using, say, Trident

8900-series cards, which are *largely* intra-family code-compatible (certainly the stuff I'd need to program is the same amongst the 8900C/CL/CX/CXi).

The EVB for the SED1354 is also an ISA card. So once I have the hacked-up version working and shipping, I can get the SED1354's EVB working using the same hardware. Once THAT is working, I can make a small custom PCB with a 1354 on it, to stick on top of the Flashlite. That custom board would be [reasonably] producible, and it also gives us a couple of other benefits.

Reply to
Lewin A.R.W. Edwards

in a

BIOS

will

Wonder if the VGA related emulator code in the Bochs project would be of any use?

Reply to
DM McGowan II

Not sure exactly what use it would be... because whatever chipset I use will have special hidden registers required to set those SVGA modes. But anyway, I've decided to give this project a try. I'm sitting on my hands waiting for the Powers that Be to call JK with the company credit card so I can get the EVB.

It also kind of hinges on how long the "186-ish" CPU on the board will take to run my code. I need hands-on testing.

Reply to
Lewin A.R.W. Edwards

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