IBM's PGA Adapter

From: Kev <co273_at_freenet.buffalo.edu>
Date: Mon Apr 23 16:28:51 2001

> Basically, it operates in 2 modes. The first is 'CGA emulation'. It does
> just about everything a real CGA card would do, with the exception of the
> 100*160 mode. It does do the normal text modes, etc. The card appears to
> have video memory in the PC's address space at the conventional CGA
> address. This mode can be disabled by a jumper on the card, so the card
> can co-exist with a real CGA card (and, indeed, with an MDA card, or both
> together, I think).

How advanced did the IBM designs get? are there any added capability
later on?
I also heard that there are 3rd party vendors which designed and sold
their own PGA based solutions.
Who are they?
Also, how practical was a PC/AT or a PC/XT equipped to the card compared
to to similar products at that timeframe in that price range?
In order words, are there better items for cheaper offered on the market
at that time?

> The second mode is the true PGC mode. It gives a 640*480 resolution, 8
> bit colour. The 256 possible colours are selected from a palette of 4096
> (4 bits each for R, G, B for each colour). This mode does _not_ use
> memory-mapped video RAM in the PC's address space, the memory is 'local'
> to the PGC card. The only way to access it is by sending commands to the
> PGCs microprocesosr. There is a communication buffer area at C6000 hex in
> the PC's memory space for about 1K
>
Hmmm...So there's no framebuffer in the card like today's SVGA cards, and
so everything is done via commands through a DMA channel?

> Physcially, the PGC consists of 3 PCBs (processor, emulator, memory).
> These fit into 2 adjacent slots of a PC/XT or PC/AT system. The memory
> card is sandwiched between the processor and emulator and doesn't fit
> into a slot.
>
What is the emulator emulating, exactly?

> There is an 8088 microprocesor, clocking at 8MHz (yes, faster than the
> PC/XT this card could be installed in) on the processor board. It takes
> commands from the PC and sticks the appropriate bit patterns in the video
> memory on the card. There seems to be limited 3D capability in some of
> the commands. Typical commands include drawing lines and arcs, drawing
> polygons and circles, filling areas, printing text and so on.
>
So it's a bit like an S3 Virge 325, which is an SVGA chipset with 2D and
very limited 3D support, but the S3 is VESA 1.2, while the PGA is
very propietory.

Of course, it WOULD be fun to stick a PGA card into an IBM PC/XT and write
a version of some primitive 3D flat shaded game, say, Falcon AT, to take
advantage of PGA...Of course, I predict the game would bring
the PGA to its knees, since I really doubt the ability of the 8-Bit ISA
slot to keep the PGA filled with data.

> >
> > I heard that it is one of the first video adapters with on-board transform
> > capabilities, and that it is very ahead of its time. Can anyone please
>
> It certainly looks to be a fun card :-)
>
Yeah, I would like to think of it as the grand-daddy to the nVidia GeForce
series.
Hmmm...Are there software written especially to take advantage of the PGA?
Received on Mon Apr 23 2001 - 16:28:51 BST