Video Upgrade

[Rubywand <rubywand@swbell.net>]

Below are responses on the "Video Upgrade" topic on Sandy's
Upgrade the GS site ... 




      Why don't we take a PC SuperVGA card, and create an interface for
it so it will work with some sort of Alternative Processor Card?

      PC graphics cards= C-H-E-A-P-!-!

      PC graphics cards= H-I-G-H R-E-S-O-L-U-T-I-O-N

      PC graphics cards= Don't *have* to be accessed at the limited
speed of the IIgs video circuits.

      What more could you want? These PC graphics cards are also
time-tested. They don't have nasty bugs like the Second Sight and the
TurboRez cards do

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      Something like this could work. I like the idea of a separate
add-on box which could have slots for cards such as a PC video card.


      SiFan

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      Do you (anyone who reads this) know how PC graphics interfaces
work?

      If anyone can go search for information about them, and then post
the URL's here on the message board, it would be great! 

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      Interfacing a PC graphics card to the IIGS wouldn't exactly be
easy, it might be easier to redesign such a card WITH chips from a PC
graphics card.

      Why? because PC graphics cards from the EGA standard upward had a
BIOS imbedded on the card which extends the PC's bios and is most
probably in 8086 assembly. This is to allow special hardware specific
stuff to be handled by software in the BIOS.

      Assuming we don't use this, and assuming standard vanilla VGA
hardware, we could probably write on the card's on-board video-memory to
view vga or svga style graphics. Drawbacks to this is the II's original
text, lo/hi/super res graphics will not come out on the PC monitor.

      We might also design circuitry to independently mirror this info
on the card so that everything will still work, but I think such a card
already exists. 

      Jon 

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      Assuming that we are talking about a separate box (with PCI, ISA,
newGS Slots) connected to the current GS and to a modern display
monitor, a reasonable user concern will be that all current GS displays
are available without the need to retain the old display monitor.

      Evidently, this will require converting GS video for display on
the new monitor and inserting relays at the box's Video output to allow
switching between the converted 'old-GS' video and video from whatever
new card/circuit is employed.

      This implies that an in-GS Video Converter Card might be a good
first step in the upgrade. That is, the VCC and new monitor would be a
standalone add-on for the current GS which would, eventually, make it
possible to connect to an external box with the advanced video card and
other major upgrade features.

      Rubywand

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> Hey, why not write the equivalent of 8086 code in 65816? Or if we go
> the ARM processor upgrade route, an ARM chip should be able to deal with
> a Super VGA card, correct?

It would have to be a very specific chipset. My research (on the web)
has gotten nowhere... or just got to show me that modern (recent) Super
VGA chipsets like the S3 require some sort of hardware developer license
for them to release pinouts and chipset information. In the book I have
(peter norton's inside the IBM PC & PS/2), a real old one at that, it
only shows how to access the VGA cards from software in the BIOS...
meaning we have to agree on what chipset to use and stick to it. We also
need pinouts and info on the chipset. With this... we could imbed an
onboard microcontroller that "listens" in on the //GS bus for graphics
specificm emory access.

>
>
> I think it would be good to go with an ARM accelerator card, and an
> expansion box which sits outside the computer. This box could hold PC
> cards (graphics, ethernet)
>
> Then, the ARM chip (emulating the 65816 through software) could EMULATE
> the GS screens (graphics, text) through software!!!!

and output it on the VGA card.. we will either use a PC's VGA card and
have an ARM I/O controller handle the video... what I'm not sure is, if
PC video cards are "generic" enough to be handled this way, or we might
have to stick to just one card. My guess is if we are going for the
"works with a lot of vga cards" approach, we'll have to imbed some form
of 8086 processor in the system... (not my type for emulation purposes)

>
>
> Software is alot easier to deal with than hardware is. We need to make
> a basic Accelerator card for the IIgs (One that is so fast, Hardware can
> be emulated using the fast performanc of the processor)
>
> There is already source code available to emulate the Apple II screens
> (tons of apple II emulators!) This code is written for PC super VGA
> cards! If we have a fast processor, many of the things that were
> hard/expensive to create in hardware become easily developed through
> software (which has already been written)
>
> What do you think about an ARM processor controlling a PC superVGA
> card? This is one area you seem to know alot about. Is it possible to
> control a PC card with an ARM processor? Is there software that will
> already do this?

it could be done. but there is no software yet to do this, the ARM
processor is mostly used on imbedded microcontrollers... not desktop
PC's (to my knowledge) we could have a card plugged into a slot on a GS
to "listen" to video memory access (soft switches, writes to memory) and
have the card emulate GS style graphics, outputted to PC SVGA monitors
(this should solve the rare NTSC-frequency monitors problem) and we
could add more switches to turn on even higher resolutions.

Jon



 
Rubywand