Gayle PCMCIA Addressing Questions

[bubba]

I've been working on my driver for the HP PCMCIA VGA card and have encountered one poetential design issue.  As you know, the amiga only maps 4MB of the full 64MB PCMCIA common memory address range.   The HP cards mimics a ISA SVGA card and provides the vanliia VGA banked memory buffers at offseet address 0xA0000  or 0xB0000.  These are within gayle's address range.  As the card has a SVGA chip set, it also provides a linear framebuffer at 0xe00000.  Alas, this is out of galye's address range.  

I'd much rather use the linear framebuffer as writing banked switch VGA code is convoluted and requires a lot of CPU.   I'm not familiar with the gayle chip, but is there anyway to force it to map a different section of the PCMCIA common memory into it's 4MB address space?    

If it can't be don't in software, would it be possible to develop an external adapter to do bank switching?  Conceptually this would be simple:  overload one of the PCMCIA I/O registers as a bank select register and create a PCMCIA adapter board to do the address translation.  I'm not a hardware guy, but it seems this would be a trivial component to develop.

Thanks
-bubba

[ncafferkey]

Are you sure there's no way to change the location of the framebuffer? For instance, PCMCIA cards usually have multiple configurations available for use that usually use different addresses.

[bubba]

Unfortunately, I don't have any documentation for the PCMCIA card.  I am using  the XFree86 source code developed for the HP iPAQ as my only technical reference.   The code uses the e00000 or a0000 addresses for accessing the VGA video ram.   I did try to find if the Trident VGA controller in the card supports some type of address translation for the video ram, but I had no luck.

Since I'm just doing a proof on concept right now, I'll deal with the limits of using the banked memory just to get a feel for how well it performs with the Amiga.  I've already written a basic test harness for the card and will try to test it once I get my cards from China.


-bubba

[ncafferkey]

Not having the docs for the graphics chipset eliminates one possibility for changing the address, but I was referring to changing it via PCMCIA configuration. This is part of the PCMCIA standard and is well documented.

The addresses used for the various configurations can be extracted from the card's CIS. The easiest way to do this would be to use the Linux PCMCIA tools on a laptop, but if you want to do it on the Amiga, my pccard.library would be useful. You might also want to look at how Linux configures this card at the PCMCIA level if you haven't already.