Subject: Re: PX/PXG and Neon project (beating the dead horse again)
To: Andy Doran , <port-pmax@netbsd.org>
From: Chris Tribo <talon16m@hotmail.com>
List: port-pmax
Date: 04/18/2000 02:13:22
on 4/17/00 8:24 AM, Andy Doran at ad@fionn.sports.gov.uk wrote something
like:

> Toru Nishimura <nisimura@itc.aist-nara.ac.jp> wrote:
> 
>> PXG i860 is driven by passing 'command packet' in reserved RAM area in
>> which both CPU and i860 share.
> 
> Sort of. The PXG also has a PixelStamp. It's possible to drive that directly
> (stamp command packets located in the SRAM), or let the i860 manage it. The
> code that runs on the i860 is loaded by the Xserver at start-up. Otherwise,
> it's inactive. Ultrix makes [part of] the Xserver's address space available
> to the i860 (it's paged in and out of the SRAM).
> 
> The two cards could share an Xserver that ignores the i860. The main
> obstacles that I found are:
>
> - The packet-done interrupts don't get through reliably enough, and on the
> PXG, they don't seem to come through at all (STIC interrupts are routed
> through the co-processor on the PXG). Polling on completion *sucks*
> performance wise.

    Is it possible something isn't being initialized and reset in the proper
sequence? I know this is silly, but could you explain exactly what the STIC
and STAMP are/do?   Performance can come after we get it to a known "happy"
working state :-)

> - I don't understand the format of the two clipping retangles passed in the
> packet. I've tried all sorts of combinations. So, hardware clipping is out
> of the question.
> 
> I have the beginnings of a from-scratch Xserver. I also have a port of
> Xpxpmax. The latter is buggy, and performance *really sucks* (most
> everything is done with a hacked cfb layer and the STAMP_PUTSPANS
> primative).

    Certainly! Remember: A slow X server is far better than NO X server!
Perhaps some guru's on port Alpha might be of assistance, I dunno.

> I am willing to release the source to both if someone wants it.

    Well I've got an PX, and PXG+ here, I'll try to test/feed back/hunt down
documentation on whatever I can.

    Chris

-- 
    
    "I use to be indecisive, now I'm not so sure..."