Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!apple!jrg
From: jrg@Apple.COM (John R. Galloway)
Newsgroups: comp.arch
Subject: Re: PMAX/DS3100 frame buffers
Message-ID: <27827@apple.Apple.COM>
Date: 25 Mar 89 04:10:50 GMT
References: <93849@sun.Eng.Sun.COM> <5845@mit-vax.LCS.MIT.EDU> <1989Mar22.175616.1420@utzoo.uucp> <27738@apple.Apple.COM> <111@crltrx.crl.dec.com>
Organization: Galloway Research
Lines: 27

>
>
>It is interesting to note, that with the exception of scrolling, the PMAX
>(DECstation 3100) color frame buffer code ends up outperforming the GPX 
>hardware on uVAXes, sometimes by radical amounts.

Gosh I sure would like to have one of these beasts.

>Also note that most frame buffer operations are WRITES, and not READS, so

Thats interesting.  I would have thought that there would be a lot of
bit blit type activiity (scrolling or window movement, or (with backing store,
or was that save under) expose events) there would be pretty heavy read/write
actions, and then an additional amount of plain writes (new stuff from the
application).  If current systems can completely use up the memory bandwidth
perhaps its time for smart frame buffers that can do multiple concurent bit
blits internally (with out using up external bandwidth unless there is a
conflict), but then if writes really dominate this wouldn't help.  Where did
the data being written come from (i.e. is this a bit blit with X in the middle
or is it really writing new data?)  So whats the next step for more
performance (I assme that there are graphics operations on the 3100 that are
not as fast as you would like??).

apple!jrg	John R. Galloway, Jr.       contract programmer, San Jose, Ca

These are my views, NOT Apple's, I am a GUEST here, not an employee!!