Path: utzoo!attcan!uunet!snorkelwacker!bloom-beacon!hpcvxhp.cv.hp.COM!harry
From: harry@hpcvxhp.cv.hp.COM (Harry Phinney)
Newsgroups: comp.windows.x
Subject: Re: XCopyArea pixmap to pixmap: why is it so slow ?
Message-ID: <8912060116.AA09564@hpcvxhp.HP.COM>
Date: 6 Dec 89 01:16:09 GMT
Sender: root@athena.mit.edu (Wizard A. Root)
Organization: The Internet
Lines: 21

> keith@expo.lcs.mit.edu (Keith Packard)
> Because most benchmarking programs only measure performance for
> on-screen graphics, vendors typically optimize the code/hardware which draws
> there, and leave the off-screen rendering to some first-year engineer.

Hmm, I always thought we optimized the on-screen rendering because it
had the greatest impact on the usability of the system.  Our current
releases will generally render to pixmaps as fast as to the screen,
except in the many cases where the display card hardware provides
assistance (e.g.  rops, blits).


> The disadvantage that this typically has is that special graphics hardware
> is frequently connected to a display memory system that provides additional
> bandwidth (interleaved memory, page-mode access, or wider-than-32-bit access).

One other advantage to a hardware approach is the parallelism that can
be gained by allowing the on-card hardware to run while the CPU starts
dispatching the next request.

Harry Phinney  harry@hp-pcd.cv.hp.com