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From: allen@basalt.uucp (Allen Akin)
Newsgroups: comp.sys.dec
Subject: Re: X performance on DEC5000
Message-ID: <1990Oct16.033743.4246@wrl.dec.com>
Date: 16 Oct 90 03:37:43 GMT
References: <5239@mit-caf.MIT.EDU>
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Reply-To: allen@atd.dec.com (Allen Akin)
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Organization: DIGITAL Advanced Technology Development, Palo Alto, CA
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In article <5239@mit-caf.MIT.EDU> rajeev@caf.mit.edu writes:
>Does anyone out there know how the X performance of a DEC 5000/200CX
>compares with a 5000/200PX?

In general, the PX is *much* faster (2-3X) for vectors, polygons,
XCopyArea, and filled primitives where the fill-style meets certain
requirements (solid, or stipple or bitonal tile with sizes equal to a
power-of-two less than or equal to 16).  The CX is faster for image
display (XPutImage) and for very small primitives whose drawing time
is dominated by server overhead.  Otherwise they're about the same.

A summary comparison of the two options is available by anonymous ftp
from decwrl.dec.com.  Check out the file pub/DEC/ds5000.graphics.ps.Z.
If you don't have ftp access, let me know and I'll mail you the
PostScript (about 88KB).

>... does the X server take advantage of this hardware?

Yes.

>                                           ... Is there any hardware
>in the PX that is designed specifically with X performance in mind, or
>does the PX address other graphics API's, e.g. PHIGS?

Although the PX was certainly designed with X in mind, it was also
influenced significantly by PHIGS and PEX.

The version of PHIGS that's currently available on the PX uses X11
requests for drawing, so it takes advantage of the graphics accelerator
in that way.  No comment on future versions that may use the PixelStamp
for more sophisticated drawing operations not supported by X. :-)

>On a related note, how does the X performance of the 3D systems (the
>PXG and PXG-turbo) compare to the 2D systems?  Did DEC make sacrifices
>in X performance in order to speed up the 3D cases?

The PXG is almost identical in performance to the PX for 2D
operations.  They both use the same speed PixelStamp chipset and video
RAMS.

The PXG Turbo varies from essentially the same speed as the PX to more
than 2X faster, depending on the 2D operation you choose.  The Turbo
uses faster PixelStamps and two rendering chips instead of one, so
large-area operations more then double in speed.

Allen Akin
Advanced Technology Development Group
Digital Equipment Corporation