Slow X on IBM RS6000?

[Jonathan Eunice]

Zalman Stern (zs01+ at andrew.cmu.edu) writes... 
 
|  When I was doing development on a 530 (25 Mhz RIOS) I didn't notice these
|  problems. (My MIPS Magnum feels a little better, but at least part of that
|  is the losing X11 performance on the RIOS.)

Leading Tim Bray (tbray at watsol.waterloo.edu) to ask...

|  Very very interesting.  Is it well-established that X on the RS6K is slow?
|  How come?

The currently-shipping AIXwindows is indeed under-optimized.  One
problem is that IBM is shipping X11R3 -- now a moderately old release
-- while other workstation vendors ship X11R4.  R4's better initial
tuning, overhead-saving features like shared widgets, and its greater
maturity are real wins.  Also, I think IBM has had less experience than
HP, DEC, Sun, et al in tuning X.  As it's released from MIT, X is not
the most highly optimized code you've ever seen (no slight intended to
the fine folks who bring us X).  Other vendors had a longer history of
tuning their X packages, and I think that shows too.

The extent of the problem depends seems highly user- and application-
dependent.  I use AIXwindows with 4-7 windows active, and new ones
popping up all the time, and I haven't had much problem running X on a
low-end RS/6000 M320 workstation with 16 MB RAM.  I have not seen any
solid benchmarks that indicate horrid IBM X performance, but I have
heard reports of Island Graphics and (especially) Autodesk software
being noticeably slow -- in the case of Autodesk, absolutely horrid.
One possible explanation I have heard is that IBM tuned its software
for the case of one active window, and ignored the much more common (at
least among workstation users) multi-window scenario.  This is clearly
a brain-dead approach, making the rumor rather more dubious than
usual.  Take it as you will.

I have also heard that IBM Xstations are slow, apparently for much the
same reason AIXwindows is -- X11R3 vs R4, and tuning.  Then again, it
appears that many of the system vendors who've really gone after X
terminals -- HP, IBM, DEC -- have all delivered goods that are slower,
more expensive, heavier, etc than independents like NCD and Visual.
This is beginning to change in the system vendors' second rounds of
product.

NB, though nothing has been announced, it is rumored that IBM will soon
be shipping a much-enhanced X11R4 implementation.  I would expect this
to mean for both AIXwindows and the Xstation.  (Interestingly, this may
show the wisdom of runtime-loaded rather than ROM-based X terminals.
Users of IBM, HP, etc terminals can just replace the X terminal manager
software on one or a few file servers -- no running around changing
tens or hundreds of ROM chips on every terminal.)