That's very interesting, Rob. Were the apps compiled using the same
compilers (with the same degree of optimization) in both cases? Were
the time differences actual CPU time of just elapsed time?
Apple's scheduler isn't very good and - particularly in Leopard - some
of their background operations in support of their gimmicky stuff
(like spotlight, quicklook or "time machine") take up valuable cpu
time. I have occasionally thought that Apple deliberately gave these
miserable programs higher priority so that things would run slowly on
single processor G4 and G5 machines, compared to the multicore x86
offerings. Leopard's time machine (back up utility) is the worst - it
brings single core machines to a virtual halt. None of this has been a
problem in my dual core G5 (but is very noticeable on my Powerbook).
Another difference might be the Mach kernel that OS X uses. This
hasn't been talked about much, but there was a time when an OS with a
monolithic kernel allowed things like context switches to take place
much more quickly. Supposedly, the microkernel has been improved, but
it is not clear how much.
Cheers,
wn
On Dec 26, 2009, at 12:28 PM, Rob Sanders wrote:
Warren,
I'd concur. This application was hugely floating point intensive.
Graphics ops were not an issue for us. The app used only low-level
X11 calls (no Motif, or Xt calls even), so what graphics there were
under OSX had to go through Apple's X11 layer before being seen.
Most of the testing I had done was using the XServe as the compute
host, with graphics being redirected to a remote terminal. But I
still consistently saw about a 2x speed improvement when the app ran
on YLD 4 vice OSX 10.3. <sigh> Many fond memories....
-Rob
On Dec 26, 2009, at 3:00 PM, Warren Nagourney wrote:
I think one needs to distinguish between the OS and the CPU. My
experience with the G5 is that its floating point performance is
between 1.5x and 2x as fast as the equivalent x86. Unfortunately,
the fixed point advantages are not there. I use LaTeX a lot and
heard that the typesetting speed improved on Macs (running OS X)
when Apple switched to intel (same TeX source - this might me in
part a reflection on the poorer PPC optimizations in gcc). The
intel advantage might be 20% in LaTeX typesetting (this is a single
data point from a commercial TeX).
On the other hand, the performance of the OS is another matter.
Every linux I have installed on a Mac (or PS3) was much less
responsive than OS X for similar operations. This is a combination
of things like application launching speed and particularly
graphics operations, which are slow in PPC linux since there are no
good PPC drivers for video cards in linux. This is entirely a user
interface issue and a PPC linux server might do very well compared
to the competition (I have no experience with this). Of course, the
speed of apps which don't use graphics should be the same between
linux and OS X since they both use the same compilers.
Cheers,
Warren Nagourney
On Dec 26, 2009, at 8:09 AM, Rob Sanders wrote:
I haven't done much with YDL in some time as I've changed jobs,
but I'd just like to chime in that several years ago that the PPC
Linux's ( YDL for Mac, full RedHat/SuSE on some IBM OpenPower720
hardware) was running rings around the equivalent x86 -or- Alpha
based platforms we were doing some work on. Tried to get my
bosses & customers more interested in it and hit the wall of 'but
it isn't x86'. <sigh>. At the time, a direct comparison of the
*same* base code on a Mac XServe G5 running on YDL4 vice OS X 10.3
had the YDL code twice as fast as the OS X code. Lots of double
precision floating point math, and multiple processes (not
threads) communicating via shared memory. We would routinely max
out any box we were running on.
-Rob
On Dec 25, 2009, at 2:37 PM, Warren Nagourney wrote:
Thanks, Derick.
Although this is a YDL forum, I am afraid to say that there is no
comparison between any linux on PPC and OS X. The former simply
doesn't have the software base that I need. I used to think that
it would be faster than OS X, but after a few installations of
linux on Apple computers, I discovered that OS X wins hands down
in the speed area as well. I think that linux is optimized for
x86 and of course things like flash are only available on x86
linux (I hate flash, but it unfortunately has become a standard
for internet video). There are still some PPC optimizations in OS
X apps and maybe even some Altivec usage (which allows Quicktime
to smoothly run at 1080p on my PPC machines). The tasks involved
in writing my book would have been enormously greater if I had
used linux instead of OS X.
I notice an increasing dominance of ARM in low power portable
devices. This is unfortunate, since ARM simply doesn't have the
computational power that PPC has - I am not sure it even has a
floating point data type. It is too bad that IBM did such a poor
job of promoting PPC; we will need to reinvent the wheel with ARM
when we could have had advanced multi-purpose chips with low
power consumption from the PPC manufacturers (such as PA semi,
which Apple bought and converted to ARM).
Anyway, the improvement in the performance of Apple products
since the switch has been less than stellar, much less than
expected from Moore's law. My 4 year old G5 has a 1.15 GHz memory
bus and an 16x dual layer superdrive, which is very competitive
with the best that Apple can come up with now (for reasonable
prices). It cost much less than a current machine and doesn't
require a several thousand dollar investment in software, which I
would need to make if I use one of Apple's intel superboxes.
Cheers,
Warren Nagourney
On Dec 24, 2009, at 2:28 PM, Derick Centeno wrote:
You may want to know that you may find decent parts for your
system
from http://macsales.com/
I think we may have to really keep our PowerPC running for
longer than
that although I did hear of someone developing a multicore PowerPC
laptop a month or so ago. I've got to search for who this
fellow is
again as I lost track, but I did hear of a fellow who created a
working
Cell based laptop which ran the GameOS and had the OtherOS option.
Pretty neat!
Caveat: If you replace the power supply or other support parts
you
shouldn't have trouble running YDL from it. Be careful
regarding other
components however such as DVD drives: if those go it may be
wiser to
consider an external DVD drive in that situation. I'm unsure if
anyone
we knew remains at Fixstars from TSS; it may not be so easy to
get the
kind of support we became accustomed to. In any case, I'd
advise you
to consider reviewing what notations remain regarding their
advisories
regarding which hardware works with YDL and which do not. As
best I
recall, the past emphasis (by TSS) was to support original Apple
parts.
So the problems to watch for may not be RAM as much as internal
associated devices, such as a newer hard drive or modem or
something
similar. It may be better to just get an HD which resides on a
PCI
card which your system should recognize with no problem as an
external
system; I don't think such a drive would be able to be booted from
within YDL. It would be interesting to try that out as a concept
though.
Anyway enjoy and all the best!!
On Thu, 24 Dec 2009 13:57:49 -0800
Warren Nagourney <[email protected]> wrote:
Thanks, Derick. I still love the PPC architecture and recently
bought an Apple dual core 2.3 GHz G5 for very little money and am
finding it to be absolutely as fast as I could ever hope for. I
will
keep it for the next 3-5 years (assuming I can keep the power
supply
running) and maybe then, the dominance of x86 may have lessened
(it
can't last forever!).
Merry Christmas and Happy 2010,
Warren N
=========
Refranes/Popular sayings:
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There is no evil out of which good cannot blossom.
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