[mythtv-users] mythtv on the ps3

Jeff Breadner jeff at breadner.ca
Fri Jan 12 19:46:25 UTC 2007

On Fri, 2007-01-12 at 14:01 -0500, Jeff volckaert wrote:

> Could you also post on the performance of the PS3 as a linux computer?
>  How many cores show up?  How fast does it compile stuff?  With up to
> eight 3.2Ghz cores that thing should rock like a mini-mainframe.  You
> should be able to do eight transcodes at a time.

Actually, Linux on PS3 performance is still pretty disappointing. 

It looks like a dual-core PPC at 3.2GHz, but it feels a lot slower than
that would imply.  It feels more like a 2GHz P4 or so.  The most useful
explanation I've found as to how performance on this machine stacks up
is at this article on pages 2 and 3:
http://dpad.gotfrag.com/portal/story/35372/?spage=1  The main thing I'm
after here is that this machine has a narrow in-order execution core,
which is much less efficient at doing general computing work than the
wider, out-of-order execution cores that desktops generally have.

There is kernel support for the PS3 in that the thing will run, but
there is a lot of work that remains to get cell support into utilities
that can use them; until that happens, the PS3 will continue to behave
like a mid-range Mac.

There is a LOT of potential in this machine, but there needs to be a lot
of work done by core GNU/Linux developers in order to properly unleash
this, everything needs to be rewritten in a big way to incorporate good
cell support, from how I understand things (and I'm no expert at this by
any means).  Until things like ffmpeg are reprogrammed to take advantage
of the CBE, each instance of ffmpeg will actually run on the main cell
that behaves as the dual-core PPC, so there won't be any speedup at all
when using PS3 over a regular PPC core (and it might actually be slower
because of the in-order execution thing and lack of RAM).  The extra
cell processors will continue to go unused.  This isn't just changing a
compiler or something, there are core differences in programming that
have to be implemented.

Compiling takes a lot of time; compiling mythtv-0.20-fixes took 2 or 3
hours last night (I didn't notice exactly when it finished).  I used
make -j2.

But, my family was getting frustrated with how laggy our XBox frontend
seemed, and it looks like the MythTV UI will be a LOT snappier when
running on the PS3.  We just have to figure out how to get the video to
display properly, hopefully we can get that working OK without access to
accelerated video.


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