[x264-devel] Tilera Gx36: current state?

[Jason Garrett-Glaser]

On Sun, Jan 13, 2013 at 4:23 AM, Max Lapshin <max.lapshin at gmail.com> wrote:
> Hi.
>
> I've seen necrothread on ycombinator where Jason wan't amused about Tilera
> multicore chip.
>
> What is current state of this board:
> http://www.tilera.com/sites/default/files/productbriefs/TILEncore-Gx36_PB028-02.pdf
> in terms of launching libx264 there?

I haven't heard of anyone even trying it as far as I know, but I'd
love to see actual results if someone has a chance to!

> Can one core of such device encode 720x576 25 fps tv channel?

Well, let's do some math.  With one core and all assembly disabled
(SIMD off, since last I recall the Tilera doesn't have SIMD), a 3.4Ghz
Core i7 can get about 90fps at 720x576 on preset superfast.  That's
about 26-27fps if you scale down to 1.2ghz.

So, if each core of the Tilera was as fast clock-for-clock as a state
of the art Intel CPU and had no problems with memory bandwidth or the
like, it could (just barely) do that.  But I'd be shocked if it was
even within a factor of 2 of the Core i7; competing with Intel on
per-cycle performance is incredibly difficult.

If they've added SIMD since it might be easier, but you'd still have
to write basically all the assembly code, which would be an enormous
amount of work.

Of course this is all guesswork; actual benchmarks are welcome!

Jason