Personal thoughts…

Tech, Hockey, and random thoughts…

Console examination #1

The Xbox360 is an odd dichotomy between technically impressive and underwhelming.

3x PowerPC cores at 3.2GHz, each with SMT ensures it's a heavily threaded architecture.
But each core is a heavily cut down version of the G5 with all 3 cores are not capable of OOE (Out of Order execution), and are only dual issue it's IPC isn't going to be very good at all. The G5 in comparison is a 5-way OOO (4 instructions + 1 branch more specifically), peaking currently at 2x 2.7GHz.
Microsoft isn't going to openly state that however, but a little judicious examination of the specifications, and IBM's comments reveals much.

The graphics processor carries is similar…. based off the R600 with unified Pixel/Vertex shaders, and 12 pipelines with 4 ALU's per/pipe @ 500MHz it should offer shader performance a decent margin above that of the X850XT PE.
Yet with only 8 Raster Ops (ROPS) it's pixel throughput is only very marginally better then current mainstream PC graphics cards and well below the X850XT PE. The GF 6600GT in fact, can offer stencil fillrate comparable to the XBox GPU, and nVidia's high end cards nearly twice as powerful in that respect.
With Microsoft pushing High Definition TV's so heavily it seems counterproductive to design the graphics core for ~4000 MP/s fill rate.

I'm betting that the HiDef angle is primarily marketing, and the actual games while HiDef capable probably won't be much better then current non-Hi Def XBox visuals. Most Xbox 360 games will probably still be aimed primarily to those without HiDefinition capable TV's.

Bizarre, in some respects it looks quite nice for a late 05 launch… in others it seems decidedly weak for a console that should be expected to last 5-6yrs.
Long term we shall see out it works out for them.

An interesting route to take. It certainly won't be very programmer friendly, I wonder what the underlying OS is?
The Xbox used a Windows CE derivative on the Coppermine Celeron/PIII dirivative, with the Xbox360 going PPC it certainly won't be any variant of Windows.

With Sony's Cell processor in the Playstation 3 being a massively parallel processor with many small relatively fixed purpose cores buffered by one larger more powerful core it'll be heading the route of many many threads but each thread/core being relatively limited in it's capabilities and comparatively slow. The PS3 will certainly be an extremely difficult console to get good performance out of and optimize code for, even without taking into account how difficult it will be to program for. Still, under the right conditions is could potentially be vastly superior to the XBox.
Unfortunately I don't see the Cell doing well, ironically it's a little too good in some respects… it's too far ahead of it's time. With the Cell built on a 90nm process, each of it's many cores has had to be dumbed down and stripped of most of it's general purpose nature in order to get a reasonably cost effective die size.
Too much, too soon.
Long term, I think Sony has the right idea… but not until lithography tools can handle a 32nm process at the very least. At such a process size the massively parallel route of the Cell may work out very nicely as each individual core could be similar or close in complexity to modern single-threaded processors. and wouldn't need to be so excessively dumbed down as they are in the Cell.
(The Cell implemented in the PS3 appears to be 1x 3.2GHz PPC + 7x SPE @ 3.2GHz)

Nintendo's Revolution of course we know little about it's specifications beyond the fact that it's some sort of PPC derivative, utilizing a ATi graphics.

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May 15, 2005 - Posted by | Console Examination

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