Watch Impress PS3 Technical article, from GDC (some new info)

Which is why it's annoying because there shouldn't be a need for assumptions when you can just say 24 PS and 8 VS units!

 

to me, this is good news. I means that ps3 wont be as expensive. One thing is questionable, whats up with all of those transistor?

 

Wont be as expensive? How do you figure that one out. The GPU is going to be the same size as they announced at E3 >300M transistors @ 90nm. G70-deriviative is not 'cheap' or 'underpowered'. Personally I'm very happy, and curious what changes they've made to label it 'based on'.

 

I didn't say that. I said "as expensive" as believed.

 

I know! Some believe it's because of the ps2 emulation. Anyway i meant since it's not based on new tech, it should be cheaper. But 300M transistors raises questions.

 

Indeed, which was pretty much what I called you out on

In terms of them actually paying nVidia to design it, it would be cheaper than starting from scratch, its reportedly not dissimilar to what MS paid ATi (according to SCB at GAF). But that doesn't translate to a less expensive pricetag at the end of the day because its relatively small.
I don't think PS2 is being emulated, Kuturagi's comments pretty well confirmed that PS2-on-a-chip will be integrated in some way.

 

I always assumed they were basing it on G70 at the time (E3) which was 302 million transistors. Nothing more too it.

Since then G71 has been slightly re-jiggered and weighs in at 278 million transistors though.

 

The whole thing...or just latter half of it?

 

That paragraph describes differences between PPX and PPE, that's where 128 registers come from, there's no mention of any upgrades.
It'd be a pretty damn useless upgrade anyway, not to mention there's no marketing angle to it either.

Me too, cuz I was laughing too hard at a certain summary slide to post.

 

Is it true an entire SPE is dedicated to the OS when MS only asks for what 5% of two cores resources on Xenon?

Is that right? That OS sure seems hungry...hope it's doing a whole lot.

Maybe another stupid question but why wouldn't the OS be put on the PPE...because I thought...only the PPE had the HW support for interrupts and permissions most modern OSs require/use?

 

Does anyone have any details on how expensive a branch miss on a SPE is?

 

I think it's 18 cycles.

 

That's correct, it's the part where Zenji Nishikawa compares PX (Xbox 360 CPU) and PPE... SCE recommend using SMT on PPE in as many cases as possible by splitting data sets in 2 as it's faster by hiding latency/stall and utilizing L1 effectively. It's what I found interesting as the GDC presentation by Microsoft suggests SMT threads on PX suck apparently and using a full core for 1 thread is more efficient.

6 SPE are usable from apps, 1 SPE is for OS/system which coincides with what Nikkei reported on what Kutaragi said in the last year.

The article says RSX is NV47-based, with 24 PS and 24 texture units. FWIW Nishikawa speculates that as it's G70-based (not G71) it doesn't have AA on FP render target.

I suppose some parts of the OS are still on PPE but background services such as networking and media-intensive services such as video camera processing require 1 SPE for its rich media perf and security.

 

The presentations I saw from MS said use 1 "intensive" thread and 1 not-so-intensive thread (ie, I/O) per core...

 

Umm, maybe cause if it was based on NVIDIA's bleeding edge cards like MANY people were speculating i.e. g80, it would have much lower yields and a higher cost?

I think if you were worried about price, and actually thought that RSX was gonna be based on g80(which most people knew was fantasy) then this is good news, it makes it that much more likely they might be able to hit that $399 pricepoint. If you were worried about price...

 

Humm... 6 SPEs instead of 7. A 1 year old GPU wiyh half the bus of its PC counterparts and probably fewer Rops to fight against the Xenos. It seems the PS3 is less powerful than expected
I am not trying to downplay...But the reality hits this time.
So the consoles might be equal when it comes to graphics, with the 360 shining later on...
It's up to developpers to decide who wins the race !

 

Maybe you are correct though from
http://download.microsoft.com/downl...ab-df6c7a2580b9/Coding_for_Multiple_Cores.ppt
I thought they suggest some cores with single (intensive) threads and the other cores with multiple threads, by looking at the actual game examples (Kameo, PGR3) and advise devs to be cautious of SMT. OTOH, what SCE apparently suggests is PPE inherently sucks because of its in-order-ness and higher latency gap with main memory, so programmers have to utilize it cleverly to get reasonable performance.

 

Right, you still only have one set of resources on PX or PPE, so SMT with two heavy threads might be counter-productive. Really well scheduled code will minimize the amount of work that can be done in a second thread for "free". If another thread is causing a timing critical thread to stall then you're going to have problems. I assume that was why PGR3 had to (IIRC) assign one PPE to just audio, but that seems like a pretty expensive design decision.

With Cell you have 6 SPUs to assign heavy work threads to so it's probably not as critical to maximize single-thread performance. Well, as long as you can refactor your code to work within the SPUs footprint.

 

Has anyone any information on whether the PS3 OS is also using some resources on the PPE as well?

And how about this crazy idea, since they only mention the pixel shaders of the RSX, could it be that the Cell will be doing all the vertex work? As for the transistor count of RSX, with the VS removed one would think that the number of trannies would go down, but what if they added silicon to be used for the backward compatibility of PS3?...

 

That's crazy, as they already said RSX has separate shaders which is it doesn't make sense without PS AND VS.