*Sigh* The Inquirer Strikes Again: RSX "Slightly Less Powerful" than 7800

[onanie]

It beats me why Sony/NVidia decided to handicap RSX with a 128-bit bus, but there it is. A cost-saving measure.

Of course, on the Xenos, the 128 bit interface is called a design feature.

 

[Titanio]

The CPU link is not going to make the blindest bit of difference to texturing or rendering into the framebuffer - the two most demanding bandwidth consumers in a GPU.

I'm not talking about memory bandwidth. I'm simply talking about CPU-GPU bandwidth. G70's is a small fraction of RSX's.

It's a seperate point from the one I was making but it is debateable how that bandwidth may or may not be used to pull or push things to/from RSX to XDR. I'm sceptical enough about framebuffers myself, but textures etc..

It beats me why Sony/NVidia decided to handicap RSX with a 128-bit bus, but there it is. A cost-saving measure.

I think we can forgive Sony the few they've made compared to others, eh?

 

[Jawed]

Well, when the backbuffer has its own private 32GB/s bus, the 128-bit bus to main memory has got the bonus of not trying to support the 32GB/s consumed by backbuffer operations, in favour of texturing and keeping the CPU happy.
Sounds like a good deal to me.

But then we weren't comparing RSX and Xenos, we were comparing RSX and G70. Sigh.

Jawed

 

[onanie]

Well, when the backbuffer has its own private 32GB/s bus, the 128-bit bus to main memory has got the bonus of not trying to support the 32GB/s consumed by backbuffer operations, in favour of texturing and keeping the CPU happy.
Sounds like a good deal to me.

But then we weren't comparing RSX and Xenos, we were comparing RSX and G70. Sigh.

Jawed

Bonus of course, that xenos also has to share the 128 bit interface with the CPU. The comparison is necessary to put your comments back in the right perspective. I hope you understand.

 

[Jawed]

I don't doubt that procedural textures and vast swathes of high-poly geometry (potentially "pre-shaded", including operations analogous to vertex texturing) by Cell will be key features in PS3.

But the point stands that these are techniques to compensate for the somewhat constrained implementation of the GPU.

If Sony/NVidia can engineer Cg so that it runs on both Cell and RSX (say vertex shaders on both, pixel shaders solely on RSX) then it's going to be very interesting - no doubt about it. A great way to use some "spare" GFLOPs in Cell.

But as a GPU RSX in its own right is badly hampered by such a low bandwidth to its memory.

Jawed

 

[Jawed]

Bonus of course, that xenos also has to share the 128 bit interface with the CPU. The comparison is necessary to put your comments back in the right context. I hope you understand.

Well if you read what you replied to, you would see that I mentioned the CPU bandwidth - as a matter of comparison, high-end PC games are quite happy with 4GB/s of CPU bandwidth.

The fact still stands that if Xenos needs 32GB/s to its backbuffer, the same visuals at the same resolution will entirely swamp RSX. It literally cannot do the same visuals because it doesn't have access to a backbuffer at 32GB/s.

The concensus would appear to be that PS3 games won't make use of MSAA in order to meet RSX's bandwidth constraints.

This is all water under the bridge, stuff that's been agreed upon for ages round here.

Jawed

 

[onanie]

Well if you read what you replied to, you would see that I mentioned the CPU bandwidth - as a matter of comparison, high-end PC games are quite happy with 4GB/s of CPU bandwidth.

The fact still stands that if Xenos needs 32GB/s to its backbuffer, the same visuals at the same resolution will entirely swamp RSX. It literally cannot do the same visuals because it doesn't have access to a framebuffer at 32GB/s.

The concensus would appear to be that PS3 games won't make use of MSAA in order to meet RSX's bandwidth constraints.

This is all water under the bridge, stuff that's been agreed upon for ages round here.

Jawed

Concensus, it is not.

 

[3roxor]

It seems to me the Inquirer is in favour of ATI. They hyped the R520 more than Ati themselves(hardly possible but they did..) We will know the thruth soon.

 

[Titanio]

The fact still stands that if Xenos needs 32GB/s to its backbuffer, the same visuals at the same resolution will entirely swamp RSX. It literally cannot do the same visuals because it doesn't have access to a framebuffer at 32GB/s.

We can start examining scenarios where Xenos is quite bandwidth limited for things other than framebuffer ops relative to PS3 too, you know. 11GB/s of read bandwidth between the CPU and just texturing even, may not be very much. How much bandwidth will RSX need to use for the framebuffer before it has less read bandwidth left over (for texturing) than Xenos? Not every game's framebuffer is going to need or want the bandwidth on the daughter die either, and such games may have been better off with more bandwidth to "system memory".

One begins to wonder about MS's warmth towards procedural tricks..afterall, the less the CPU takes in, the less likely it is X360 will be starved of read bandwidth for ex-framebuffer ops (texturing).

 

[swaaye]

It is somewhat surprising to me that they would opt to use a 128-bit bus for such a critical area. It must be a lot cheaper for them to go that route.... That makes the bandwidth sorta like a 6600GT I'd imagine. I doubt they'll use some ultra-high-tech high clock DDR3 that surpasses 6600GT's chips that much...

I have to say that Xenos just feels to be a much more interesting GPU, one that is just very tailored for console needs.....

I'm not overly familiar with RSX though. Does it have any significant fast local dram like Xenos? Or is it believed to be basically the same as G70?

 

[Carl B]

The truth is not much is known about RSX at this point, save that it is derived from the same architecture as G70. That is not to say derived from G70 itself, as development was concurrent and remains ongoing. There should clearly be similarities though.

We'll see what the deal is soon enough. It may end up being essentially a GTX thrown in a console when it's unveiled, but until then I think the chip should be given a little benefit of the doubt. There is too much discussion carried out with the tone of 'fact' when in reality we don't know the deal yet.

 

[Jawed]

You've heard of the effective doubling of the bandwidth twixt CPU and GPU in XB360 with custom compressed graphics data formats? Very handy. Effectively 40GB/s for all graphics data in both directions.

Have you seen what happens to performance when you have a 128-bit bus running at 1050MHz effective rate trying to do AA and AF:

http://www.beyond3d.com/reviews/bfg/6600gtoc/index.php?p=10

I picked a kind example there - a game that's essentially CPU/shader-limited, not bandwidth limited. Still AA/AF kick in with a big bandwidth hit.

6600GT only has 4 ROPs because any more would simply be overkill for its bandwidth.

Jawed

 

[Azrael]

Any news that is the least bit negative toward the PS3 really puts the spot light on the ******s around here. Just accept that the RSX may not be as powerful as Sony's marketing hype and some ****** wishful thinking makes it out to be.

 

[talyn99]

scooby_dooby
Junior Member


Join Date: May 2005
Posts: 753


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i think the quote might be on the DVD with PSM.

Someone started a thread at another forum called "the dumbest thing i've seen in PSM", he doesn't seem to be aware of the inquirer article.

he writes this:

"yea i got psm today with the dvd... i put it in and watched the "Luna" tech demo that nvidia showed at the E3 press conference with the woman and the creatures.

they said somthing about the graphics chip NVIDIA Ge Force 7800 that kinda pissed me off... " ThePS3 graphics chip will almost be indentical, only slightly less powerful" "

Anyone have PSM? Watched the DVD?






Yes, i have the DVD, and it DOES says that. I must admit, it had me scratching my head. I do not post alot, but I do keep up with what you guys have to say, and RSX info. Im guessing someone made a boo boo.
peace

 

[Carl B]

Azrael I think everyone's ready to 'accept' it. At the same time, that doesn't mean that it should be viewed as a foregone conclusion, am I right?

 

[Vince]

Is it realistic to expect the RSX to ship at 550MHZ?

Yes. Sony will likely fabricate the RSX on their CMOS4 process, which is quite mature having been in production with the EE+GS and PSP ICs since late 2003. Overall, I'd assume their 90nm, 2-stack low-K process is a bit better than TSMC's comparable 90nm offering, and quite a bit better (understatement) than TSMCs bulk 110nm process which lacks any dielectric. TSMC, and founderies in general, really aren't comparable to semiconductor companies like Intel, IBM, AMD, or Sony.

 

[Azrael]

Azrael I think everyone's ready to 'accept' it. At the same time, that doesn't mean that it should be viewed as a foregone conclusion, am I right?

You are right. I was just commenting on what seems to be a huge defensive backlash by certian people toward news that could easily be true. The RSX, although it may run at a faster clock speed than the 7800, may still not be as powerful. It could have fewer pipes which allows it to run at the higher clock speed, for instance. I just think that the topic deserves serious discussion, not fan boy damage control.

 

[Azrael]

My take on the issue is this: Sony has been awful quiet about the RSX, and while some take this to be a sign of the sekret power of the PS3, I take it as a sign of just the opposite. It is logical to believe the the RSX is not going to be the equal of it's PC counterpart because of sheer cost restraints. Like the NV2A in the Xbox, it is going to have to be crippled in some form to keep that cost practical enough for a console.

 

[BlueTsunami]

You are right. I was just commenting on what seems to be a huge defensive backlash by certian people toward news that could easily be true. The RSX, although it may run at a faster clock speed than the 7800, may still not be as powerful. It could have fewer pipes which allows it to run at the higher clock speed, for instance. I just think that the topic deserves serious discussion, not fan boy damage control.

I never understood the "my console is more powerful than your console" type of arguments...funny seeing Playstation fans (Which i'm one also) trying to stick it to Xbox fans saying the PS3 will be technologically better than the 360...also seeing the same said Xbox fans saying its all about the games. Its good to know whats inside....but what else can be said?...where yet to see the PS3 and 360 at its full potential...and reaching the full potential of a console is up to the Developers....so its pretty much pointless..

As far as this Inquirer thing....we can all see where they get their sources from ....but they have the fricken devils luck!

 

[pjbliverpool]

Its possible that the quote was referring to the 7800 Ultra rather than the GTX. Maybe the 7800U runs faster than 550Mhz?