News about Rambus and the PS3

[Panajev2001a]

I bet that main RAM in PSOne is not faster than 400 MB/s whcih is 8x slower than the 3.2 GB/s main RAM PlayStation 2 uses...

3.2 GB/s * 8 = 25.6 GB/s... I think it should not be economically prohibitive and surely thr PlayStation 3 Hardware designers will find a way of using that bandwidth...

For the CPU and GPU they can keep the e-DRAM path as it will provide a very good amount of bandwidth... the current GS has 48 GB/s and for Cell we seem to be talking about 1,024 bits for combined data bus width as far as the e-DRAM is concerned.

Yes, this is less than the combined 2,560 bits bus the GS has, but I expect the clock-speed of the CPU and GPU to be quite higher than 150 MHz too

 

[MfA]

Differential signalling Panajev

25.6 GB/s = 64 bits = 128 datapins

 

[Panajev2001a]

Oh darn... hehe I forgot about that part

Thanks Marco for correcting me

 

[jvd]

Yellowstone would be used as main RAM not as VRAM... the CPU ( Cell seems to use e-DRAM to support its massively parallel architecture ) and GPU would have e-DRAM which would probably not be Yellowstone, but custom e-DRAM by Sony, IBM and Toshiba.

still don't see why they need the speed for system ram. Oh well guess time will tell .

e-DRAM travelling at 60-100 GB/s cannot be fed fast enough from a 4.2 GB/s memory sub-system, unless you plan to have tons of e-DRAM on the chips which is not really likely IMHO...

25.6 GB/s would be economically feasible as far as main RAM is concerned and would allow to keep e-DRAM on the CPU and GPU lower than 64 MB if needed.

PlayStation 3 will be dealing with MASSIVE data streams and main memory cannot be such a big bottleneck to achieve maximum system performance...

i would see 20gigs as enough. if they even need that much. mabye a dual controller like the nforce series would be better. 64 megs on each controller.

 

[Panajev2001a]

25.6 GB/s comes in the package with a standard 64 bits controller and 3.2 GHz signalling... nice and IMHO economically viable

 

[randycat99]

still don't see why they need the speed for system ram. Oh well guess time will tell .

When we get to the realm where local memory reaches or even exceeds performance of a fast L2 cache of today such as that which is being suggested in these upcoming memory architectures (except this time packing 1000x-ish the data capacity as an L2 of today), then we will see the true optimal performance of these fancy computational processors (essentially an entire game process running in L2). None of this "blazing fast for a 100 msec, then a speed collapse as the uber processor struggles to suck new data through a very thin straw". The days of the "traditional" PC architecture for high-performance applications are quickly becoming numbered.

 

[Grall]

i would see 20gigs as enough. if they even need that much. mabye a dual controller like the nforce series would be better. 64 megs on each controller.

I don't know what you guys are thinking with here in this thread... First of all, PS3 main RAM cannot be compared to PC main RAM, because the two systems are fundamentally different. PS2/3 main RAM serves as primary texture/geometry storage AS WELL as program/data storage, a role which on-board graphics RAM serves in a PC. As we're ALREADY B/W-limited in some situations on today's 20+GB/s graphics cards, think of what will happen in a PS3 with unknown (and massively increased) graphics rendering performance even WITHOUT adding in the needs of a possible near-1TFlops/s Cell processor also into the mix. Even assuming both GPU and CPU have 64MB of on-chip DRAM, that is still not nearly enough to keep both functioning at peak efficiency if main RAM bandwidth is a measily 25GB/s split between both processors.

We have hardware with MORE than 25GB/s TODAY set aside for GRAPHICS USE ALONE. In 2 years, 25GB will be old hat. 2 years ago (ca), the GF3 was still impressive with its 7.2GB/s. How fast is that today? Positively SNAIL-LIKE, that's what! VISION, PEOPLE! VISION! As in, "you guys lack it"!

The PS3 would be massively unbalanced with tremendous theoretical peak performance mostly unrealized due to the thing being starved of bandwidth. Think GF2 GTS on a truckload of steroids.

You guys look at tomorrow with the realities of today in mind. Remember, this thing will not be on sale for like another TWO YEARS, that's a long time in this business. 128-bit (256 pins with diff signalling), 400 true MHz bus will most likely not be out of reach then. Remember, Sony will want to stick just one device per memory channel like in PS2 and solder it straight to the mobo instead of have it sitting on a separate piece of board through a connector, this fixes a lot of timing issues that only appears when daisy-chaining devices on a memory stick. Also remember, we know Sony will initially take it on the chin profit-wise when it comes to the hardware and SMILE. So what if each machine costs a small fortune to build, they're out to win the war, not the battle...

You guys lack vision. Heinlein wrote sci-fi fiction where people used slide rules in space because he couldn't envision the advent of a little simple thing called the pocket calculator (or desktop PC for that matter). You're like him, you worry over CURRENT problems and apply them to tech that isn't set to appear until the middle of the bloody decade!


*G*

 

[jvd]

I have tons of vision... mostly used for looking at the ladys

 

[nonamer]

Speaking of fast RAM, GDDR-3 can already provide 51.2 GB/s now: 800Mhz * 2 (DDR) * 256 bits / 8 (bits/byte) = 51.2 GB/s.

 

[Psychogenics]

Speaking of fast RAM, GDDR-3 can already provide 51.2 GB/s now: 800Mhz * 2 (DDR) * 256 bits / 8 (bits/byte) = 512 GB/s.

Wow sounds expensive....more expensive than XDR.

 

[MfA]

Sucks a lot more power though, but yeah ... in essence GDDR-3 has the same per pin bandwith as XDR.

 

[megadrive0088]

main memory on

PS1 is around 130+ MB/sec IIRC

Nintendo64 is 500 MB/sec

M2 was well over 500 MB/sec

Dreamcast 800 MB/sec

I don't know what you guys are thinking with here in this thread... First of all, PS3 main RAM cannot be compared to PC main RAM, because the two systems are fundamentally different. PS2/3 main RAM serves as primary texture/geometry storage AS WELL as program/data storage, a role which on-board graphics RAM serves in a PC. As we're ALREADY B/W-limited in some situations on today's 20+GB/s graphics cards, think of what will happen in a PS3 with unknown (and massively increased) graphics rendering performance even WITHOUT adding in the needs of a possible near-1TFlops/s Cell processor also into the mix. Even assuming both GPU and CPU have 64MB of on-chip DRAM, that is still not nearly enough to keep both functioning at peak efficiency if main RAM bandwidth is a measily 25GB/s split between both processors.

We have hardware with MORE than 25GB/s TODAY set aside for GRAPHICS USE ALONE. In 2 years, 25GB will be old hat. 2 years ago (ca), the GF3 was still impressive with its 7.2GB/s. How fast is that today? Positively SNAIL-LIKE, that's what! VISION, PEOPLE! VISION! As in, "you guys lack it"!

The PS3 would be massively unbalanced with tremendous theoretical peak performance mostly unrealized due to the thing being starved of bandwidth. Think GF2 GTS on a truckload of steroids.

You guys look at tomorrow with the realities of today in mind. Remember, this thing will not be on sale for like another TWO YEARS, that's a long time in this business. 128-bit (256 pins with diff signalling), 400 true MHz bus will most likely not be out of reach then. Remember, Sony will want to stick just one device per memory channel like in PS2 and solder it straight to the mobo instead of have it sitting on a separate piece of board through a connector, this fixes a lot of timing issues that only appears when daisy-chaining devices on a memory stick. Also remember, we know Sony will initially take it on the chin profit-wise when it comes to the hardware and SMILE. So what if each machine costs a small fortune to build, they're out to win the war, not the battle...

You guys lack vision. Heinlein wrote sci-fi fiction where people used slide rules in space because he couldn't envision the advent of a little simple thing called the pocket calculator (or desktop PC for that matter). You're like him, you worry over CURRENT problems and apply them to tech that isn't set to appear until the middle of the bloody decade!

Do I want PS3 with hundreds of gigabytes per second of main memory bandwidth? YES. will that happen? No.
We will get a PS3 with dozens of gigabytes per second of main memory bandwidth. how many dozens is the question. probably 2 or 4 dozen GB
(25-50 GB)

 

[megadrive0088]

so what kind of main memory is expected for XBox2/XBox Next -
something like GDDR-3 or GDDR-4?

 

[nonamer]

so what kind of main memory is expected for XBox2/XBox Next -
something like GDDR-3 or GDDR-4?

I find it hard to believe that the Xbox "2" will use anything less that what's already available, which is the 256-bit 800Mhz GDDR-3. By that I mean in specs, not the same GDDR-3 now since it needs to be cheaper AFAIK.

 

[jvd]

so what kind of main memory is expected for XBox2/XBox Next -
something like GDDR-3 or GDDR-4?

I find it hard to believe that the Xbox "2" will use anything less that what's already available, which is the 256-bit 800Mhz GDDR-3. By that I mean in specs, not the same GDDR-3 now since it needs to be cheaper AFAIK.

mabye for the gpu but the cpu will use whatever ddr ram is top of the line at the time. Mabye ddr 500 or 600.

 

[Vince]

Mabye for the gpu but the cpu will use whatever ddr ram is top of the line at the time. Mabye ddr 500 or 600.

No UMA? That was one of the coolest parts of the 'box IMHO.

 

[jvd]

Mabye for the gpu but the cpu will use whatever ddr ram is top of the line at the time. Mabye ddr 500 or 600.

No UMA? That was one of the coolest parts of the 'box IMHO.

vince do you really think they can afford to go that route this time ? Whatever ram the gpu uses will be over kill for a p4 or a64 chip . So it might be cheaper to go with a 128 or 256megs of ddr and use the qddr for the graphics.

 

[Vince]

vince do you really think they can afford to go that route this time ? Whatever ram the gpu uses will be over kill for a p4 or a64 chip . So it might be cheaper to go with a 128 or 256megs of ddr and use the qddr for the graphics.

Yes, I do.

 

[jvd]

vince do you really think they can afford to go that route this time ? Whatever ram the gpu uses will be over kill for a p4 or a64 chip . So it might be cheaper to go with a 128 or 256megs of ddr and use the qddr for the graphics.

Yes, I do.

alright then. Guess we will see haha .

 

[Panajev2001a]

Grall... Cell chips do not only have e-DRAM, they have tons of registers ( 32 registers per APU ) and SRAM ( 128 KB of Local Storage per APU )... the local bandwidth will be huge, rendering will happen there and we might see Vertex data processed by the CPU pass through a Redwood connection to the GPU and not using the main RAM ( this is a similar approach to what PlayStation 2 does with the GIF-to-GS bus ).

All rendering happens on chip, the frame-buffers, Z-buffers, stencil buffers, all of them are stored inside the e-DRAM of the GPU and on both CPU and GPU we should have enough total storage to keep quite a bit of data inside...

We have BIG local buffers on CPU and GPU, it is not like we are rendering directly from main RAM...

PlayStation 2 uses 3.2 GB/s main RAM and the Xbox has a UMA approach with frame buffers stored in the shared memory pool and the total bandwidth is only 6.4 GB/s...

Here we are talking about 8x the bandwidth you had on PlayStation 2 and with probable LOWER latency... also now the CPU ( unlike the EE ) has a more than decent amount of local memory as well as the GPU...

I do not see why they should push for 50 GB/s considering the costs...

I do not think this would kill the performance and I believe that the money saved can be invested in things like Blu-Ray who deserve the push too...

At 25.6 GB/s we can transfer the whole 256 MB of main RAM in ~9.75 ms which is less than 59% of the total frame time ( 1/60th of a second would be total frame time ).