[function]

Originally Posted by itsmydamnation

i didn't know thats all the PS3 has to offer??? oh wait.........
So maybe thats the developers fault for not considering the systems they where developing for.

Well when you put it like that, I guess there's no need at all for Cell to be able to access half of the platform's memory.

Memory is clearly overrated. Only lazydevs and hacks benefit from being able to access it all at will, especially on the (usually) worse performing "port target" platform that has both less available and less total memory.

[onQ]

Originally Posted by itsmydamnation

first remember the context, the issue is getting 4gig of GDDR5 and then also the cost. so now people are talking 2+2 or 4+2 etc

Memory throughput hasn't been a big bottleneck for low core count CPU's for ages now (latency is).
why would the GPU have to drop down to CPU memory speed (what does that even mean)?

CPU workloads care about latency what has lower latency DDR3 or GDDR5? I cant find a really good answer, it looks like GDDR5 read/write at 256bits and DDR3 at 128bits so non linear access to memory might be better with DDR3 but its running at higher base frequencies then DDR3.

seeing a comparison of random read / random write and sequential read/write at 32/64/128/256 bit word lengths would be very interesting to see.

but even if GDDR5 has better latency and throughput then DDR3 it doesn't matter for what i was talking about because its still just a form of memory QOS. you put data in the location that best matches its usages requirements. Even if you put some of your GPU data on the DDR3 it doesn't mean your throughput drops, infact it likely increases.


im not saying this is a good idea, because the reality is your now at a 256bit bus and assuming cost isn't the issue you just go 4gig GDDR5 ( again assuming its all round better memory).

my point was just because its two different memory types doesn't mean it needs to be two different "pools"



i didn't know thats all the PS3 has to offer??? oh wait.........
So maybe thats the developers fault for not considering the systems they where developing for.

I think if they are running code in parallel on the CPU & GPU they will have to be using the same bandwidth so I'm pretty sure they wouldn't want the GPU to have to use slower bandwidth just to work with the CPU so why not have fast Ram for both the CPU & GPU?

PS3 used XDR for it's CPU memory so I think it would be a step back to use DDR3 for the PS4 CPU.



Speaking of XDR I remember seeing something about newer AMD high end GPUs using XDR2 could that be what Sony is planing to use in the PS4 & the reason they are looking at 2GB of Ram for the PS4?




XDR™2 Memory Architecture

The XDR™2 memory architecture is the world's fastest memory system solution capable of providing more than twice the peak bandwidth per device when compared to a GDDR5-based system. Further, the XDR 2 memory architecture delivers this performance at 30% lower power than GDDR5 at equivalent bandwidth.

Designed for scalability, power efficiency and manufacturability, the XDR 2 architecture is a complete memory solution ideally suited for high-performance gaming, graphics and multi-core compute applications. Each XDR 2 DRAM can deliver up to 80GB/s of peak bandwidth from a single, 4-byte-wide, 20Gbps XDR 2 DRAM device. With this capability, systems can achieve memory bandwidth of over 500GB/s on a single SoC.

Capable of data rates up to 20Gbps, the XDR 2 architecture is part of the award-winning family of XDR products. With backwards compatibility to XDR DRAM and single-ended industry-standard memories, the XDR 2 architecture is part of a continuously compatible roadmap, offering a path for both performance upgrades and system cost reductions.



The XDR 2 memory architecture is the first to incorporate innovations from Rambus' Terabyte Bandwidth Initiative along with other key Rambus innovations including:

32X Data Rate enables high data rates (up to 20Gbps) at lower system clock and on-chip bus interface speeds.

Fully Differential Memory Architecture (FDMA) improves signal integrity, reduces power and enables the highest memory performance available.

Enhanced FlexPhase™ enables high data rates, simplifies layout and eliminates trace length matching.

FlexLink™ C/A reduces system costs and controller pin-count while providing scalable capacity and flexible access granularity.

FlexMode™ interface technology enables support of both differential and single-ended memories in a single SoC package design with no extra pins.

Micro-threading increases transfer efficiency on micro-threaded workloads while reducing power consumption.

[Grall]

Originally Posted by onQ

PS3 used XDR for it's CPU memory so I think it would be a step back to use DDR3 for the PS4 CPU.

DDR3 is what CPUs use these days, so that's what it'll be. It's not a "step back". DDR3 can easily match or exceed the XDR memory bus of the PS3 today, and DDR3 chips are cheap, mass-produced commodity products while XDR remains extremely fringe (nevermind XDR2 which doesn't even exist except on paper, and maybe prototype form from what I understand.)

[novcze]

Originally Posted by Grall

DDR3 is what CPUs use these days, so that's what it'll be. It's not a "step back". DDR3 can easily match or exceed the XDR memory bus of the PS3 today, and DDR3 chips are cheap, mass-produced commodity products while XDR remains extremely fringe (nevermind XDR2 which doesn't even exist except on paper, and maybe prototype form from what I understand.)

If they are going with stacked memory, isn't completely irrelevant what is mass-produced and what not?

[Shifty Geezer]

Is there any benefit to XDR in stacked form? I don't know how the bus format affects stacked access.

[SKYSONY]

bgassassin, whose post are always interesting to read, keeps saying the Durango´s GPU s will be less powerful than PS4 one. I thought he has mostly the same sources than lherre, but, apparently his info comes from a difference person.

It appears to me that the 720 dev kits (probably where all indiser info comes from) are constantly evolving, since back in November IGN said the GPU was a 6670, that is only 0.7 TFLOPS. If when bg got the > 1 TF info the dev kits were not the final ones, we might see a better number with the next leak.

[upnorthsox]

Originally Posted by Grall

DDR3 is what CPUs use these days, so that's what it'll be. It's not a "step back". DDR3 can easily match or exceed the XDR memory bus of the PS3 today, and DDR3 chips are cheap, mass-produced commodity products while XDR remains extremely fringe (nevermind XDR2 which doesn't even exist except on paper, and maybe prototype form from what I understand.)

Actually DDR3 can't, and it only comes close with highly cherry-picked, extreme overclocked dimms with a pricetag that makes xdr seem like a bulk commodity item. And PS3 is only running it at half clock so the comp is even more one sided.

XDR2 should have been a stacked solution from the get go, especially in an LP variant. That was Rambus's big mistake, they misjudged where the market is going. They could've had Apple.

[Kb-Smoker]

Lherre saying leak ps4 specs were from last year. Amd just made some major improvements with rumor gpu so we could see some boost in performance just from this.

To begin with, AMD has worked with TSMC to refine the chip design. The Tahiti XT2 will be able to facilitate significantly higher clock speeds, at significantly lower voltages, than the current breed of Tahiti XT chips.

Tahiti XT2, or Radeon HD 7970 GHz Edition, will ship with a core clock speed of 1100 MHz, 175 MHz faster than the HD 7970. The GPU core voltage of Tahiti XT2 will be lower, at 1.020V, compared to 1.175V of the Tahiti XT.

big drop in voltage and raised clock speed.


http://www.techpowerup.com/167711/AM...-Detailed.html

Originally Posted by SKYSONY

bgassassin, whose post are always interesting to read, keeps saying the Durango´s GPU s will be less powerful than PS4 one. I thought he has mostly the same sources than lherre, but, apparently his info comes from a difference person.

It appears to me that the 720 dev kits (probably where all indiser info comes from) are constantly evolving, since back in November IGN said the GPU was a 6670, that is only 0.7 TFLOPS. If when bg got the > 1 TF info the dev kits were not the final ones, we might see a better number with the next leak.

Well bg info is all second hand. Iherre is a proven game developing and info is first hand.

[tunafish]

Originally Posted by Shifty Geezer

Is there any benefit to XDR in stacked form? I don't know how the bus format affects stacked access.

There's a considerable downside -- DE buses are comparatively better the longer the traces need to be. In a stacked system, DE signaling is just a complete waste of silicon.

XDR2 should have been a stacked solution from the get go, especially in an LP variant. That was Rambus's big mistake, they misjudged where the market is going. They could've had Apple.

Rambus simply has no capability to design good stacked systems. Their strengths, in patents and experience, are in DE signaling and compensating for bad signal paths. None of that is useful for designing stacked memory systems.

[upnorthsox]

Originally Posted by tunafish

There's a considerable downside -- DE buses are comparatively better the longer the traces need to be. In a stacked system, DE signaling is just a complete waste of silicon.



Rambus simply has no capability to design good stacked systems. Their strengths, in patents and experience, are in DE signaling and compensating for bad signal paths. None of that is useful for designing stacked memory systems.

True, it would've been out of their comfort/expertise zone but better than being shut out completely.

[onQ]

Originally Posted by Grall

DDR3 is what CPUs use these days, so that's what it'll be. It's not a "step back". DDR3 can easily match or exceed the XDR memory bus of the PS3 today, and DDR3 chips are cheap, mass-produced commodity products while XDR remains extremely fringe (nevermind XDR2 which doesn't even exist except on paper, and maybe prototype form from what I understand.)

& DDR2 is what CPUs used back when the PS3 was being designed & XDR didn't exist except on paper, and maybe prototype form.

Originally Posted by Shifty Geezer

Is there any benefit to XDR in stacked form? I don't know how the bus format affects stacked access.

Originally Posted by tunafish

There's a considerable downside -- DE buses are comparatively better the longer the traces need to be. In a stacked system, DE signaling is just a complete waste of silicon.



Rambus simply has no capability to design good stacked systems. Their strengths, in patents and experience, are in DE signaling and compensating for bad signal paths. None of that is useful for designing stacked memory systems.

Maybe Sony will stack the memory like they stacked it on the Vita SOC, where it's stacked on the chip but it's not TSV, & if XDR2 can achieve 32X Data Rate does it really need to be stacked using TSV?

wouldn't XDR2 be the perfect stop gap right now to achieve the bandwidth that they are going for with stacked ram?

or am I missing something?

[antwan]

Originally Posted by onQ

& DDR2 is what CPUs used back when the PS3 was being designed & XDR didn't exist except on paper, and maybe prototype form.






Maybe Sony will stack the memory like they stacked it on the Vita SOC, where it's stacked on the chip but it's not TSV, & if XDR2 can achieve 32X Data Rate does it really need to be stacked using TSV?

wouldn't XDR2 be the perfect stop gap right now to achieve the bandwidth that they are going for with stacked ram?

or am I missing something?

XDR2 would be perfect, it will deliver a lot of bandwidth, even without stacking, that is correct.
It is expensive though, and like XDR before it, it has not yet been used so I don't know if it's certain to work like it's advertised..

[onQ]

Originally Posted by antwan

XDR2 would be perfect, it will deliver a lot of bandwidth, even without stacking, that is correct.
It is expensive though, and like XDR before it, it has not yet been used so I don't know if it's certain to work like it's advertised..

Wouldn't that be the same case with Stacked Ram?


& also I see that XDR2 can go up to 4Gbit chips which is 512MB so they can fit 8 memory chips on a 256bit bus & have 4GB of Ram & achieve 409.6GB/s bandwidth.

but like you said price would be expensive.


PS: I really don't know much about this stuff but I'm a quick learner & this is what I got from reading about it so I could be way off with what I'm saying.

[Grall]

Originally Posted by upnorthsox

Actually DDR3 can't, and it only comes close with highly cherry-picked, extreme overclocked dimms with a pricetag that makes xdr seem like a bulk commodity item. And PS3 is only running it at half clock so the comp is even more one sided.

What on earth are you talking about? The 21ish GB/s that the PS3 XDR bus manages is extremely attainable with DDR3, without resorting to esoteric clock speeds.

[liolio]

My memory is telling me that latencies were far from great with xdram.
Anyway, this memory thing has been widely discussed in the proper thread I see no point going back there.

[antwan]

I imagine Kaz Hirai going to the Rambus' CEO, who is in the hospital and the CEO is saying something like:

We were in this together.. the state of the art PlayStation must return

Kaz:

what if he doesn't exist anymore?

CEO:

He must... he must

To me Rambus memory is what PlayStation has always been about. High-end. It would be a shame if they went with DDR3 or something like that, it will bite them in the long run, when they want to have the platform for +3 years..

[Grall]

Never heard anything bad about XDR's latencies. It's used in high-end routers and such which ought to be very latency-sensitive methinks. Old DRDRAM could have bad latency if many devices resided on the same memory channel, but in PS2 only had one device per channel, so latency was apparantly roughly comparable to regular SDRAM in that case.

[onQ]

Originally Posted by Grall

What on earth are you talking about? The 21ish GB/s that the PS3 XDR bus manages is extremely attainable with DDR3, without resorting to esoteric clock speeds.

PS3 had 128bit main memory bus, DDR3 would have only been able to manage about 12GB/s in the PS3 & if the PS4 is 256bit DDR3 would only get about the same main memory bandwidth as the PS3 using 4 64bit 1GB DDR3 chips.


So it would be 4GB of memory in the PS4 but only about the same bandwidth as the PS3.


(That's if I'm doing this right.)

& with that same 256bit bus the PS4 could have 224GB/s (about 10 X the bandwidth of the PS3 ram) using 8 32bit 256MB GDDR5 chips for 2GB of ram.

or 409.6 GB/s (about 20 X the bandwidth of the PS3 ram) using 8 32bit 512MB XDR2 chips for 4GB of ram.

[Grall]

Originally Posted by onQ

PS3 had 128bit main memory bus, DDR3 would have only been able to manage about 12GB/s in the PS3 & if the PS4 is 256bit DDR3 would only get about the same main memory bandwidth as the PS3 using 4 64bit 1GB DDR3 chips.

RSX in PS3 also has a 128-bit DDR3 memory bus, as do Xbox 360 btw and still reaches the same bandwidth.

So no, there's nothing magic about XDR in PS3... Even though it's only 64-bit in width it uses differential signaling, thus needing two pins per bit = 128 pins total for the full databus.

[onQ]

Originally Posted by Grall

RSX in PS3 also has a 128-bit DDR3 memory bus, as do Xbox 360 btw and still reaches the same bandwidth.

So no, there's nothing magic about XDR in PS3... Even though it's only 64-bit in width it uses differential signaling, thus needing two pins per bit = 128 pins total for the full databus.

The RSX & Xbox 360 use GDDR3 not DDR3 unless I missed something.

[bkilian]

Originally Posted by Grall

What on earth are you talking about? The 21ish GB/s that the PS3 XDR bus manages is extremely attainable with DDR3, without resorting to esoteric clock speeds.

in fact, the cheaper gddr3 on the 360 is 25.6GB/s.

[pjbliverpool]

Originally Posted by onQ

PS3 had 128bit main memory bus, DDR3 would have only been able to manage about 12GB/s in the PS3 & if the PS4 is 256bit DDR3 would only get about the same main memory bandwidth as the PS3 using 4 64bit 1GB DDR3 chips.


So it would be 4GB of memory in the PS4 but only about the same bandwidth as the PS3.


(That's if I'm doing this right.)

& with that same 256bit bus the PS4 could have 224GB/s (about 10 X the bandwidth of the PS3 ram) using 8 32bit 256MB GDDR5 chips for 2GB of ram.

or 409.6 GB/s (about 20 X the bandwidth of the PS3 ram) using 8 32bit 512MB XDR2 chips for 4GB of ram.

You'll get 25.6 GB/s with 1600Mhz DDR3 on a 128bit bus. But you can get higher speed DDR3 than that.

[Grall]

Originally Posted by onQ

The RSX & Xbox 360 use GDDR3 not DDR3 unless I missed something.

Whatever. It's not a difference that changes anything on a fundamental level.

[Kaotik]

Originally Posted by Grall

Whatever. It's not a difference that changes anything on a fundamental level.

It changes quite a lot, GDDR3 is based on DDR2, and DDR3 is quite a bit different standard.

[onQ]

Originally Posted by Grall

Whatever. It's not a difference that changes anything on a fundamental level.

Yes it does.