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Potentially bad news for PS3 memory, thus PS3 games. Possibly only 128 MB XDR RAM

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GigaDrive

Banned
http://www.beyond3d.com/forum/viewtopic.php?p=322279#322279

Passerby wrote:
http://pc.watch.impress.co.jp/docs/2004/0709/kaigai101.htm

Summary:

1) The schedule of Toshiba, Samsung and Elpidia for production of XDR DRAM has been adjusted to be later, as the main customer - Sony's PS3 is scheduled for a 2006 release instead of 2005, as was projected last year.

2) All 3 manufacturers are no longer aiming for 512Mbit chips, but 256Mbit instead. PS3 memory will be composed of 256Mbit techology. Reason quoted "to reduce cost and requested by customers".

3) The article discusses that last year, when PS3 memory was thought to be made of 512Mbit chips, estimates point to 4 mem chips @ 256MB @ 25GB/s. However, the new announcement of moving to 256Mbit may result in some possibilities - 8 mem chips @ 512MB @ 51GB/s.

4) Even a talk about PS3 - the biggest customer. Talk of how fast memory is vital for next-generation console, how a multi-core architecture can be easily bottlenecked by inefficient memory design.

nAo wrote:

Umh..8 chips?? My bets are on 4 256 Mbit/s modules, 25.6 GigaBytes/s.
As a developer I can live with a 128 megabytes external memory console..


basicly it boils down to this: IF PS3 uses the 256 Mbit (megabit not megabyte) XDR chips (these are 32 MB) and the best guess is, PS3 will use 4 of these memory chips due to cost, the PS3 will be left with just 128 MB of external memory. it would need 8 of these 256 Mbit chips to have 256 MB external memory. or 16 chips to reach a respectible 512 MB.

it was assumed that PS3 would use the 512 Mbit (64 MB) XDR chips. therefore 4 such chips would give it 256 MB, or 8 chips for 512 MB. with the 256 Mbit memory chips, it makes more difficult to reach 256 MB or 512 MB because obviously you need more chip modules.

Panajev, what say you?
 
Well I guess the cost cutting measures are going to have to come in at some point. Seems like the road to profitability might even affect the PS3 (omg!) ;).
 

HyperionX

Member
GDDR-3 is exactly where XDR will be according to this article, 256Mb at 25.6GB/s for a 4 chip solution. Thing is, GDDR-3 is available now whereas XDR won't be for some time.
 

Lord Error

Insane For Sony
GDDR-3 is exactly where XDR will be according to this article, 256Mb at 25.6GB/s for a 4 chip solution. Thing is, GDDR-3 is available now whereas XDR won't be for some time.
Actually, in 2006 (or sooner), XDR will be at least 51GB/s.
 

GigaDrive

Banned
Xbox 2's memory according to both the supposed block diagram and the supposed text document said 256+ MB memory @ ~22 GB/sec

so yeah, probably the same type of complaints about Xbox 2 specs
 

BeOnEdge

Banned
i dont understand why people would complain either way. X and ps2 have 64, and you are bumping it to 4x that without needing an OS and crap running in the background to bog down ram, WHATS THE PROBLEM.
 

Buggy Loop

Member
BeOnEdge said:
i dont understand why people would complain either way. X and ps2 have 64, and you are bumping it to 4x that without needing an OS and crap running in the background to bog down ram, WHATS THE PROBLEM.

Ps2 doesnt have 64MB..
 

Insertia

Member
i'll believe this when Sony releases the tech sheet. No way in hell will PS3 have less RAM then Xbox2 (256MB, correct?); not if X2 launches in 05 and PS3 06.
 

GigaDrive

Banned
in english (or rather engrish!)

- Directing to the board during 2005, the DRAM vendor runs

The next generation PlayStation (PlayStation 3? ) The memory XDR DRAM which is adopted (Yellowstone: イエロストー&#12531 the road map, this week is held in Tokyo, with "Rambus Developer Forum (RDF) Japan 2004" it became clear.


The engineering sample of XDR DRAM of Samsung
As for the latest important update 2 points below. (1) there is no big modification in the schedule of XDR DRAM which is required on DRAM vendor side, there is no big modification in the schedule = PlayStation 3. (2) specification of memory which is loaded onto PlayStation 3 was modified, was not the 512Mbit tip/chip and it became the 256Mbit tip/chip.

The largest customer of XDR DRAM, the SONY computer entertainment (SCEI) PlayStation 3 as for being is open secret. Powerful application for the time being sees in other things and from the fact that it does not hit, the start-up of XDR DRAM is presumed that PlayStation 3 bears. In other words, it links the schedule and specification of XDR DRAM, closely with the schedule and specification of PlayStation 3.

(1) XDR DRAM schedule is almost the sort of RDF of last year. Toshiba which takes charge of the development/the production of XDR DRAM, 3 corporations of エルピーダメモリ and Samsung Electronics being even, start the production of XDR DRAM in the board during 2005. This has meant the fact that start of the production of PlayStation 3 is set to the board during 2005. In other words, PlayStation 3 during 2005, how being slow, is that the possibility of appearing to 2006 first half is high. Schedule of DRAM side from the almost same thing, as for the schedule of PlayStation 3, from last year largely it is presumed that it is not modified.

Actually, as for a certain industry authorized personnel "as for the schedule of present XDR DRAM, you say that the timing which very limit is in time in schedule of the largest customer" is. In addition, another industry authorized personnel "is not the case that 3 corporations have kept pace separately. It does not become the same timing you do not obtain as a result ", whether or not" it is in time to the schedule which destination requires, you think that with, use ratio of the XDR DRAM memory 3 is decided. Because of that, you must defend desperately schedule, ", you said.

By the way, presently, as for the Cell processor which is the heart of PlayStation 3, already completing the design, it has become clear for the sample to have come out. In the Cell processor itself, interface of XDR DRAM memory is seen that it is built in. Toshiba and Samsung have already produced the first silicon which has been designed with 512Mbit, using that, it is presumed that the operation verification of Cell is done. With this, it is the case that the trend of the inside two of the principal components of PlayStation 3 has become clear.


The latent market of XDR DRAM due to Toshiba The Toshiba with RDF of last year latency market estimate


- Is loaded onto PlayStation 3 the memory chip which in modification

With schedule it is XDR DRAM which is not modification, but in product plan there was big modification. That is capacity of memory chip.

At stage of last year, as for XDR DRAM it was the schedule which it mass-produces starts from the 512Mbit tip/chip. You started also 3 corporations, first with 512Mbit, as for the 256Mbit tip/chip the cutdown edition from 512Mbit (as for the design of the basis it is same) you had come to the point of throwing with following. However, presently, also 3 corporations it has changed to the policy of starting production from the 256Mbit tip/chip. For example, a certain vendor cancels the design of the 512Mbit tip/chip which was developed, has done again to design 256Mbit to main.


Samsung XDR DRAM road map The Toshiba XDR DRAM road map The Toshiba with RDF of last year road map


This meaning simply one. The memory chip which is adopted for PlayStation 3, from 512Mbit is dense to 256Mbit Toda who becomes modification. Actually, a certain industry authorized personnel "has heard that for cost reduction, request of the customer in 256Mbit became modification," that you say.

From 512Mbit the modification to 256Mbit not being limited to a simple story that the memory chip which is loaded onto PlayStation 3 changed. It suggests that it is important modification in the specification itself of PlayStation 3. As for the possibility of being thought two. (1) the memory quantity which is loaded onto PlayStation 3, from 256MB of expectation of beginning was reduced by half to 128MB. (2) the memory zone of PlayStation 3, was redoubled to approximately 51.2GB/sec from approximately 25.6GB/sec of expectation of beginning. The possibility of having this either modification is high.

In case of former it means to decrease the memory quantity for cost reduction and, in case latter it means to increase memory zone for efficiency request. In case latter, there is a possibility of having modification even on memory interface side of the Cell processor and the media engine of PlayStation 3.




- PlayStation 3 where the around of memory is strengthened

As for PlayStation 3, when you compare with PlayStation 2, around the memory it is strengthened relatively. Concretely, it reaches the point where many DRAM tips/chips are loaded. With latest XDR DRAM, as for the largest reason where 3 DRAM vendors enter there is there. Last year, as for a certain DRAM industry authorized personnel the number of DRAM tips/chips which PlayStation 3 loads is many "PlayStation 2 compared to. Therefore, there is an entry chance for the DRAM vendor ", you said.

Applying development cost, the die/di (the semiconductor itself) you design, cut the production line, with just PlayStation 3 you can expect the quantity which it pays sufficiently. That, it is the basis which enters into XDR DRAM. If "the equipment which loads several XDR DRAM comes out, annual several 10000000 units, per month the demand for 1,000 ten thousand XDR DRAM is born with just that. Dividing at 3 corporations, at a time 300 ten thousand. Then, it can keep doing sufficiently, "that a certain industry authorized personnel says.

And, at stage of the summer of last year, as for the number of XDR DRAM tips/chips which are loaded onto PlayStation 3 it was presumed that 4 is. 4 calls number, because the plural sources have suggested, is thought that it was secure.

As explained already, last year as for XDR DRAM 512Mbit (32Mx16) with, because it was the schedule which is started, the memory capacity of PlayStation 3 was the possibility that it becomes 256MB. In addition, as for XDR DRAM for the time being because x16 (configuration modification it is possible) is even to x4/x8, as for memory interface width it was seen that it becomes 16bit×4 = 64bit.

By the way, as for XDR DRAM for the time being the product where the plural speeds of 2.4Gtps - 4Gtps differ (derivation) is planned, but as for aiming for the high yield at stage 2005 3.2Gtps (as for tRAC 60ns) the product. Because of that, it is seen that this specification is adopted for also PlayStation 3. So when it does, the memory zone of PlayStation 3 was supposed that it becomes the memory zone of 3.2Gtps×64bit = approximately 25.6GB/sec.

- As for the memory zone of PlayStation 3 50GB/sec?

However, because the loading DRAM PlayStation 3 from 512Mbit to 256Mbit it becomes modification, as for this presumption it changed.

First, when we assume that SCEI for cost reduction modified to 256Mbit, it means that in order 4 with while is to designate the capacity of the tip/chip as half, the on-board memory quantity reduces by half the memory quantity to 128MB. 128MB when you thought, as the computing device of 2005 - 10 years is the rather harsh number, but as for SCEI originally as for the footprint of memory because there is a tendency which is reduced to very limit, it is not the story where this is not possible.

But while SCEI holding down the memory quantity, when we assume that it tried to expand memory zone story is different. In other words, while it is 256MB, the number of tips/chips increasing the memory quantity of PlayStation 3 to 8 from 4, there is also a possibility that much of designating memory zone as 2 times.

In that case, the memory interface of PlayStation 3 becomes 128bit width at total, to 3.2Gtps×128bit = approximately 51.2GB/sec redoubles memory zone. RADEON X800 of ATI Technologies XT Platinum Edition (R423/R420) memory with GDDR3 1,120Mtps zone 35.8GB/sec. When we assume, that PlayStation 3 is 51.2GB/sec, it means the memory zone which exceeds that much.

There are several bases in the possibility the number of latter memory chips increasing. First, DRAM itself from the 512Mbit center to the 256Mbit center became modification the point where the estimate quantity of the latent market which Toshiba shows with RDF in spite, has not been different from RDF of last year.


Estimate of the memory zone needs with Rambus
Toshiba with 512Mbit tip/chip conversion, showed the completely same figure. In other words, as for the tip/chip, as for the bit quantity itself of the latent market it does not change even with 256Mbit, (the memory quantity which is loaded onto the equipment does not change) with is the viewpoint which is said. In addition, with RDF Rich Warmke of Rambus (Marketing Director and Memory Interface Division), as for demand for memory zone when it is getting near to 50GB/sec, it was shown even in the presentation as a trend.

Like this, when it tries doing, the characterization of PlayStation 3 changes rather, according to the specification of PlayStation 3 changed to either one, but verification does not do yet. With says, XDR DRAM which is loaded onto PlayStation 3, from 512Mbit as for just having become modification is secure to 256Mbit.

In 2005 either capacity of 256Mbit or 512Mbit the appropriateness?, it is rather difficult problem. In other words if you say concerning main stream DRAM, because 2005 is the time when exactly it approaches to shift. Whether or not during 2005 from 256Mbit the bit cross to 512Mbit (the unit cost per bit crosses) comes in two capacity generations, doubt apparent it is done, but when you think of that also after 2006 sells, we would like to begin new memory from 512Mbit as a DRAM vendor. When it becomes from 2007 first, because because relatively bit unit cost becomes expensive, it becomes difficult to sell the 256Mbit item, to other than PlayStation 3.


- SCEI explaining the technical trend of the PlayStation 3 generation

In addition, with RDF Yutaka of the SONY computer entertainment 禎 Osamu (software platform development department department manager), did keynote speech concerning the vision of PlayStation.


Trend of evolution of game console
First, completeness and multiple core conversion of operational unit of SIMD/ vectoring type were listed as the technical trend of CPU concerning the game console itself. As known already, the Cell processor which PlayStation 3 loads, is seen that vectoring unit central multiple core architecture is taken. Is not new news, but as for Yutaka it is the appearance which confirms that.

In addition, the to high clock memory did not overtake CPU which is converted vis-a-vis CPU- memory, when the fact that メモリレイテンシ increases is problem explained. The same person only large increasing capacity of cash showed as a concrete レイテンシ measure, but multiple core architecture itself is an effect even in concealment in regard to the appearance of メモリレイテンシ. Because one core the stall while having done, can operate another core with the data waiting from memory.

Yutaka, with memory trend, said that large increasing capacity and band widening become important. The memory capacity of PlayStation 3 decreased even from this context with is difficult to think. By the way, also a certain Cell authorized personnel, said that zone of the bus/memory has become the bottleneck of the most importance, as the technical trend of CPU.

In addition, as for Yutaka concerning the trend of the future digital contents it explained. First as computing power of the game machine increases as a trend, when it expands also the zone of communication below, furthermore also the contents change by the fact that it reaches the point where both tropism is loaded usually in the game machine, the viewpoint was expressed. The fact that you list as example is multifarious utilization of the contents material then.

For example, with the contents like the movie, image itself being formed with computer, so far as for interactive characteristic it was not. As for being able to enjoy the user, finally rendering just the CG movie which is done. In other words, complying with the time base only degree of freedom it was it advances the movie and it rewinds.

But if with environment of user side, it reaches the point where formation environment of the material such as that can be kept every roundly, story changes. With reuse of the same material, the question っ callous which the user operates to interactive becomes possible. With the quality of CG of the movie, it is the case that also the game becomes possible.

Also this story, as the Hisashi of SONY /SCEI 夛 the wooden health person (SONY vice president/SONY computer entertainment president and CEO) talks so far well. It means that the vision is getting near to actuality finally.
 

GigaDrive

Banned
PS2 has 32 MB main memory, but 40 MB in total.

32 MB main
4 MB eDRAM on GS
2 MB audio memory
2 MB for I/O processor (PS1 CPU)






so it seems, if the watch impress article can be believed, PS3's main external memory will be high-bandwidth (50~51 GB/sec) but low quantity (128 MB)


damnit, I want 102 GB/sec bandwidth and 512 MB!

I hope developers bitch like crazy to SCEI, like they must have done over PSP. Sony basicly tripled the memory in PSP, from 12 MB to 36 MB, although the amount of eDRAM was cut to 1/3 from 12 MB to 4 MB. (PSP has 32 MB plus 4 MB eDRAM).

come on developers, let your voices be HEARD!
 

P90

Member
GigaDrive said:
I hope developers bitch like crazy to SCEI, like they must have done over PSP. Sony basicly tripled the memory in PSP, from 12 MB to 36 MB, although the amount of eDRAM was cut to 1/3 from 12 MB to 4 MB. (PSP has 32 MB plus 4 MB eDRAM).

come on developers, let your voices be HEARD!

The contrasting issue is that the PS3 will reign, while the PSP will be a speck in the GBA's rearview mirror. The PSP, from what is out so far about it, sounds ill-conceived, to put it politically correct.
 

Arcticfox

Member
For the Cell architecture bandwidth is much more important than quantity. If they have to make a compromise I am happy that they seem to be concentrating on the speed of the memory.
 

GigaDrive

Banned
yeah, developers could live with 256 MB of 50+ GB/sec memory, but just 128 MB? cripes that's awful.

hell, early in this generation, top developers commented that PS2 should have been give 128 MB main memory to take advantage of the power of its processors.
 

Panajev2001a

GAF's Pleasant Genius
128 MB at 51.2 GB/s, it might seem crazy, but it would make sure the CELL chips are running at peak efficiency and if developers go crazy with very funky geometry and texture compression algorithms which are computationally heavvy, it might all work out.

That is about more than 2x the bandwidth Xbox 2 will have for its main RAM and we have not taken count of any e-DRAM on the GPU and possibly on the CPU of PlayStation 3.
 

teh_pwn

"Saturated fat causes heart disease as much as Brawndo is what plants crave."
128 MB just isn't enough. Unless all games are going to run at 640X480i again....ugh.
 

GigaDrive

Banned
well Panajev, the 22.4 GB/sec main memory bandwidth for Xbox 2, from that block diagram and from that text document, could be very very old or bogus. an older article on Xbox 2 said the mem bandwidth would be ~51 GB/sec which is more believable. So Xbox 2 and PS3 main memory bandwidth could end up being similar. but Xbox 2 will have at least 256 MB memory, though probably not as much eDRAM as PS3.
 

Panajev2001a

GAF's Pleasant Genius
GigaDrive said:
well Panajev, the 22.4 GB/sec main memory bandwidth for Xbox 2, from that block diagram and from that text document, could be very very old or bogus. an older article on Xbox 2 said the mem bandwidth would be ~51 GB/sec which is more believable. So Xbox 2 and PS3 main memory bandwidth could end up being similar. but Xbox 2 will have at least 256 MB memory, though probably not as much eDRAM as PS3.

We will see what Sony is cooking: I doubt that Xbox 2 will have a year earlier lamost than PlayStation 3 twice the RAM and at he same speed.

We will see when GDDR3 will hit 51.2 GB/s and at what cost for 256 MB of it.

The Xbox 2 document specified at least 10 MB of e-DRAM on the GPU and the ability of the GPU to read data directly from the CPUs' shared L2 cache.

Xenon's CPU system ( the tree cores ) also "only" packs the equivalent of three Altivec units ( one per core ) and aims for less FP power than what the Broadband Egnie in the PlayStation 3 will be probably targeted for.

If ATI's GPU had no e-DRAM I would understand MS's decision for 51.2 GB/s of RAM, but still I think they will pack some e-DRAM in their GPU to keep the efficiency of that chip as high as they can.
 

teh_pwn

"Saturated fat causes heart disease as much as Brawndo is what plants crave."
If games are going to run at 720p, and there's a lot more needed for textures and general rendering, then there's got to be more than 128 MB, unless this system has an optical drive that's faster that jesus and can cache and stream things instantly.

640x480i is probably doable, but it'll be rough with developers.

And comparing generations, we've got 3 MB with PSone --> 32 MB (?) with PS2, that's a factor of 10. PS3 needs 256. Especially if it's going to be in 2006-7.
 

Panajev2001a

GAF's Pleasant Genius
teh_pwn said:
If games are going to run at 720p, and there's a lot more needed for textures and general rendering, then there's got to be more than 128 MB, unless this system has an optical drive that's faster that jesus and can cache and stream things instantly.

640x480i is probably doable, but it'll be rough with developers.

And comparing generations, we've got 3 MB with PSone --> 32 MB (?) with PS2, that's a factor of 10. PS3 needs 256. Especially if it's going to be in 2006-7.

We might have a Blu-Ray drive at 72 Mbps ( 2x ) or even 3-4x ( up to 144 Mbps ).

72 Mbps means 9 MB/s and this would mean at 128 MB would be filled in ~14s.

You are also factoring out e-DRAM for the GPU and probably for the CPU too or possible slower RAM attached to the I/O CPU ( probably the EE shrinked and customized ).

Also, thanks to 51.2 GB/s you would be able to sustain a considerably higher INT OPS and FLOPS rate ( especially FLOPS as FP applications tend to be more bandiwdth hungry and less control dependent ) than with 25.6 GB/s available to you.

More complex shaders is not the only thing you will see I think: very advanced geometry and texture compression algorithms will surface, algorithms that were out of reach real-time rendering in the Consumer Electronics arena due to high performance requirements.
 

GigaDrive

Banned
And comparing generations, we've got 3 MB with PSone --> 32 MB (?) with PS2, that's a factor of 10. PS3 needs 256. Especially if it's going to be in 2006-7.

PS1 main memory 2 MB ====> PS2 main memory 32 MB - thats a 16x leap in main memory

PS1 total memory 3.5 MB ====> PS2 total memory 40 MB - thats slightly over 11x leap in total memory.



but i agree with you, PS3 needs at least 256 MB. that's the bare minimum though, and even that isnt too wonderful.
 

HyperionX

Member
Panajev2001a said:
128 MB at 51.2 GB/s, it might seem crazy, but it would make sure the CELL chips are running at peak efficiency and if developers go crazy with very funky geometry and texture compression algorithms which are computationally heavvy, it might all work out.

128MB seems crazy because it is. With next-gen engines like Unreal 3.0 requiring up to 1GB of RAM 128 will just mean highly compressed textures and the washed out look again. Even if it doesn't, it could still be bad because even if the PS3 has way more power than anything else on the market, it could still potentially look worse by being more difficult to work with.
 

GigaDrive

Banned
the way I see it is (and admittedly my view could be flawed) ...PS3 with 128 MB XDR main memory is like if PS2 had 8 MB RDRAM main memory instead of 32 MB. the PS3 would need 512 MB of XDR memory just to be on par with where PS2 was in 2000 with 32 MB, which itself was concidered skimping. 128 MB for PS3 in 2006....it's beyond pathetic. so pathetic, it just might not be true. but unfortunately it might in fact *be* true, because the info apparently comes from some Rambus developer forum.
 

kaching

"GAF's biggest wanker"
Just to throw a wildcard idea into the mix, the leaked Xenon specs diagram included a video scaler. Wouldn't it make sense that the primary reason to include this would be so that you could render a scene internally at a lower resolution (say 16:9 480p - 720x480) and let the video scaler handle the final rendering to screen at 720p or 1080i (or maybe, just maybe 1080p...)? Since you'd only be rendering at 720x480 internally, you'd have more CPU/GPU resources to create more photorealistic effects and provide better FSAA, for example, and you wouldn't need as much memory.
 

element

Member
With next-gen engines like Unreal 3.0 requiring up to 1GB of RAM 128 will just mean highly compressed textures and the washed out look again.
not really. Mostly because the 1 GB mark Epic is talking about is 1 GB of uncompressed textures loaded on the gfx card RAM. I highly doubt they will actually top 256 MB offloaded to the gfx card when working with compression and data streaming.
 

ChryZ

Member
kaching said:
Wouldn't it make sense that the primary reason to include this would be so that you could render a scene internally at a lower resolution (say 16:9 480p - 720x480) and let the video scaler handle the final rendering to screen at 720p or 1080i (or maybe, just maybe 1080p...)?
IMHO that would be a horrible route in terms of details. The only advantage I could imagine for that atm would be, if you got a fixed res display like a LCD or Plasma TV with a low quality scaler. Xenon's filter may would provide a better picture ... of course in the case, that it is doing a better scaling job than the solution of the TV.
 

GigaDrive

Banned
IGN picked up on the RAM changes

http://ps2.ign.com/articles/529/529524p1.html

New PS3 Details
DRAM gets cut in half, but PS3 is on schedule for 2006.


July 09, 2004 - At the recent Rambus Developer Forum 2004 Japan that was held in Tokyo, some new details about the PS3 have come to light. According to PC Watch, the XDR DRAM chip that is being loaded onto the PS3 has been changed from a 512Mbit chip to a 256Mbit chip. One thing that hasn't changed is that production will get underway next summer, making a launch in the first half of 2006 likely.


As to why this has been changed, some industry insiders have been saying that the change has been for cutting costs, but it may not be so cut and dry. The modification can mean one of two things: the total memory has been dropped or memory bandwidth has doubled from 25.6GB/sec to 51.2GB/sec. Both possibilities are likely and the first one would be for cost-cutting. If it's the latter, however, then more work may be done by the Cell chip.

Check back later when we'll have more information about this development.
 

GigaDrive

Banned
interesting post about Rambus memory in PS2 and PS3

http://forum.teamxbox.com/showthread.php?t=276182&page=3

Ok a few points here... I am tired of hearing theoretical numbers, additionally...historically the biggest problem with RAMBUS RDRAM was two fold, price and latency. The PS2 used PC400 RDRAM from RAMBUS and theoretically could achieve 3.2GB/sec bandwidth and the PS3 from this information is rated to achieve a theoretical 51.2GB/sec bandwidth. I would like to point out this is THEORETICAL and based off a mathematical calculation and does not take in account of things such as latency and architectural inefficiencies. The formula that is used here is basically W*C*P*H/8=B where you multiply the bus width times the clock rate times the number of phases per clock multiply again by the number of channels and then you divide that by 8 to get the byte rate instead of bit rate and you have your theoretical memory bandwidth. It is a popular marketing trick that is used very often especially by video card makers.

Here is the Memory Specifications for the Playstation 2...

RAMBUS RDRAM PC400
---------------------
Bus Width: 16bit
Clock Rate: 400mhz
Phases: 2
Channels: 2
Size: 32MByte

Formula: 16*400*2*2/8=3.2GB/sec

The PS2 memory subsystem uses a 16bit wide bus that is clocked very high at 400mhz and can operate on both edges of a clock cycle (this is basically DDR RAM) and uses 2 channels to do this at the same time. Thus this is why the PS2 has a theoretical potential of 3.2GB/sec of memory bandwidth. However the memory has a very high latency, I believe it was around 60ns though I could be wrong, more than that the architecture also incurs an additional latency on accessing so the majority of any potential benefit from having that much more memory bandwidth is more or less wiped out.

Here is the stated memory specifications for the PS3...

RAMBUS XDR-DRAM PC1600
---------------------
Bus Width: 32bit
Clock Rate: 1600mhz
Phases: 4
Channels: 2
Size: 128MByte

Formula: 32*1600mhz*4*2/8=51.2GB/sec

Much like the PS2 the PS3 follows a very similar memory subsystem, only this time they are using full blown RDRAM instead of the cutdown RDRAM that the PS2 used. But unlike the PS2 the RAM the PS3 is going to use will not be widely available for the PC market. At the time of the PS2 RDRAM was a big thing for the Intel platforms as they was marketing a huge difference in memory bandwidth between RDRAM and SDRAM at the time. Because of this I expect the price of the XDR-DRAM will be more expensive than the RDRAM that the PS2 used and this is the reason why Sony is considering with going with as little as 128MB of XDR-DRAM, because 256MB would really balloon the cost of the system, and remember it is already shaping up to be a very expensive system due to so many proprietary components from companies that may or may not be able to sell these parts in the mainstream. Anyway the PS3 is using a memory bus that is a 32bit wide bus that is clocked very high at 1.6Ghz (1600mhz) and can actually transfer 2 bits of information on both edges of the clock cycle (this is basically Quad Data Rate RAM), originally they was quoting a 25.6GB/sec memory bandwidth but they decided they can seperate this into 2 channels much like RDRAM and thus this is where you get the 51.2GB/sec memory bandwidth estimate. However again the memory has a very high latency of around 60ns (this was stated in that document) and because of the very same reasons why the PS2 memory had latency issues that will reoccur in the PS3, and this is also why the majority of the benefits of the extra bandwidth will disappear. I do think if Sony does end up with going with only 128MB of RAM they will be shooting themselves in the foot and a lot of developers are going to cringe when they find out. All this said the Graphics Synthesizer 3 (the PS3 GPU) will also likely have 4 times the memory the PS2 GS has, which was 4MB. So the PS3 will probably have 16MB of embedded DRAM for the GPU, but like the system memory because it is so small a lot of developers may be turned off by this, but developers are going to do what they can.

Long story short though...

Dont believe the numbers they tell you, there is a LOT more to this story than what they say. Theoretical numbers mean absolutely nothing, it is the actual performance that means a lot more. I said this once and I will state this again...


Disregard ANY information you may read about “Theoretical”, “Peak”, or “Maximum” polygon, pixel, texel per second or how GB/sec the memory bandwidth/bus speeds are, this information is misleading and systems will NEVER come close to realizing those numbers.

dunno if this guy is 100% right but alot of what he said makes sense....
 

Blackace

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