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PS3 Cell Processor 'Broken'?
D-Fly writes "Charlie Demerijian at the Inquirer got a look at some insider specs on the PS3, and says, Sony screwed up big time with the Cell processor; the memory read speed on the current Devkits is something like 3 orders of magnitude slower than the write speed; and is unlikely to improve much before the ship date. The slide from Sony pictured in the article is priceless: 'Local Memory Read Speed ~16Mbps, No this isn't a Typo.' Demerjian says when the PS3 comes out a full year after the XBox360, it's still going to be inferior: 'Someone screwed up so badly it looks like it will relegate the console to second place behind the 360.'" This is the Inquirer, so take with a grain of salt. Just the same, doesn't sound too good for Sony or IBM.
Microprocessor Online has some an interesting analysis. Pay attention to page 8, where the PS2 "Emotion Engine" processor is compared to the PS3 Cell processor. This is an analyst report for the industry of microprocessors.
If you really want to dig into the details of the Cell processor, check out Sony's resources. You have to agree to a bunch of things to get to the pdfs but there's a lot of information in them. Another place you can find information is IBM's resource site which contains a lot of stuff including the programming handbook.
My work here is dung.
there is no point in judgin a dev kit. x360 kits were shitty too.
[chinese democracy starts now
I'm aware that, in the past, The Inquirer has published questionable articles. However, they've certainly got a revealing picture to back it up here...unless they're outright lying and they photoshopped something, why should we take this story with a grain of salt?
ACs are modded -6. I don't read you, I don't mod you, I don't see you. Don't like it? Don't be a coward.
That Ken Kutaragi let his loser long-lost baby brother design the PS3 without looking at the thing or its price tag until it was unvieled?
Monstar L
So what is the difference between the local memory 16MB/s and the main memory 25GB/s 'reading'?
I assume the local memory is not going to be used much for 'reading' and only main memory is going to be used.
"Only one thing, is impossible for god: to find any sense in any copyright law on the planet." Mark Twain
Exactly. I'd rather have a console that has a 3-core cpu, 512 MiB memory, 20 GiB hardrive, and etherner ports. Oh wait...
Note: PS3 is a console for real men, Wheeee! is a toy for Linux-users and other faggots.
Not trying to flamebait here, but what is one of the OS's that will be running on PS3? Hint, it starts with L and ends with X.
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This reminds me, I am certain to be cruicified for not remembering this bit of trivia, but the PS3 is looking more and more like that car that Homer designed for his brother....
What was that called again?
On Wall Street they say "buy low, sell high" On the pad we say, "buy high, sell high" Isn't that somehow better?
On the cell processor, local memory is similar to a cache, but is not "transparently" managed by the CPU. Rather, the software must explicitly say what it wants to have in the local memory.
I thought we had all boycotted Sony anyway! Or are we on another bandwagon this week?
The subject says it all. It's getting really tedious. Why just not wait for the release and then make comments?
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Noticed the logo on the bottom left of the slide. Maybe it should have read
DeviStation
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The "Local Memory" is the memory attached to the RSX.
That the read performance for the Cell from this memory is dreadful is no surprise. This is exactly the same architecture that has been traditionally used in PCs. Reading graphics memory from the main processor is usually really really slow.
This memory is where you store textures and other graphics data. The main processor will usually have little need to read from this memory. If it does, then, as apparently Sony says, you just get the RSX to write to main memory instead.
This is a non-story. People have dealt with this for PC games for a long time.
I was just about to post the exact same thing. It amazes me that: /. editing kiddie troupe) seems to have no clue /., and it's constantly pointed out and constantly ignored
1) The poster had no clue
2) Zonk (and for that matter, the whole
3) This mistake happens _constantly_ on
4) Anyone with even a basic understanding of computers wouldn't make this mistake
Just more proof that "IT" != computer science
Does anyone ever bother reading the *IBM* documents for this? Never mind what Sony have managed to do to the cell processor, if you turn to the IBM CBEA developers handbook (page 75), you will see:
"Load and store operations (LS), 6 Clock cycles Latency". And that's the time it takes for the instruction to complete, not to be issued to memory.
(3.2Ghz / 6 cycles) * 16 bytes != 16MB/s
Personally, I'm gonna bet on IBM being right, seeing how they're the ones who made the bloody thing. I don't trust the inquirer anyway, but if those figures are true, the most likely answer is inefficiencies in their benchmarking programs, (Such as instruction starvation, a nasty side effect of using SPU's)
I've been hearing a lot of chatter about how the PS3 is difficult to program for, developers don't like it, Sony isn't providing quality libraries, blah, blah, blah. These exact same things were said about the PS2 when it first came out six years ago and it still managed to dominate its generation of console gaming. And it certainly wasn't true that developers avoided the PS2 in favor of XBOX or GameCube. As always the winner and losers of the console wars will be decided by the buying public, in the US, Japan, and Europe.
I think being too connected to the online debates about this stuff can make you lose sight of what the more average public thinks and bases their purchase decisions on. That's why the only real argument for the PS3's failure so far is the high price, not questions about performance or developer issues.
The The Inquirer article is rubbish and that slide is taken out of context. It seems to imply that the Cell can only read "Cell local memory" (whatever that is) at 16MB/s.
Memory transfer bandwidth between each SPU and its SPU Local Memory is something more like 25GB/s (gigabyte per second); sustained actual bandwidth between all SPUs is greater than 100GB/s; peak theoretical is greater than 200GB/s (assuming all 8 SPUs present for simplicity).
If you had access to the full version of the presentation (part of the full Sony PS3 SDK and technotes), you'd realise that that slide is part of a presentation about the RSX (the PS3's GPU). As such, when it refers to "Local Memory", it means RSX's Local Memory (eg graphics memory, video memory, VRAM or whatever you call it in fanboy/ps3/360-is-teh-suck websites). To be understood outside that context, the columns would be better labelled "Main System Memory" and "GPU Local Memory".
The Inquirer article seems to suggest that this figure of 16MB/s (megabyte per second, by the way, what the fuck is it with journalists swapping bits for bytes? why don't they get their shift/capslock keys fixed?) is some kind of show stopper. No it isn't. It simply means that the Cell processor has 16MB/s bandwidth when reading directly from memory-mapped GPU address space. So what? Unless you're planning on calling memcpy() or some shit to bring your data back then it doesn't really matter.
On RSX-initiated transfers you have 20GB/s bandwidth to do the same transfer (from RSX local to main system memory). Cell read bandwidth of GPU memory might as well have 0MB/s (ie no connection at all) and it wouldn't matter a bit.
About two years ago I decided to leave my post as a reviewer/tester for Sony. I had close ties with them for over 4 years and I began to have major misgivings on the direction and quality (lack thereof) that was being pumped out. I have been around the gaming industry long enough to know the beginnings of massive problems and they began a few years back.
Everyone close to me in the industry said I was crazy and that this would all smooth out and Sony would easily retain its market share if not grow more. I wasn't buying it and stuck to my guns, I'm pretty happy about my decision almost daily since day 1 of E3 this year.
I was against UMD from the beginning, yet everyone claimed that the sales were stellar. Looks like they weren't and they are proprietary, expensive, unwieldy little discs that no one wants to deal with. The "cell" processor was without a dobt my turning point, I have ZERO faith in it or the architecture and it will not become this ubiquitous omnipresent processor as so many claim, even IBM has major problems with it and designing compilers and dev software for their own product. Control schemes have been radically changed from initial proposals, and too quickly to be properly tested... that is a bomb yet to go off. System price and dev costs that are just too high for our current economic situation as well as for widespread adoption. There are more issues, but top it all off with a new unproven media that is also expensive and offers no real consumer advantages and you have the high risk of a catastrophic failure that could hurt Sony and IBM even more than they are already hurting.
The best that can happen is that companies finally lose the DRM/proprietary/Closed nature of their consumer electronics. Stop treating customers as criminals and start to offer them affordable and accessible entertainment that is convenient. I'd actually prefer consoles to standardize and become built into consumer electronics so that developers and consumers can really get to work on a stable and long lasting platform. Imagine the possibilities. There is a lot to be said for standards.
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And it turned out to be one fo the most successful consoles ever.
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This isn't the online IT arm of the National Enquirer, you know.
The Inq isn't always right, but what the do tend to have is a lot of news-breaking stuff that they're (well, Mike) is willing to publish regardless of the consequences when the corporate heads find out there's a leak. Thats' why Mike got eased out of The Register when it went more corporate to form the Inq in the first place.
Those who have been following it for a while will remember all the appearances of leaked memos from Compaq (ex-DEC) insiders who were willing to leak happily to someone of the old school who was interested in seeing how the whole fiasco was turning out. Compaq/HP even started internal witchhunts looking for the leakers.
Regardless, the only real problem people might have with the Inq is they can't distinguish between an opinion piece and direct reporting, or can't accept that while the information as presented might be correct, it doesn't ensure that interpretive parts also follow.
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"The "Local Memory" is the RSX graphics memory. The Cell shouldn't need to read this. The PS3 would still work even if the Cell couldn't read this memory at all. This memory is where you store textures and other graphics data."
IMO it's reasonable to have asynchronous communication with the graphics subsystem. The only stupid thing going on is calling graphics cards memory "Local Memory". It suggests that the X-Box got it right by having one big chunk of memory that is read by both the CPU and GPU even if most developers will make the same basic split anyway.
"The "Local Memory" is the RSX graphics memory. The Cell shouldn't need to read this. The PS3 would still work even if the Cell couldn't read this memory at all. This memory is where you store textures and other graphics data.
Presumably in the (unlikely?) event you did need the output from the RSX graphics chip for manipulation by the Cell processor gubbins, you could get it to render to main memory, let the processor do the appropriate data-diddling, then have the RSX read it back again?
The 'local memory' is presumably the RSX's private play area, and thus the RSX gets maximum-stupendous-speed priority, and the Cell gets occasional access at weekends. Which is a bonus, and not even necessary...
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Sadly, you are also wrong.
In the slide, the "Local Memory" refers to the RSX local memory, not the SPU local memory. The article says that the next slide is Sony telling devs to use the RSX to do the transfer instead, which only makes sense if it is talking about the RSX memory.
Your conclusion is right though, as this also is memory that the Cell doesn't need to read from.
Yes, in fact the article quotes the next slide as saying "Don't read from local memory, but write to main memory with RSX(tm) and read it from there instead" which is exactly what you suggest.
Yes, but on the other hand, the PS2 games don't look anywhere near as good as Sony claimed they would. Remember the claims that in PS2 games individual hairs on a persons head would be modelled? Both the GC and Xbox games generally have better graphics than PS2 games.
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Lynx OS?
Software sucks. Open Source sucks less.
After reading the article, I realize that these are numbers for Cell and RSX local memory. Of course, our stupid submitter wanted to make us think this was the SPE's local memory, and purposefully put a DIRECT LINK to the photo in addition to the article link when he knew it would be taken out of context.
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And occasionally whores for Karma.
Either that, or a broken benchmark. Each Cell processor (Synergistic Processing Element -- SPE) shares its instruction fetch port with its data memory port. The SPE can buffer up 80 instructions at a time (2.5 fetch words), plus an additional 32 from a branch target. Fetch will stall if the memory system gets saturated with loads and stores. Properly written memory-intensive code includes explicit fetches to keep these buffers full. Incorrectly written code will cause problems. Still, that doesn't explain a 3 orders of magnitude drop.
If you look at the slides on the page I linked to above, you'll see the SPEs are not connected into the global address space. They connect to a private single ported memory, and to each other through two unidirectional rings. (The ring structure is not apparent from that diagram, but trust me, it's there.) These rings then connect to a DMA engine.
If you wade through this paper, you'll see that the Cell compiler implements a software cache. (The same paper also explains the instruction fetch mechanism mentioned above, BTW.) That is, it emulates a cache in software, using the DMA to actually move memory around. Depending on the nature of the benchmark and how it was written, it could be that the read benchmark spends all its time allocating stuff into this cache and waiting for it to arrive. Writes would be faster because the cache can "write behind" without having to wait for the allocation to happen, if the compiler is smart enough to know that the previous data will be entirely overwritten. So, if the benchmark goofed, then the results are meaningless.
Fact of the matter is that the SPEs are capable of reading 128 bits a cycle each (128 bytes / cycle across the 8 SPEs). Other benchmarks, such as the article recently posted to Slashdot about using Cell for scientific computation confirm that this thing hauls--and these are bandwidth-intensive tasks. The quoted paper did run some numbers on real silicon and showed numbers similar to their simulation results.
With all this in mind, I find it hard to believe that Cell is broken.
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512 MiB
Well theres your problem, fitting 512 Men in Black into any console is going to cause heat problems. . .
Can I get an eye poke?
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