Slashdot Mirror
Cell Architecture Explained
IdiotOnMyLeft writes "OSNews features an article written by Nicholas Blachford about the new processor developed by IBM and Sony for their Playstation 3 console. The article goes deep inside the Cell architecture and describes why it is a revolutionary step forwards in technology and until now, the most serious threat to x86. '5 dual core Opterons directly connected via HyperTransport should be able to achieve a similar level of performance in stream processing - as a single Cell. The PlayStation 3 is expected to have have 4 Cells.'"
Something that has always confused me in gaming consoles is that, despite incredibly powerful hardware (processors, graphical chips, etc.), the system developers seemingly always neglect to put in enough RAM for most games to perform to their potential. Many PC ports often have portions compromised due to the lack of RAM, and system speeds also suffer because of this.
Seeing how RAM is increasingly becoming cheaper, is it possible that new systems like the PlayStation3 might be able to provide RAM that actually allows games to reach their potential along with this new cell hardware?
I'll believe it when I see it. Sony made outrageous claims with the PS2 in the year or so before launch, I see no reason to believe this will be any different.
On paper an Emotion Engine was supposed to destroy everything, but achieving maximum throughput was difficult and other contraints such as I/O and memory hampered performance. Programmers had to learn a very different way of programming to make full use of the processor and it's two vector units.
A Cell might be a killer chip on paper, but real-world hardware with I/O latency and memory contraints will bring things down to a more reasonable level. Don't forget that multiprocessor programming is *hard*.
Hopefully, developing software for Cell chips will be easier then the early days of the PS2, Sony has already said as much a few months ago.
Quotes from article:
"GPUs will provide the only viable competition to the Cell but even then for a number of reasons I don't think they will be able to catch the Cell."
Did this guy forget that NVidia is designing the GPU for PS3? If Cell is so almighty, why does Sony uses NVidia GPU instead of using more Cells for graphic prosessing?
"There is another reason I don't think Nvidia or ATI will be able to match the Cell's performance anytime soon."
Of course, Cell based products won't be available anytime soon either. According to the current rumors, PS3 will be available in Japan in Spring 2006 and elsewhere in Autumn 2006. One and half years equals a generation in the GPU world...
I love this kind of articles where some future products are compared against current ones and declared as a clear winners...
I'm willing to believe that a 4.6 GHz chip with 8 ALUs and high bandwidth memory would be fast, but even in bulk, there's no way they can afford to put 4 of them in a sub-$500 game console.
I've been reading PR about the Cell for years, and nothing I've ever read has seemed even remotely plausible. Is there any objective information that even comes close to substantiating any of these claims?
While I tend to agree the Cell is an impressive architecture, this article is a steaming pile of B.S.
No cache for CPUs? A breakthrough? Hello! Both PSone and PS2 have the so-called scratchpad, which is what the Cell seems to have: a cache which has to be managed explicitly by the programmer. Breaking news: This is a royal pain in the ass. And calculating bandwidth when reading from this tiny scratchpads makes about as much sense as calculating the speed at which a x86 processor can execute MOV EAX, EBX.
Magically "the OS solves everything", and, in an obvious attempt to automatically get OSS-crowd support (is that "slashdot-trolling" or "slashdot-baiting"?) the triumph of Linux is predicted, because it's portable. Good luck getting the Linux kernel and GCC compiled, let alone running well on a massively parallel array of tiny CPUs without cache.
You have not read it. It will be on a specific class of tasks. It is similar to modern GPUs. They are faster then 10 opterons on a specific task.
Back to the article. The guy seems to understand hardware, but he does not understand shit about software. Once he got past the first 3 parts he started babbling. Linux on cell, so on, so fourth. If he just read his previous parts he should have hit himself on the head. The only type of linux this can run is mcLinux. There is no memory protection as such. So no Linux, no Windows past 2000, no MacOS past X, so on so fourth.
Similarly, it is all nice and well about cell software beasties making herds by themselves and cooperating on a task. I am going to be a spoilsport and ask a nasty question: Err.. What about a security model? Memory protection? Privilege model for communications? So on so fourth...
To continue on this, the power of a modern general purpose OS is the task switching. How long does it take to load and store the context of the vector processing units? Doing so requires moving their dedicated memory to main memory. This will take ages.
Overall, this is a design similar to Cray 1 initial design. Cray initial design smashed the IBM, DEC (and lesser fish) monopoly on big computing iron to bits. Unfortunately the next thing the people buying the Cray asked for was "can we share this resource between two people?". The answer was provided eventually, but by the time Cray could do all the nifty time sharing and memory management tricks necessary to do this its advantage was no longer phenomenal. And all people who could use Crays for single tasks with manual scheduling actually continued to use it that way. But it did not even dent the general purpose big iron market.
Baker's Law: Misery no longer loves company. Nowadays it insists on it
http://www.sigsegv.cx/
Nicholas Blachford is an idiot. Do not read any of his articles. Just to give you the best of Nicholas, read his antigravity article and visit his web site:
;)
http://www.blachford.info/quantum/gravity.html
Also, look at the nose pictures of him
http://www.blachford.info/other/me.html
Seriously, the guy has burned most of his sane braincells.
For serious laugh, read his article series 'building the next generation' from osnews. I really got good laughs from that 4 part series.
Also, it didn't take long to spot a totally idiotic statement from todays slashdotted article:
> Parallel programming is usually complex but in this case the OS will look at the
> resources it has and distribute tasks accordingly, this process does not
> involve re-programming.
Here Nicholas misses the core problem of parallel programming. The program algorithms _always_ have to made parallel. The OS can't do it.