Shiftings in Architectures

Cell, the hype

Sony is working on a new kind of processor which they call Cell. A single Cell processor is said to have a 1/75th of the power of the Blue Gene/L supercomputer in teraflops, and that for 400 dollars.

The new Cell processor is hyped, a lot. People are shouting that the performance of the PlayStation 3, which will feature a Cell processor, will blow away those of the competers: the XBox and the Revolution, both using claimed to be slow PowerPC processors.

Teraflops

So what are these Teraflops? Why aren’t they talking about Hertzes anymore?

A TeraFLOPS stands for 1,000,000,000,000 Floating point Operations Per Second. (TeraFLOPS on wikipedia).

A normal computer has a few GigaFLOPS (one TeraFLOPS is 1000 GigaFLOPS).

The Cell processor in the PS3 will have 1,8 TeraFLOPS. It is very easy to believe that the PS3 will inheritly be about 500 times faster than a normal computer. But that is false.

The performance of a computer isn’t all about how fast a computer can calculate with floating point numbers. The performance of a computer has got to do with a lot more than that. Simply doubling the memory performance (not specificly memory bandwidth, but the whole) would have a bigger impact than doubling the amount of TeraFLOPS, even on applications that heavily rely on floating point operations.

So why have a lot of TeraFLOPS then? It is quite simple, the new platforms haven’t got seperate GPU’s (Graphical Processing Units), their task is now intergrated into the CPU. And what was their task? Calculating, a lot, with floating points.
The amount of TeraFLOPS on the new platforms are the sum of the amount of TeraFLOPS of both the GPU and the CPU. A GPU needs to calculate a lot with numbers for 3d rendering.

Your normal computer has got a lot more than those few GigaFLOPS in your CPU in your GPU already. Although the leap to over the one TeraFLOPS is certainly impressive.

Marketing

Super Computers need to do a lot of FLOPS too, they calculate models which got a lot of floating points. So why put the Cell processor in the Ps3 instead of directly in some supercomputer? Simple, marketing. Almost everyone that is superficially following the computer news is telling me over and over again that the Cell processor is the most incredible thing there is. It is hyped.

Linux on Ps3

Also the Cell processor uses a whole new architecture which still has to be tested a lot to mature. Sony will let you install Linux on your Ps3? Why? Simple, because they want the Linux community to add decent support for the Cell architecture.

New Architectures & CLI

I guess it will be a matter of time before new architectures will come. A problem with a lot new architectures is that there isn’t a lot of support for them yet. The solution? CLI’s like Java and .Net could bring the solution.

Microsoft rumoured to have MSIL running (semi)natively on their XBox360 and making Longhorn more and more rely on .Net (the ontop applications, not the kernel offcourse) means a lot less architecture dependency.

I wonder what will happen, but one thing is sure.. things are shifting.

2 thoughts on “Shiftings in Architectures”

  1. Sony’s ps3 and microsoft’s xbox DO have separate graphics subsystems.

    There’s been some confusion around the TFLOPS theoretically available in the PS3. Sony quotes a complete system throughput of 2 teraflop. however, the 1.8 teraflop are the GFX card, not the cell… cell is supposed to have 218 gigaflop; and even this number is ridiculous, because it’s obvious that with such a limited architecture, there’s not much that’ll run anywhere near that many flops of usefull instructions on the cell.

    Doubling memory bandwidth doesn’t add more performance than doubling flops (as example, take the well known benchmark superPi); and anyways, the cell has been architected with local memory and the like to try and circumvent the bandwith problems somewhat. Obviously you need an architecture without screaming bottlenecks if you want good performance; however, memory bandwidth isn’t the bottleneck many people think it is because cache sizes have increased significantly (and in cells case, you have the local memory).

    If I understand correctly, then the linux-on-cell isn’t sony’s thing, but IBM’s, which makes sense as it’s natural for IBM to want to use these things in scientific computing and the like in future machines.

    I think the cell is the best invention since sliced bread (well…) – but not because it’ll blow us away performance wise, but because it finally marks a real step in an architechtural shift that’s been a long time coming.

    Oh and btw, microsoft is using .net a lot less in longhorn internals than planned, the speculation being because of performance problems. .net will remain the api of choice however, it’s just that the actual code cruching internally with be “unsafe”.

  2. Thanks for the correction(s) 🙂 corrected them in my post, thanks again

    There seems to be a lot of conflicting articles, posts and emails everywhere.

    With memory performance I didn’t aim specificly on bandwidth. I meant the overall speed of memory usage, whether this is increased due to more or better l2 cache or just faster memory. A modal application and OS relies a lot more on memory operations than on floating point operations. Offcourse specific applications use floating points a lot more.

    In my opinion the architecture doesn’t really matter, but the layer on top. Although I think it is great that there has been some movement in the market.

    I didn’t mean the windows ‘kernel’ but rather the not-architecture-specific stuff on top like for instance the desktop and the explorer which will be rewritten in .net. Microsoft old plans to do almost everything in .net were just not practical enough.. and they took too long like the rest of their .net inovation.

Leave a Reply

Your email address will not be published.