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How The 360 Works
The always informative How Stuff Works site has an article today entitled How the Xbox 360 Works. From the piece: "The other interesting thing to note about the Xbox 360 CPU is that each core is capable of processing two threads simultaneously. Think of a thread as a set of instructions for a program's job. The core processes these instructions and does the heavy lifting to get the job done. A conventional processor is traditionally capable of running a single execution thread. Because the Xbox 360 cores can each handle two threads at a time, the 360 CPU is the equivalent of having six conventional processors in one machine."
I thought something like 15% of Xbox's *didn't* work. Source? Slashdot. Surprise, surprise. It's funny. Laugh.
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"Because the Xbox 360 cores can each handle two threads at a time, the 360 CPU is the equivalent of having six conventional processors in one machine."
No it isn't.
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Because the two threads in the chips share arithmetic and floating point units and whatnot, they get best case throughput of 1.3x a single threaded chip. This is according to Sony who has the same PPU on their PS3.
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All the CPUs have to share access to memory, especially if one CPU is locking part of the cache for a big signal processing job. The bottleneck at the memory controller keeps SMP (symmetric multiprocessing) from reaching its theoretical throughput.
In order to get true performance out of a multicore system, you have to use NUMA, which is not just part of the hook from a Romanian pop song. It stands for non-uniform memory access, and it refers to associating a physical memory chip to each CPU. It's "non-uniform" because it takes longer for a CPU to read or write another CPU's memory than to read or write its own. But running threads that don't need to communicate too much and putting their memory on separate cores does ease up on the memory controller bottleneck.
Wonder if How Things Work got paid for that?
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That's how it works? And here I thought it was just the latest console using Hype technology.
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After reading the how the XBox 360 works, I checked out a couple other systems.
.999 teraflops?
None of them had any details about how any of the systems actually worked; it was just a list of marketing bullet-points and features published by the manufacturers.
How does knowing the system's launch lineup help me know how it works, anyway?
As for things that were flat out wrong about the 360...
9 billion dot products per second? Are they claiming that each core can compute a dot product at nearly every cycle? And if so, how is that number helpful? You still have a ton of other stuff to do in a game engine besides just computing dot products.
1 teraflop? Each thread on each core can calculate 166 billion FLOPS? Oh wait, you mean that you're also counting GPU performance in that number, which accounts for probably
500 million triangles per second... With how many textures applied? How many light sources? Oh, zero textures, using flat shading, with no light sources? And all 500 million triangles are part of a single triangle strip and are each 1 pixel in size? And that's just the theoretical maximum anyway?
What a worthless site. I feel dumber for having read it.
--Jeremy
Jesus was a liberal
I swear, Bill Gate$ and his cronies are definately pulling all the propaganda strings on this one. I'll admit, I'm a fan of the XBoX, but not of it's 360 counterpart. I believe that the console was rushed out the door as fast as possible with enough marketing pusking behind it to possibly sell it as the next Messiah of console. The damn thing CRASHED when it was released, I don't care how wowie-zowie it is. That means one thing to me, it's broken on delivery. Now sadly, I'll have to find a different console to play on. I'm not buying a PS3 because of the Rootkit problem Sony just had, and with the 360 fiasco.... And why isn't Nintendo capitalizing on this? I'm sure they've still got SOME life left in that corporation.
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That talk kinda makes you cry, doesn't it?
That's right..cry those nerdly tears
It's like a reflex action to bash Microsoft here. First off, quality is always shaky on the first batch of any gaming console. It's a business where the hardware launches are historically tight. The only company that releases solid, well built, well tested consoles at launch is Nintendo, and look where their share of the market has gone. Second, based on everything I've read about the XBOX 360 it has a solid, almost textbook design, for the best technology of the next 5 years (multi core processor, unified pipeline shader/vertex on the graphics card, etc). I see alot more to question about the PS3's cell (limitations of SPE's etc) & the late addition of NVidia, since Sony only pulled them into the PS3 when they realized the Cell wouldn't be able to do the GPU work. Need I remind everyone that you are bashing a 3-GHZ G5 w/ 3 Core's paired with ATI's finest and all for $400? Yes, the marketing BS is just that, but if this was anyone else's product it would get treated alot better.
Now really, if you're reading this site, you should know what a thread is, for pity's sake...and if you didn't, now you certainly don't because that's not a good definition.
Should popular mechanics explain what a combustion engine is? Is this news for nerd-wannabes?
Advice: on VPS providers
The Onion has a summary that is just as informative and much shorter.
Don't you have someone you'd die for?
At the end of the day, all of this talk about threads in these processors will be a wash. In fact, I'll bet that most titles won't take advantage of it. Developers will find this to be a real pita to program and will cost them a good amount of time and money. It all sounds great in theory, but thats just theory. At the end of the day, people will realize that these machines are not super computers and their benefits will be outweighed by their cost.
So what, if it still just crashes? In fact, this might be one of the reasons. Why can't M$ "innovate" (i.e. play catch-up with the real innovators) somewhere safe first? Wait, that's exactly what it is! Everyone else innovates first and goes to market second. M$ goes to market first, and does alpha testing in public, that way they're usually only slightly beyond and appear innovative.
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