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Under the Hood of the Xbox 360
An anonymous reader writes "IBM DeveloperWorks is running a behind the design story for the making of the Xbox 360. The 360 has but a single chip with 165 million transistors for it's CPU " From the article: "This chip is in fact a three-way symmetric multiprocessor design. The three PowerPC cores are identical, except that they are physically reflected through the X and Y axis. Each of the CPU cores is a specialized PowerPC chip with a VMX128 extension related to (and partially compatible with) the VMX instructions in the G4 and G5 CPUs. The three CPU cores share a 1MB Level2 cache. Each processor has 32KB each of data and instruction Level1 cache. The chip's front-side bus/physical interface has a 21.6GB/second bandwidth, and runs at 5.4GHz."
But for the custom motherboard, custom CPU, custom GPU i guess
"The way we can tell it's C# instead of Haskell is because it's nine lines instead of two." -- wadler
Actually, no.
A big cache is good when you are dealing with programs that could access ANY data at ANY time (or you're running multiple programs). With games, that doesn't really happen. Game code is sort of "linear", and you're only running one at a time.. So the cache can be filled with what needs to be there, and nothing else.
Microsoft also has a history of buying out top software companies and pushing the rest out of business through anti-competitive practices. Sony at least keeps their competition afloat.
Good point. Atleast Sony only puts root kits on their customers computers, which can cause them to be infested with spyware and who-knows-what-else.
Which is about as interresting as hyping Intel's 4GHz pentiums.
No one gives a flying fuck about the raw performances of the machine, high definition is not for consoles anyway (hint: my computer yields above twice "HD"), blu-ray blows (not the least because it uses Java as a "mandatory part of the standard).
Three things really matter for consoles:
Now please take your PS-fanboyism back to the Sony board, the numbers will speak when the PS3 is released, until PS3 is live it's mere FUD and vapor wall.
"The way we can tell it's C# instead of Haskell is because it's nine lines instead of two." -- wadler
Much like Duffman, Sony promises lots of things. There were a lot of features that were supposed to be available on the PS2 that just never ended up in the final system. Not wanting a 360 because it's not that much an improvement over the current XBox is good reasoning. Not wanting a 360 because you just bought a new console a couple of years ago is good reasoning. Not wanting a 360 because of all the things Sony claims will be on the PS3 is just silly. We don't know the "Top 10 reasons for a PS3" because we don't know exactly what the PS3 is yet.
Also, while the Revolution's controller does pose some unique possibilities for gameplay, it's only a controller. Any of the modern gaming consoles could implement such a controller. If it's that big a deal, expect MS and Sony to have their own versions by the end of 2006.
Neither of those points should have any impact whatsoever on whether to buy an xbox360 or a PS3. If you like playing console games, both systems are sweet. If you have to choose one, it's probably because of a game avaliable on one system and not the other.
*sigh*
People, think a little. Sony is a mega corp, and has its fingers in a shit load of businesses. The music business is separate from the Playstation business, and in fact, the Playstation business is supposed to be the biggest breadwinner.
The music division screwed up.
If the Playstation division continues to be successful, which division's vision will win out?
The division that got the world steamed at them, or the division that brought you Linux to the PS2?!
In other words, you want to *support* the Playstation division, while giving the music division the (figuratively) bird.
-B0fh
How is it a miracle when this is exactly what's been happening with consoles for many years?
NES looked better than nearly any computer of its day. Ditto Genesis and SNES. Playstation and N64 packed an incredible amount of power into a cheap bundle. Remember the hype about PS2's Emotion Engine? There were rumors that exporting it would be restricted because it was going to be classified as a super computer. People were saying Iraq was going to use it to guide missiles. Xbox literally was a cheap PC, but gave more bang for the buck than your average beige box.
Consoles do this by taking the right shortcuts. They have a very focused performance target for very specific tasks. No need to add anything more than the minimum. Plus, they sell more than nearly any OEM PC maker so they get good prices on the parts.
The global economy is a great thing until you feel it locally.
Anyone who thinks it crashes regularly or that more than 1% of units are overheating is simply a moron. A lot of people here seem to have a fixated fantasy that they are so desperate to believe that they ignore the facts. The fantasy basically consists of that MS has rolled out an overheating worthless machine that when not overheating 95% of the time is crashing. Get real, I'd imagine the failure rates for units are about the same for any piece of consumer electronics.
Ferfuxsake dude, why don't you chime in when you have something other than baseless speculation to combat the baseless speculation? Just a thought.
You forgot the most interesting option...
- The Nintendo Revolution
I don't want to sound like too much of a fanboy, but what can these consoles really give me that my PC can't? I'd rather have a console thats sole focus isn't trying to outpace my PC in terms of graphics... but to push the limits with new controllers, unique games and not costing me my 1st born child or my left arm to acquire.
Uh oh guys, there's an honer stewdint in our ranks.
If even 1% of them do crash consistently through regular usage, that is a spectacular failure. Gaming consoles are regarded as "appliance" type devices. They should have tested that it could run a stress-test (or PGR3, whatever) for a week without crashing, and if they did that you would expect that the number that couldn't even survive for 5 minutes would be significantly less than one percent.
With a console during its "lifetime", all of the important hardware is a known quantity, and all of the software has an opportunity to be tested before being given a shiny sticker. There's no reason that the damn things should be more liable to crash than certain other products from Microsoft. None at all. It's just not the same thing.
But mentioning live as the deciding factor is ignoring history. The x-box had it and it didn't sell. Nobody has ever in my opinion come up with a satisfactory reason for the failure of the x-box. The gamecube is easy. It just didn't have the right image. While I thought about 1 or 2 games as worth playing that was it. The rest I considered to cutsey and consoly for my tastes. I don't mind this on my handhelds where it actually helps (don't want to scream like a girl playing fear in public) but not at home.
Another one that amazed me is that one post said the x-box had signed the big names. Bungie and EA. Wtf? Bungie IS NOT a big name. They got 1 game and that is it. EA is big but EA signs on to anything. Getting EA to endorse your new console is like getting a hooker to go out with you for money. Even /.ers should be able to manage that.
The only real advantage that MS has over both Sony and Nintendo that MS doesn't have to win the money race. They can afford to loose money on this generation and the next and the next.
As for the graphics being amazing. Oh please. I already play at higher resolutions on my now 2yr old PC. Richer friends won't accept anything less then 1600x1200 while sony's own games like eq2 can already make use of 512mb video cards despite the fact they were not even out. Other recent games to can make use of hardware features that even top of the range pc's don't have let alone these weak consoles.
I still remember console fans being excited over star fox while I was playing x-wing.
No saying that anyone is going to win the current battle is insanity. The 360 is lacking launch titles and has not got the mindshare with the general public. The PS3 is an unknown quantity and Sony's reputation might be damaged (but this should equally have counted against MS with the X-box) and Nintendo seems to try another gamecube wich didn't work well the first time. The PC (often not counted) has such titles as WoW wich simply cannot run on any of the consoles yet is a huge earner for its parent company. Oh and has all that live crap except at no-charge.
Frankly I find these discussions very amusing but only as an outsider. I remember people defending their console in each of the battles and use the same arguments regardless of the wether they made sense before.
Console fans are like generals. Always willing to fight the last war again regardless of the outcome.
MMO Quests are like orgasms:
You may solo them, I prefer them in a group.
Agreed, the price is a big stopper for some people and, I also agree, there are not a ton of must-have games on the Xbox 360.
:)
However, it does have Perfect Dark: Zero, Project Gotham 3, Kameo (don't knock it 'till you try it) and soon, DOA4 and Battlefield.
Battlefield + Xbox Live = Heaven.
Granted, I don't know a whole lot about what games are coming soon to the Xbox 360 for lack of time, but by the time the Playstation 3 comes out, Xbox 360 will have a lot more games by great developers and I'm going to venture a guess and say the premium system won't cost as much as the PS3 will.
That was my point, was that waiting for a PS3 was stupid. You get less (no unified online service, which is a BIG, BIG portion of why you should get an Xbox 360 over PS3, no titles from Rare or Bungie) and get some things that are somewhat unpleasant (blu-ray: Who really wants a disc format that can brick your system of the manufacturer tells it to? How long before it's cracked and a virus is written? Who really would be angry about getting up every few hours to change a disc? Big deal. None of us had problems with it in the PSX days.)
Just forget for one second that Microsoft makes the Xbox. It's one of the products of theirs I really, really like and is well put-together by a great team.
Go Microsoft?
-Eric Smith
Just to point out 1% = 1 in 100 machines
1/100 * ( MS Release ) = a *lot* of stations. And with a shortage already, getting a replacement may not be quick.
1% is no small stat when mixing with large volume.
And for an hard-to-get, expensive appliance, it's not very good odds.
Who wouldn't? Wouldn't you like a 100mb cache? Hell, wouldn't you like all of main ram to actually be as fast as an L2 cache?
This is a game console, not a multi-tasking general purpose PC. This is reflected in both the power a programer has over the hardware, and it is reflected in the fact it depends on the programmer to make up for cost saving measures implemented in the hardware.
You're thinking about thread scheduling the way a general purpose PC would schedule threads. It doesn't work that way in a game system. When talking about threads on a game console, we're talking about hardware threads. The programmer decides what core runs what logic, when it runs that logic; there aren't any context switches, and threads don't "change" cores when running.
The cache design on this chip is actually quite cool. If you're only going to use a piece of data once (or infrequently), you can instruct the processor to not store the data in the L2 cache (leaving data that you're using more freqently in the cache). Additionally, the L1 and L2 cache can hold separate data, and a load into the L1 cache doesn't require a storing that data into the L2 cache. When writing data out to main memory, a program can instruct the processor not to store it in the cache. Software can also reserve chunks of cache for whatever purpose it wants. Finally, a direct link between the CPU and the GPU can be established where the GPU reads data directly off of the L2 cache as the CPU generates it.
These abilitys make it possible to utilize L2 cache better than you would with any general purpose PC. However, it requires more thinking and more effort to do so. That's the price/performance tradeoff you get.
An inability to execute instructions out of order does not prevent PPC code from running, nor is it crippling. Additionally, having an instruction window is rather pointless when instructions can't be executed out of order.
You don't need these things with properly compiled code. But that's the trick; you can't take poorly compiled code and expect it to be performant.
Traditionally general purpose CPU's need the capability to execute out of order because they're running code that wasn't written for their current design -- they have to run code designed to run on x previous iterations of the processor. And traditionally, CPU manufacturers like to tout how their new processor runs x benchmark 50 times faster -- and they can't do that without out of order execution.
Anyway, there are reports that only one core is availble to intitial game developers, and one of the cores is strictly for M$ bullshit content protection TC such as the hypervisor, etc.
"Reports", yeah, but this isn't true. Several of the lanuch games were multi-clore, including Kameo and Perfect Dark. Numerous developers have commented on this. And as far as I know, Hypervisor on IBM systems has nothing to do with content protection and it's difficult to see why it would be implemented here.
Sounds like a shitload of TC shit build right into the chip, so I am NOT holding my breath for linux to be ported to this (not that I wouldn't be thrilled to see this).
Why? I'm being serious. What is the point? Most people agree that the 360 is FAR less of a GP design than the original XBOX, and it's using a funky architecture, so it's likely that it will be difficult to get Linux or *BSD to work, it'll probably perform like crap, and you'll have to re-compile everything for the 360. What is the value proposition here over a cheap PC? I can buy $200 PCs without OS from Fry's.
I can vaguely understand the Linux projects for the original XBOX. That was basically a PC, and it was easy to adapt both Linux and software. This isn't true with the 360. Look at the PS2, Linux on the PS2 is all but useless because of the different architecture. I tend to think the original XBOX will be regarded as UNIQUELY hackable in the world of game consoles.
Now imagine having to write your code in such a way that it can be split across 7 processors.
If you first structure your game loop as a dataflow diagram, you'll see more opportunities for parallelizing your code. Figure out what depends on what, and if two things don't depend on one another early in the computation of a given frame, you can run them in separate threads on separate cores with little or no penalty. Many tasks in a game program are in fact embarrassingly parallel. For instance, if you have twenty different procedural meshes to generate, such as a tree or a character's draped clothing, generate one on each core until they're all generated.
The CPU cores do not support out of order execution. This means that the processor will be more likely to blow extra cycles when used in an unoptimized environment (as on a desktop PC).
Out of order execution is useful primarily when running code that's optimized for a different microarchitecture that has a different pipeline structure (such as running P1, P2, or P3 code on a P4 or Athlon). Given that all games will be compiled specifically for the Xbox 360, the compiler will have little or no trouble reordering instructions to fill both pipes of an given inorder CPU. And if they do manage to crack the Xbox 360 and install a Linux distro, then Linux, glibc, X, and Free apps will be recompiled specifically for this CPU.
The thing would be slow as molasses if you tried to run PPC code that wasn't optimized for this design change.
I'm not arguing that is false. I am arguing that your original premise -- that the unit is incapable of running general purpose logic efficiently -- is false.
I am of course ignoring the "it could run OSX" arguement, because that is never going to happen. But it is hardly a crippled processor incapable of performing every day tasks.
You aren't going to be dropping a random linux kernel on the box; you're going to recompile for the hardware you're running on. It hardly has to be insanely specialized, nor is it limited to some niche number crunching role. You just have the feed the processor well organized code.