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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."
No, it really isn't. The original XBox was. The 360 has quite a lot of custom technology inside it.
"The dew has clearly fallen with a particularly sickening thud this morning"
PowerPC's mainly an IBM-designed and promoted architecture, borne from the Apple-IBM-Motorola alliance.
Apple are simply one of IBM and Motorola's (now Freescale) customers.
What's the frequency, Kenneth?
Didn't RTFA, about the design of the custom processor, did you?
I thought Power PC was the mac? Why did Microsoft pick apple CPU's for their Xbox? Is Intel falling out of favor?
The Power architecture is an IBM design intended for use in their large server machines. About the time that Motorola was struggling with producing better/faster 68000 chips, IBM designed a cut-down version of the Power chip called "PowerPC". Apple adopted PowerPC from IBM, thus leaving Motorola behind. However, Motorola realized that they were losing big business and licensed the PowerPC architecture for manufacture. Eventually, Motorola couldn't keep up and Apple started using IBM for the higher end chips. Thus Apple now uses a combination of manufacturers to get their PowerPC chips from.
The chip itself has nothing to do with Apple other than being their preferred platform.
Javascript + Nintendo DSi = DSiCade
This is probably a JTAG block. Depending on what it's built for, you get:
- instruction single-step
- register and memory peek/poke
- control suitable for burning on- and off-chip flash/eeprom
- trace buffer that contains the most recently-executed opcodes
- breakpoints
- access to profiling and instrumentation registers
JTAG is a serial protocol that runs much, much slower than the core -- but it's an extremely nice way of getting into a running chip and poking around.
It's probably the JTAG debug logic. Most modern CPUs use a JTAG port (full-duplex, multi-device serial port) to provide access to internal CPU state, as well as providing hooks for starting and stopping the processor.
/ 3675.html
JTAG is a hardware test standard, but chip vendors define their own extensions to it to provide software debug hooks. Most PowerPC chips use what's called the Common On-Chip Processor (COP), which is controlled through the JTAG port. The specific details of COP and its implementation on each chip is proprietary, and usually only available to IBM, Freescale, and a few select tool vendors with NDAs. Here's a link to some more information on PowerPC COP:
http://www.elecdesign.com/Articles/ArticleID/3675
"PS3 will have better graphical performance, up to 2x. High definition. Blu-ray. Up to 7 wireless controllers - those actually mean something. Xbox 360, will just have improved graphics over the original Xbox."
Who says the PS3 will have two times the graphical performace? Speculation does, perhaps.
The Xbox 360 is high definition out of the box.
The Xbox 360 does NOT use proprietary disc formats that can, at the vendor or manufacturers will, brick your box.
WHO NEEDS SEVEN CONTROLLERS ON ONE BOX!? Jesus. What average Joe with a TV is going to be able to support seven players? Maybe the rare Super Smash Bros. style game, but nothing big.
The Xbox 360 has several things the PS3 does NOT have:
1) Xbox Live. The Playstation 3 has no unified online service at all and has no plans to. Xbox Live is an awesome way to play your video games online. One fee. No ten bucks a month here, five bucks a month there... $50 a year.
2) Time. Xbox 360 is here now whereas the PS3 is going to offer comparable hardware and games in a year.
3) Developer backing. Bungie and Rare are both developing for the Xbox 360, and that's only naming two big name developers. Also Final Fantasy will be coming to Xbox 360 too. EA is also signed on.
The question is why NOT buy an Xbox 360? Would you rather wait and get less for the same, or maybe more, amount of money?
-Eric Smith
You'd think that when dealing with high throughput graphics applications, a larger cache would make far more of a difference than a few hundred MHz either way.
In fact, no. Think of the PlayStation 2 and its graphics, it has just 16+8Kb of memory cache.
Caches have very little work to do in a vectorial enviroment, while your Sparc is a server CPU, think databases and the like.
Hosting 20G hd, 1Tb bw! ssh $7.95
Agreeing with you... minor thing to further support your argument:
Xbox360 supports HD out of the box. Today. In stores.
[ducks]
ObLiterary: in this post-literate world, how many /. out there know the Swiftian basis for the terms "Big Endian" and "Little Endian"?
Swifts satire involved a controversy over which end of the egg you consumed it from.
Myself, I've always been and SHALL always be, a Little Endian!
Games often have far smaller cache requirements than many other applications, and as a result, it is preferable to go with a higher speed cache and higher CPU speed than a slower but larger cache/CPU.
:)
The Celeron in the 300A era are one of the best examples of this. They had half the cache of their Pentium III counterparts, BUT the P3 cache ran at half the CPU speed while the Celeron cache ran at full speed. The Celeron's performance was crap despite the faster cache for many applications (including server machines and most office applications) due to its smaller cache, but gamers discovered that for games, the situation was exactly the opposite - clock for clock the Celeron was significantly faster than the P3 due to the fact that most games in that era could fit almost all of their rendering pipeline within even the Celeron's small cache. Rare cache misses and twice the cache speed = much better performance. It also happened that that on-die cache allowed the Celerons to be overclocked like crazy, a significant added bonus.
The Xbox 360's CPU takes the whole idea much farther. While most desktop CPUs are designed to perform well over the widest range of situations (with some tradeoffs always being evident - note that Athlons eat P4s for lunch in many cases such as games, while Athlons do actually lose most of their advantages in performance per clock cycle when performing video compression and decompression because most video codecs don't have significant amounts of branching resulting in pipeline stalls from branch mispredictions.) The Xbox 360 CPU goes a step further by optimizing for one thing and one thing only - gaming. Instruction reordering which is critical in most desktop CPUs turns out to be not as necessary for gaming (specifically graphics rendering), and as a result the 360 drops instruction reordering capability completely in favor of having multiple cores at a low cost. (Instruction scheduling takes a LOT of die space in modern CPUs compared to the size of the rest of the CPU core.)
retrorocket.o not found, launch anyway?
Not a chance :) The COP interfaces contain bit vectors that are thousands of bits long, and only a handful of those bits are actually safe/useful to interact with for debugging the chip. Thats where the NDAs come in.
That is until you realize that the features that IBM and MS removed from the 360's CPU because they weren't needed for gaming cripple the CPU for most other applications.
retrorocket.o not found, launch anyway?
Not that I really care but I've read that the failure rate is 2% to 5% with the return rate at 1%.
It could be that the return rate is what Microsoft's official statement.
If there is a manufactured shortage of units, it could be that Joe sixpack is waiting for Wal*Mart to restock before returning their overheating Xbox for a newer one.
The news reports that they are out of the console but I haven't looked in the stores to verify.
if you steal from one source, that is plagiarism, if you steal from many, well, that's just research.
Thank you! For your edification:
its = possessive
it's = contraction of "it is"
Are there any reasons to get an Xbox 360 over PS3?
The XBox360 is (sort of) available now. The PS3 currently is nothing more than a haze of promises.
Are there any reasons to get an Xbox 360 over the original Xbox aside from graphical performance?
No, and probably not for PS3 over PS2, either. Don't expect a quantum leap in game design, just prettier graphics and more "stuff" on the screen at once.
PS3 will have better graphical performance, up to 2x.
According to Sony, whose advance claims for every previous console have turned out to be widely exaggerated.
High definition.
Also on the XBox360. HD is OK, but I'm actually more interested in the fact that widescreen will now be standard.
Blu-ray.
Every new Sony console seems to have some new, fancy drive design. And they always break down a lot. Be sure to get the extended warranty.
Up to 7 wireless controllers - those actually mean something.
If you can actually get 7 people around your TV. Maybe good for people with big-screen media rooms.
PS3 will come out with games that are just as good, perhaps better.
Perhaps. But the XBox360 games are coming out now. The PS3 won't be competing with XBox360 launch games, but with XBox360 2nd generation games. And the PS3 looks to be more of a programming challenge, so even if the hardware has the potential to match or surpass the XBox360, it may take years for that to happen.
5: PS3 will have better graphics in high definition. Maybe during it's lifetime, High Definition prices will drop sharply, just like LCDs have.
This has already happened. Walmart has rows of HD TVs in the $500-600 range. Many of them even have built-in tuners. If you don't demand a huge screen, HD is only a bit more expensive than SD, with a much better picture.
Yeah you can get it now, but you're basically just getting a graphical upgrade to your existing Xbox.
This is a bit silly. The XBox360 has a completely different processor and architecture than the XBox I, as well as a different graphics system. The PS3 is closer to the PS2 than the XBox360 is to the XBox I--that's why Microsoft has been unable to provide full backward-compatibility.
If you desperately need to buy something now, I'd buy a GameCube. It's dirt cheap, less than $100, and you can always pass it off to your kids, or younger siblings, cousins after you're done with it and decide what you want to buy next year when all 3 next-gen consoles are out.
Just-launched systems are for enthusiasts. The launch games typically barely scratch the surface of what the system is capable of. If you don't already have a game system, I'd recommend a PS2. Lots of games, fairly cheap used (but be sure to get an extended warranty). And promised backwards compatibility of PS3 means developers aren't going to be in a big hurry to switch to PS3 development. GameCube is more for people who appreciate Nintendo's unique game design strengths (I'm actually looking forward to Nintendo Revolution more than PS3).
Hate to burst alot of bubbles, BUT:
0 -2.ars/2
The Xenon CPU IS NOT the same as 3 G5's all on one chip! Read the arstechnica article here:
http://arstechnica.com/articles/paedia/cpu/xbox36
Basically it says: "The basic idea behind both Cell and Xenon is to make the execution core less complex by stripping out hardware that's intended to optimize instruction scheduling at runtime. Neither the Xenon nor the Cell have an instruction window, which means that these two processor designs largely forget about instruction-level parallelism. Instead, instructions pass through the processor in the order in which they're fetched, with the twist that two adjacent, non-dependent instructions are executed in parallel where possible."
This means that standard PPC code (OS X, etc) WILL NOT RUN on this. This is also the reason that IBM is selling these things at only $106 a pop to M$. Have you checked the prices for SINGLE CORE G5s for Apple? Their like $600-700 a piece! So, I am guessing that stripping these down makes them much easier and therefore faster and cheaper to mass produce, and therefore the price difference.
Anyway, there are reports that only one core is availble to intitial game developers, and one of the cores is strictly for M$ bullshit content protection TC such as the hypervisor, etc.
Not to mention from the article:
Microsoft and IBM engineers worked together during the definition phase of the project to specify a design to satisfy the constraints of a mass-produced consumer device
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). Cetainly not when the port to STI Cell architecture has been under dev for what, over a year? Damn, can't wait for PS3 release.
On one episode of "The Simpsons" (4F07), Ned Flanders asked Rev. Lovejoy a question of faith. That was his reply.
Ned: Rev. Lovejoy, with all that's happened to us today, I kinda
feel like Job.
Lovejoy: Well, aren't you being a tad melodramatic, uh, Ned? Also, I
believe Job was right-handed.
Ned: But Reverend, I need to know, is God punishing me?
Lovejoy: Shooh, short answer: "Yes" with an "If," long answer: "No" --
with a "But." Uh, if you need additional solace, by the way,
I've got a copy of something or other by Art Linkletter in my
office.
God save our Queen, and Heaven bless The Maple Leaf Forever!
This is a fully PowerPC compliant chip. Make no mistake. It WILL run standard PowerPC code, as will Cell BE. From where did you get that the singe core G5 costs 5-600 dollars? An iMac G5 (singe core PowerPC 970FX costs $1300 and that's a complete computer with a GPU, harddrive, DVD-burner, webcam, 512 MB RAM, an 17" TFT, package, shipping, advetising and about 30% margin.
The cost of a processor is directly related to the die size and since the size of the Xenon is larger than the dual core G5 (about 130 million transisotrs compared to 165 million in the Xenon) there's a good chance that Xenon is actually more expensive than the PowerPC 970MP to manufacture.
Linux will run just fine on an Xbox 360 if one would fins a way around the DRM stuff. OSX too if Apple would want to. Same goes with the PS3. Hell.. Sony's boss even said so!
- Henrik
- when the Shadows descend -
A 5% failure rate for an "appliance" type consumer electronics device is generally considered acceptable in the industry.
The kind of "stress test" you propose would be unprecidented in the history of consumer electronics. It would also be the easiest way to make sure your production line is as inefficient as possible (think about the scale of what it is you are proposing). Finally, it still won't catch problems that are the result of damage occuring during transit.
In a production line you depend on your suppliers giving you parts that work to your specifications, and you make sure that when you put them all together the unit passes a set of diagnostics. Any problem that gets past that process is handled by the product warranty.
* I don't make much of a distinction between memory and cache because in this case it's pretty much the same anyway. Also note, that while the VRAM is one problem, the small caches of the vector units are also a nightmare to program. But in this case it's mostly a question of how much effort you want to put into a game to squeeze out a few more polygons/effects. IIRC Squinter Cell had a whole development team, almost as big as all of the others combined, dedicated to adapt it for PS2. The results were quite impressive.
Don't think of it as a flame---it's more like an argument that does 3d6 fire damage