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Xbox 360 Architecture

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Re: Xbox 360 Architecture

#21

Post by bombcar »

corysama wrote: post #17
bluedino wrote: post #14

Earlier quoted context omitted.

Is that a POWER thing or what was the main cause?

On top of being power architecture, both the 360 and the PS3 chose to push the 4 GHz clock limit before everyone else. To do this they sacrificed lots of speculative and out of order execution features of the CPU. The thinking of the hardware engineers was that the software is compiled for a fixed architecture doing a fixed job so the compiler should be able to statically order the instructions to make the best use o…

The "compiler will solve everything" theory seemed to last quite a long time, I first heard it with the Itanium and again with these pipelined CPUs.

Narrator: It didn't solve anything.

Re: Xbox 360 Architecture

#22

Post by l8nite »

meheleventyone wrote: post #10

I used to have a G5 Mac living a second life as a doorstep with a “property of Microsoft” sticker on it because they were used as early alpha devkits for the 360. Given away at the company I worked for a year or two after the 360 shipped. Rumour has it they were even delivered at the dead of night so no one would see the MS branding on Apple hardware.

Hah, I had a mac360! I used it when working on some early Kinect voice-recognition stuff.

Re: Xbox 360 Architecture

#23

Post by torginus »

I wonder how true this rumor is, but I remember reading that around the time the F35's computer system was designed, Lockheed Martin shopped around for CPUs from different vendors. PowerPC was a very popular architecture used in military hardware, so LM contracted IBM to design a CPU for them.

In Aerospace applications, it's very popular to have triple-redundant system, that's why IBM designed an unusual 3-core PowerPC CPU. Later, when Microsoft came into the picture, they used the design, with essentially minimal modifications.

I haven't followed the F-35s development that closely, so I have no idea what they ended up using, but it's an interesting rumor nontheless.

Re: Xbox 360 Architecture

#24

Post by snerbles »

krylon wrote: post #19

Fascinating read. It's funny to me that IBM - a company not known to promote fun and games - ended up providing the processors that powered the PS3, XBox360, and I think the GameCube and Wii, too. Thank you very much for the deep dive, I imagine the research must have been exhausting (but also rewarding, I hope!).

IBM was the real winner of the seventh generation console war.

Though by not as much of a dramatic margin (Nintendo stayed with IBM for the Wii U and Nvidia for the Switch), one could say AMD won the eighth- and ninth-gen console wars in a similar fashion.

Re: Xbox 360 Architecture

#25

Post by javagram »

torginus wrote: post #23

I wonder how true this rumor is, but I remember reading that around the time the F35's computer system was designed, Lockheed Martin shopped around for CPUs from different vendors. PowerPC was a very popular architecture used in military hardware, so LM contracted IBM to design a CPU for them. In Aerospace applications, it's very popular to have triple-redundant system, that's why IBM designed an unusual 3-core Power…

FWIW, the Xbox 360 chip was based on the processor developed for the PS3. No mention of F-35 here. “These cores are slightly modified versions of the PPE in the Cell processor used on the PlayStation 3” https://en.m.wikipedia.org/wiki/Xenon_(processor)

Re: Xbox 360 Architecture

#26

Post by reachableceo »

flipacholas wrote: post #9
randomifcpfan wrote: post #6

A labor of love that would benefit from reorganization and editing. It could also use a round of fact checking. Some of the info appears to be based on third-hand speculation.

Hi, this took me 6 months to write, I've also tried as hard as possible to cross check all my references, and include them in the article in a way the reader can find the citations just like in academic writings. Statements denoting speculation are started with words like 'presumably' or 'it is assumed that'. I've also took an extra month to send the draft to many experts (part of whom are still active in the Xbox 36…

Ignore these general swipe remarks. They are done by people who don’t have the passion and ability to ship something like you do!

The overwhelming tone of the comments here is positive. You took a complex subject , researched it deeply , open sourced it . That’s so rare.

Ignore the haters, always.

Re: Xbox 360 Architecture

#27

Post by zenron »

bluedino wrote: post #14
john567 wrote: post #3

This thing branched horribly. You had to use instructions to selectively write to distinct memory locations to avoid typical branching because misprediction was expensive. This was Frostbite/Battlefield 3 era. Good Times.

Is that a POWER thing or what was the main cause?

As said in other comments, not a power thing. Example, the Nintendo Wii U chose to use 3 1.2ghz (iirc) Out of Order execution cpu's that were more like a PC than the cores in the Xbox 360 even though sounding similar in instruction set and composition.

This lead the Wii U to be able to do things like Run Mass Effect 3 and Deus Ex better (arguably) than the PS3 and 360 most of the time. The Wii U was probably the better hardware platform in hindsight but it came too late and the development tools were not as robust so ports just kinda afterthoughts.

Re: Xbox 360 Architecture

#29

Post by landr0id »

Super minor nitpick but ROP wasn’t used for the King Kong/SMC exploit. I would consider it a ROP exploit if multiple return-oriented gadgets were chained together to form a full exploit chain, but what happened here is the syscall handler was invoked with a malformed index causing a single jump to user-mode code with kernel-mode privileges. It’s not too dissimilar to calling an arbitrary function pointer.

Otherwise this is a great comprehensive rundown!

I was just recently talking to a coworker too about how I think the Xbox 360 was the first consumer device to have the following types of attacks done to it:

1. Hypervisor attack to then reboot the console into a newer system OS version to retain the vulnerable hypervisor but be able to play new games and get online. This required soldering a separate flash chip to hold the newer system files.

2. Fault injection (reset glitch hack) to attack the system's bootloader

As a teenager who learned programming/hacking by messing with the Xbox 360, I'm thankful that Nintendo is still keeping the dream alive for our next generation of hackers.

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