Xbox 360 Architecture • Hacker News Board

Re: Xbox 360 Architecture

#11

Post by Hellion » Fri, Jun 10, 2022, 3:12 PM UTC

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…

> I don't know how else I could improve this, but I'm always open to suggestions.

I issued a minor correction on the GameCube article and you were extremely quick to correct it.

Op: if you’ve found something, please post it. Everyone benefits :)

Re: Xbox 360 Architecture

#12

Post by bombcar » Fri, Jun 10, 2022, 3:16 PM UTC

It's amazing to think that we had already hit peak gigahertz, and multi-core was just starting to become a major "thing" at the time.

Even with the advances in the M* chips from Apple, it seems the "chip wars" are basically over, at least on the design choice side of things.

Re: Xbox 360 Architecture

#13

Post by georgia_peach » Fri, Jun 10, 2022, 3:25 PM UTC

Great write-up. Enjoyed it up to the RAM encryption part. From there on, I was too filled with Stallman-rage to appreciate the technicals.

Re: Xbox 360 Architecture

#14

Post by bluedino » Fri, Jun 10, 2022, 3:30 PM UTC

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?

Re: Xbox 360 Architecture

#15

Post by Nouser76 » Fri, Jun 10, 2022, 3:39 PM UTC

Super exciting read! I was interested in the Xbox 360 modding scene and re-reading this brought back a ton of memories from reading about all this stuff the first time!

Thanks for compiling this, the quality is excellent and the content is approachable.

Re: Xbox 360 Architecture

#16

Post by Veliladon » Fri, Jun 10, 2022, 3:45 PM UTC

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?

It wasn't a POWER thing since POWER has been superscalar since the 604 back in '94. This was because when you're designing for a console and paying by the wafer instead of shopping around for a pre-finished unit one needs to consider die area more strictly. Something had to give in the design and given MS controlled the design of the whole stack they thought they could do parallelism at the thread level in the OS scheduler rather than having to devote massive amounts of die area to it.

Re: Xbox 360 Architecture

#17

Post by corysama » Fri, Jun 10, 2022, 3:50 PM UTC

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?

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 of the very long, very static, very linear pipeline of the CPU. In practice, that only makes sense for very long stretches of instructions with no branches and no cache misses —which is completely the opposite of every piece of gameplay code ever written. The CPUs were great at large scale linear algebra. Not great at much else.

Re: Xbox 360 Architecture

#18

Post by Jerrrry » Fri, Jun 10, 2022, 3:55 PM UTC

This is beautiful.

I wish I could remember enough to contribute, especially to the DEV/XBL online chapters.

If I ever recover my old /modding/ folder, I will reach out [OP].

I was pseudo-privy to a lot of non-public stuff that I think the public could benefit now from, with a decade passing, I think it would be be appropriate to share.

Re: Xbox 360 Architecture

#19

Post by krylon » Fri, Jun 10, 2022, 3:56 PM UTC

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!).

Re: Xbox 360 Architecture

#20

Post by HyprMusic » Fri, Jun 10, 2022, 3:56 PM UTC

Wow what a journey the homebrew section of that article was. As someone who grew up heavily involved in the evolving Xbox homebrew scene, I dipped out of consoles before the 360 was truly cracked. I remember the sadness in realising the DVD drive exploit had effectively killed off any interest in trying to run homebrew, but I'm thoroughly glad to learn that the community not only persisted, but became incredibly inventive.