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Xbox 360 Architecture

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Re: Xbox 360 Architecture

#51

Post by anyfoo »

kmeisthax wrote: post #45
wmf wrote: post #41

Earlier quoted context omitted.

You're comparing the 2012 Wii U against 2005/2006 360/PS3. The PPE was indeed terrible but it's not clear that IBM had anything better available at that time.

The Wii U also needed to be backwards-compatible with the Wii, which used the bespoke paired singles and locked cache line features of the GameCube's PPC 750 derivative. This almost certainly locked them out of newer PowerPC designs without more engineering work than Nintendo would be willing to put into its systems. For context, Nintendo has always been weirdly quirky and low-buck when it comes to core silicon engin…

Super interesting comment.

> which used the bespoke paired singles and locked cache line features of the GameCube's PPC 750 derivative

Where can I find some information on that specifically?

Re: Xbox 360 Architecture

#52

Post by djmips »

pinewurst wrote: post #47
kmeisthax wrote: post #45

Earlier quoted context omitted.

The Wii U also needed to be backwards-compatible with the Wii, which used the bespoke paired singles and locked cache line features of the GameCube's PPC 750 derivative. This almost certainly locked them out of newer PowerPC designs without more engineering work than Nintendo would be willing to put into its systems. For context, Nintendo has always been weirdly quirky and low-buck when it comes to core silicon engin…

Ricoh not Nintendo ripped off MOS IP.

Nintendo shipped it and I'm sure they knew.

Re: Xbox 360 Architecture

#53

Post by Arrath »

anyfoo wrote: post #50
Arrath wrote: post #46

I finally got through this, coming in and out throughout the work day. I owned 3 360's over the lifespan of the console (a launch version, a replacement after it red ringed a few years later, and then a slim), and I never even brushed up against the cracking or homebrew scene. Very interesting stuff! I am curious though, other that one brief mention, why didn't you touch on the early hardware reliability issues at al…

> I am curious though, other that one brief mention, why didn't you touch on the early hardware reliability issues at all? I guess because they likely didn't have anything to do with the architecture? Or were there really reliability issues that were a result of the architecture, instead of physical/electrical hardware issues?

Fair. I was thinking in terms of the physical architecture of the boards, cooling solutions, and entire consoles rather than the pure architecture of the cpu, gpu, etc.

Re: Xbox 360 Architecture

#54

Post by wmf »

anyfoo wrote: post #51
kmeisthax wrote: post #45

Earlier quoted context omitted.

The Wii U also needed to be backwards-compatible with the Wii, which used the bespoke paired singles and locked cache line features of the GameCube's PPC 750 derivative. This almost certainly locked them out of newer PowerPC designs without more engineering work than Nintendo would be willing to put into its systems. For context, Nintendo has always been weirdly quirky and low-buck when it comes to core silicon engin…

Super interesting comment. > which used the bespoke paired singles and locked cache line features of the GameCube's PPC 750 derivative Where can I find some information on that specifically?

http://datasheets.chipdb.org/IBM/PowerPC/Gekko/gekko_user_ma...

Re: Xbox 360 Architecture

#55

Post by randomifcpfan »

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…

Your heart is clearly invested in this project. But compare the wordiness of your doc to a primary source like https://old.hotchips.org/wp-content/uploads/hc_archives/hc17...

You should ask yourself “why am I writing this document“, and then check to see if the document is achieving your goals. I am guessing your goal is “I want to serve as the definitive publicly available textbook for the Xbox 360.“. If that’s your goal, I would split the doc into chapters by topic, and then edit the heck out of each chapter. Look at a model textbook like Computer Architecture, a Quantitative Approach, and see if you can imitate their style.

I think a good technical editor could help you edit this down to about 25% of the words, and still cover the same information.

The job is too big for drive-by code review style comments. You’re going to have to put in the work yourself if you want to improve this.

Re: Xbox 360 Architecture

#56

Post by astrange »

bee_rider wrote: post #37
bombcar wrote: post #21

Earlier quoted context omitted.

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.

This is speculation, but: optimizing compilers are pretty good, right? On x86 at least. Perhaps they do a good job on popular platforms like x86, because we can encode decades of experience, but not so great on brand new ones.

Optimizing compilers aren't that great on x86. Sure, they're good enough to make something 60fps that wasn't before, but they don't really have much specific x86 knowledge.

Re: Xbox 360 Architecture

#57

Post by anyfoo »

I love this series. A minor point about the layout only: I know you are very fond of those tabbed boxes (as I've seen them in every such article of yours that I read over the years), and I bet they make a lot of sense when reading on a mobile device, but on my desktop browser with plenty of screen space I often wish they weren't there. I.e., I wish everything was always visible and maximally require (normal vertical) scrolling.

This is especially true for things you intend to compare. For example, I was awkwardly flipping between the "Xenon" and "Cell" tabs a lot, to compare the two block diagrams.

Re: Xbox 360 Architecture

#58

Post by wanderingmoose »

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.

Here's a good explanation of some of the issues w/ common programming patterns at the time colliding with the 360 design. This was a huge problem with the initial ports of older game engines to the 360 that required a lot of rewrites to achieve ok performance.

https://www.gamasutra.com/view/feature/3687/sponsored_featur...

Re: Xbox 360 Architecture

#60

Post by bmalicoat »

Great resource, nice work putting it all together. I was on the software side of 360 (mostly C++ and Lua), so I didn't get too deep in the hardware. Most of my time was spent modifying and building on the XAM, glad to see it mentioned briefly in there!

The old screenshots of the dash bring back lots of memories. The releases were all named after European cities at the time; Berlin, Geneva, Stockholm, Madrid, etc.

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