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JTAG 'Hacking' the Original Xbox in 2023
I remember watching the XBOX talk. The one thing that really stood out was how the Flash ROM happened to contain a previous version of the hidden ROM sitting right there. While it didn't exactly match the release version, it still provided a whole lot of information on how the boot sequence worked.
The CPU choice was changed last minute from AMD to Intel. Andy Grove and Bill Gates had a last minute phone call. The demo on the stage was still using AMD.
How last minute was this? This wasn't exactly socket 7 Days anymore, so I guess you still needed to change quite a bit of "stuff" to make this work, for example the Nvidia chip as it was the south bridge iirc.

Did any of these amd prototypes ever pop up on ebay? Would be another cool project 20 years later to try and get them to run...

The engineering teams were probably running both programs in parallel. I've had this happen to me several times. Sometimes, project B is just leverage [1] so that a better deal can be negotiated, so you half-ass project B, and that's fine and just business. But sometimes it's not, and that situation sucks.

[1] Factory resources are scarce, so it's obvious to the engineering team how serious management is about things. Word spreads.

"Seamus Blackley apologized on Twitter to the AMD engineers who worked with Microsoft to create the prototype Xbox consoles that the company used in the lead-up to the OG Xbox's release in November 2001. To AMD CEO Lisa Su, Blackley said, "I beg mercy."

"I was standing there on the stage for the announcement, with [Bill Gates], and there they were right there, front row, looking so sad," he said of AMD engineers in the room. "I'll never forget it. They had helped so much with the prototypes. Prototypes that were literally running the launch announcement demos ON AMD HARDWARE."

"I felt like such an ass," Blackley said."

https://www.gamespot.com/articles/20-years-later-xbox-creato...

Wow. I mean there's a colloquial "last minute" but that sounds like a literal, last minute.

> Wow. I mean there's a colloquial "last minute" but that sounds like a literal, last minute.

Man, indeed. Must've really sucked if that guy still thought about it 20 years later. But well, at least amd is in those consoles today. :)

Still wonder where those AMD prototypes are today. Seems there's a non-zero chance to get them working with release titles.

One example of a "Project B" happening was between Nintendo and Citizen during the time of the Game Boy. Citizen had a color LCD screen available, and there was progress on designing a handheld game console to use that screen. But it turned out to be a Project B to negotiate with Sharp and use their black and white LCD instead. Then Citizen proceeded to work with Sega instead with the Game Gear.

Source: LowSpecGamer on YouTube

Given that this was circa 2000, could have had provisions for 2 more prototypes for Transmeta and VIA. I doubt they would have gotten far or even start given that they likely wouldn't have very competitive options, but it's fun to think about.
If I remember right the original xbox cpu (intel) was a derivative of the 733 MHz Pentium 3, which came in a 'socket 370' package for assembly on regular x86 motherboards. It's several generations beyond the socket 7. The xbox cpu to me looks similar to the soldered onboard pentium 3 mobile interface used in laptop manufacturing at the same time, no socket, just BGA soldered onto the board.

google "pentium 3 coppermine" for some more info on the series of CPUs...

I thought nvidia did the northbridge as well since it had the igp? Given they were able to use the tech for nForce I'm guessing they did both at about the same time
  • pjc50
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> The most critical part of the install was nailing the alignment and reflow of not just one, but BOTH ball-grid-arrays for welding over a single rework profile.

Oof. For someone who describes themselves as a software engineer, this is an extremely nice piece of work.

I wrote this post. March 1st I'll be giving a related conference talk at RE//verse (https://re-verse.io/) about my journey from software reversing into the realm of ludicrous hardware research while re-visiting the Original Xbox. It will be recorded and available online at some point after the conference.
Phenomenal piece of engineering, especially the soldering and figuring out why it wouldn't boot with the debugger attached.
Projects like this has always inspired me to learn new things that just so happen to help me grow professionally.
This has been reposted a few times with more commments:

https://hn.algolia.com/?query=JTAG%20%27Hacking%27%20the%20O...

> Within three months of launch, this secret bootrom was infamously dumped by Andrew “bunnie” Huang blowing the console wide open to further research.

TIL. I never knew about that one - I always thought him being famous came of his various work surrounding the "gongkai" ecosystem.

  • pjc50
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He has a whole book on the subject! Great hardware hacker.
https://nostarch.com/xboxfree
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Designing a custom interposer is crazy
CPU interposers in the OG Xbox community isn't uncommon. You can drop in a retail PII with double the clock speed but it requires an interposer.
Funny timing, I just finished (re) readong "Hacking The Xbox" two days ago.
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