Original Xbox Hacks: The A20 CPU Gate (2021)

Comments (4)

mjg59 · 22m ago

A20 bugs were still with us until at least 2009, when I tripped over one: https://mjg59.livejournal.com/118098.html . I love the visualisations in this post, it makes it much clearer what's actually going on.

LongjumpingCat · 11m ago

This really hit home. Those old Xbox ads are such a time capsule, a mix of “we’re edgy” and “we want to be cool” but not taking themselves too seriously.

pwdisswordfishz · 1h ago

I was confused as to why Xbox would ever enable a feature intended for backwards compatibility with systems it does not need to be compatible with. Especially at boot time. Turns out it did not; this apparently required a hardware modification to pull off.

https://xboxdevwiki.net/Exploits#A20M.23_hack

userbinator · 1h ago

For those wondering what software depended on A20 wraparound, there is this interesting series of articles:

https://www.os2museum.com/wp/who-needs-the-address-wraparoun...

https://www.os2museum.com/wp/the-a20-gate-it-wasnt-wordstar/

https://www.os2museum.com/wp/exepack-and-the-a20-gate/

https://www.os2museum.com/wp/the-a20-gate-fallout/

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Original Xbox Hacks: The A20 CPU Gate (2021)

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