Speaking of GBA mods, the bloke at work pointed me at:

http://www.ngine.de/site/hamdoc/korth_gbatek.htmlhttp://www.ngine.de/site/hamdoc/korth_gbatek.html

- looks informative. (It seems as though theres a hard-wired interrupt handler which faffs for a bit before going to a user routine, so its quite a bit less responsive than an ARM is capable of being, but it looks as though its capable enough.)

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Fluppet