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Hi again,


this must be awfully often discussed but yet I don't seem to find anything useful -- I'm looking for the XEGS game ROM, i.e. the one I can put into Atari800 emulator. I want to compare real hardware with emulated, just to be sure everything is all right. And Atari800 refuses to boot in XEGS mode unless I supply the game rom.

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Missile Command can be downloaded as a Rom in it's own right, as well as executable for >= 48K Ram machines.


In most cases in emulation we just use an XL Rom of 16K and don't worry about emulating XEGS closely.

The Missile Command in XEGS is 6K just like the original and the same except for 2 bytes.


The original MC did the wrong thing in that it used direct reference to the OS keymap which isn't guaranteed to be fixed in place in the OS Rom. That was OK with 400/800 but became incompatible to a point with the XL as it's keymap is in a different place.

Instead of bothering to fix it properly, all they did with the XEGS version even though there's 2K of the Rom with zeros, is they changed the reference to the keymap so it'd work again. For a built in game though it doesn't matter since you know that the OS it will work with should be present.


Anyway, I have NFI if this works or not but I've got a 32K Rom file which should match what an XEGS has:



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If you just want to do basic testing, just grab any 8K cartridge ROM and stuff it in Atari800's custom XEGS game slot to get things going. The XEGS doesn't really care what its game ROM is, as it just starts it like a cartridge. If you really want the fully authentic in-box Missile Command experience, though you need to get the actual correct ROM instead of the 400/800 one as Rybags notes; the correct 8K game ROM has a CRC32 of BDCA01FB.


The OS ROM also needs to be version 4 for the XEGS to completely act as documented. The common version 2 OS, usually named ATARIXL.ROM, will mostly work but some things won't be quite right -- it won't launch the game ROM, SELECT won't toggle the keyboard attached/detached behavior, and you won't be able to start a cassette tape load with the console buttons.

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Thanks guys. I had a 32K ROM dump as well but I didn't realise the cart is 8K, not 16K. So after splitting the file to four 8K blocks Atari800 detected BASIC and Missile Command and after joining the remaining two files together I got a shiny REV04 OS as well. :)


So, Atari800 is not complaining anymore and I can enjoy XEGS in my PC. Or can I? For some strange reason, the ROM bars in Self Test are red. WTF? And I wanted to use emulator to check whether things are all right on real hardware. :) All ROM dumps are 100% correct (Atari800 automatically recognises them), I tried Altirra as well and guess what? Green!


Has anyone ever seen something like this? Altirra may be more recent but this looks very suspicious, it's basic functionality after all.

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