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Easy convert of BASIC rev A to rev C


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Don't know if the seller above has more on Ebay, but he was selling genuine Atari BASIC REV C ROMs for $4.31 plus $7.50 shipping from England. If you buy more than one, he only adds 1 GBP per additional ROM for postage. Most of us have the rev A ROM cartridge. You know you have rev A because it has the original brown label. Rev B was for the internal 600XL and 800XL, but it still had flaws. Rev C shipped in the XE and some late XLs, plus in cartridge form. The ones with rev C have the silver label. Most rev A cartridges have two 24 pin 4KB ROMs that are in sockets. Not all are in sockets (some are soldered in), so you'll have to remove the screw on the back and look. If you have one with sockets, you have an easy path to upgrade to rev C. Atari in their infinite wisdom was very smart in their design layouts, even in 1979. Those rev A cartridges with two 4KB ROMs can accept one 8KB ROM in the right socket. You simply remove the two 4KB ROMs and insert the right socket with an 8KB rev C BASIC which is also 24 pin. Nothing else to do, but put the cover back on. Your 400, 800 or 1200XL will recognize the 8KB ROM and viola, you have rev C BASIC in our BASIC cartridge. No cutting of traces, adding resistors or any mods at all. A pleasant surprise.


Rev A had errors that caused lock ups.

Rev B fixed the A error, but introduced another that came up more often.

Rev C fixed the issue and is the most sound version of Atari BASIC.


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Your list about the bugs is right, but not so clear.


Indeed in rev. B there are new introduced bug(s) but one of them is also a random lockup of the atari.


I had an 800XL back then, with that Rev. B basic, and that is where my almost neurotic behavior of making backups (still today) comes from. I have typed my fingers blue on type-in game listings and seriously, without ANY warning my atari simply froze after pressing the return key sometimes. So every 10 minutes or so I saved my listing to a tape.


Later there was this small ML routine that would fix the internal BASIC rev. B into C, but I found it more trouble to load that everytime, than to keep with my neurotic backup-saving-behavior lol.


Well it was quite educational to learn how important backups are ;)

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Just download and burn a Rev. C BASIC ROM. If you don't have access to a programmer, I'm sure many people would burn you a ROM. It's no big deal.


Edit: Or simply buy one from Best or B&C.


I don't know if Brad at Best still has any, and even if he does, he has a pretty high minimum purchase requirement. So unless you are planning a large order from him, the Ebay deal with shipping isn't all that bad. Don't know if Bruce has any, or at what price, but it might be interesting to check and see for a comparison. I personally like the idea of having a genuine Basic C ROM instead of an EPROM for upgrading my XL's.


- Michael

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What types of (E)EPROMs can be used?

There are some EPROMs/flash ROMS that are compatible with the 2364 ROM.



A 2764(or larger) EPROM can also be used, but an adapter or jumpers wires are required.



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