lindoran

Thanks for the clarification, I'll keep looking for a matching ROM... Also as an update, I did manage to tweek alteras settings to get it to load the ROM onto the xl profile.

So did some more digging. I tried dumping the rom loading it with the basic cartridge installed, got the same results. So then I tried something completely different. When you boot the machine into basic with the XL rom installed and PEEK 65527, you get 2 When you boot the machine into basic while in the 2nd rom (holding down option while booting) and you PEEK 65527, you get 255! You get the same results to peek with the basic cart installed. referencing this web page: https://atariwiki.org/wiki/Wiki.jsp?page=OS Versions does that mean I have the missing First 800 OS for NTSC, or at least an XL fix based off that ROM?

here's the output from the computer when it is in XL mode, it does come up as an XL CRC-32 .... I gotta go to work this is definitely weird basic.rom os.rom

Ok so ... dumped the rom, with the program you sugested. I learned 2 things 1... the rom that i got out was byte for byte the same using the little java program you sugested. 2... the basic rom that dumped was correct (from this we can deduce the program properly dumps basic roms) I am out of time but I left my atari dumping in XL mode to see if the rom output is the same with the XL os loaded up, or if i get a proper XL OS using the same method.. here is my output: basic.rom os.rom

Could be my basic program. I may have messed up the address space, I was following someone else's code. When the ROM boots up it does not boot basic by default. You have to hold down option to get basic to load. But if this is not happening it's probably a bad dump. I'll try the program as soon as I get home from work

Here's the os rom dump and a copy of the program i used to obtain it. dump.bas osimg.rom

I'll take a look at the basic program to dump the ROM when I get home later 😁. Thanks for the help! I already re-socketed the mod and verified it's working, right before I left.

Thanks for the answer on that .. I'm still learning, tbh throwing the switch and causing a crash while it was on is how i decided to pull the chip. Glad its not as bad as I thought. just wonder whats on it.

I had a 800XL left to me from my wife's grandfather, it was his dads computer actually. It has a odd OS piggy back mod, which i removed this morning, I don't have a eprom programmer so I can't read off the chip what specifically it is. The reason i removed it is it was wired to the chip select using a piece of silver satin phone patch and a simple SPDT (I think) switch with no way to protect against switching while the machine is hot. Another odd thing is this computer hasn't been used since perhaps the very early 90's. I'm told the original owner was fairly astute with electronics, so it would be a period accurate upgrade. The computer didn't come with a modem so its likely something he either read about in a magazine or sent away for. The eprom window is actually spray painted over, there are numbers on the bottom of the ROM chip which are "Silicon Signature MP47005UB", with what i think is a date code of 8349. The Google box reveals nothing. I'm thinking the fact that the chip was sprayed over means somebody didn't want the chip to be re-used, or re-blanked. Anyone have any idea what I'm dealing with here?