I bought an 800XL on ebay and when I powered it up...

[DavidMil]

I bought an Atari 800XL from ebay. When it arrived in the original box I was surprised at how good it looked. There was just one minor problem;

there was nothing in the box but the computer. Not a problem as I've got several power supplies, etc. Anyway, when I powered it up I saw the

good old blue screen, but no cursor and no memo pad, and then the self test screen comes up. Ok, run all self tests. It ran through all the tests

with out any problems, except the RAM test only counted up to 40K, then it would go to the next test. So I ran the memory test a couple of more

times and each time it would stop at 40 K (all green). So I found my super salt cartridge and ran it and it didn't find any problems. With a sigh I picked

up my Philips screwdriver and opened the case. Everything looked good and clean except there was no Basic Chip in the machine, just an empty

socket.

My question is, has anyone every run the self test without a Basic chip in the machine, and why didn't it give me some king of error? And why didn't

super salt show a problem with the RAM? I'm going to throw an old 'A' series Basic chip in the machine and see if it finds the missing 8K. By the way,

Defender and Asteroids cartridge games came up fine. I'll let you know what happens after I but the Basic chip in.

 

DavidMil

[+DrVenkman]

Huh. That's odd. Any indication of other mods inside the machine?

[+Nezgar]

I was recently testing replacing the BASIC chip in an 800XL with an adapter for my own 27C64 eprom with BASIC rev C, or larger for switching between say RevC, altirra basic, and Asm/ed or 8K games.

 

I found that with no chip present, the system will boot up just as you described, going straight to self test just like if OPTION was pressed to disable BASIC and no bootable disk was present.

 

I didn't let a memory test run long enough to notice the 8K missing, but that would make sense as the MMU would still be allocating that block of memory to the missing ROM, unless you hold down Option.

 

Inserting a cart would just override BASIC anyway too, so should be no problem.

[+Nezgar]

Self test only checks integrity of the OS ROM, not BASIC I guess.

[Rybags]

Self-Test doesn't do anything with Basic. The ROM not being present will still mean RAM not appearing at the relevant addresses.

[oracle_jedi]

I removed the BASIC chip from an 800XL and it did exactly what yours is doing - booted up to Self Test and only tested 40K.

 

The 8K for BASIC is still masked out, even though the chip isn't present.

 

Hold down OPTION on start up and try the test again, you should get 48 blocks.

[R.Cade]

Yep, this is normal behavior. I had one with a bad BASIC chip that did this. Also, using a BASIC cart from an old 800 does not work right- the machine still acts funny trying to run BASIC programs, even though it appears at first to work...

[DavidMil]

I removed the BASIC chip from an 800XL and it did exactly what yours is doing - booted up to Self Test and only tested 40K.

 

The 8K for BASIC is still masked out, even though the chip isn't present.

 

Hold down OPTION on start up and try the test again, you should get 48 blocks.

 

I held down the option key at power up and sure enough it tested 48k just fine. I couldn't find an 'A' series Basic chip (probably cause I pitched it)

so I used a 'B' series chip and the computer booted up just fine. So as oracle_jedi and R.Cade said, "this is just normal procedure." My thanks to all for their input!

 

DavidMil

Edited July 5, 2018 by DavidMil

[BillC]

 

I held down the option key at power up and sure enough it tested 48k just fine. I couldn't find an 'A' series Basic chip (probably cause I pitched it)

so I used a 'B' series chip and the computer booted up just fine. So as oracle_jedi and R.Cade said, "this is just normal procedure." My thanks to all for their input!

 

DavidMil

There was no 8k Revision A BASIC chip. Revision A is the brown label BASIC cartridge which contains 2-4k ROM chips, and was for use with the 400/800/1200XL.

[Mclaneinc]

Glad you got it sorted David, really odd to get a machine minus a chip without being told, that's Ebay for you..

 

Good it was a pretty simple fix and the B series BASIC should be 99.999999999999999999999999999999999999999999% fine...

 

(bet he boots up the one program that needs series A next )

[_The Doctor__]

rev c... that's what you wanna drop in there!

[+Nezgar]

Rev B is probably fine for generally running programs... the problems are mostly encountered when actually trying to program with it....

[DavidMil]

There was no 8k Revision A BASIC chip. Revision A is the brown label BASIC cartridge which contains 2-4k ROM chips, and was for use with the 400/800/1200XL.

 

A clear case of typing without thinking! Somewhere in the cobwebs I remember that A Basic was a two chip package. Since I have a B chip I'll just

leave that in there. It's for my youngest son (42 years old), and all he's going to do is play the games he grew up playing. Just like most of us do...

 

DavidMil

[Kyle22]

A 68766 is a direct drop-in if you can find one to burn ver.C on.

[BillC]

A 68766 is a direct drop-in if you can find one to burn ver.C on.

Or get an adapter which allows the use of a 2764 compatible chip, which are less expensive and much easier to find.

 

http://store.go4retro.com/2364-adapter/

 

 

Some models of the 600XL have 2 jumpers which already allow the use 2764 EPROMs for internal BASIC, the socket must be converted to 28 pin also.

Edited July 9, 2018 by BillC

[DavidMil]

Or get an adapter which allows the use of a 2764 compatible chip, which are less expensive and much easier to find.

 

http://store.go4retro.com/2364-adapter/

 

 

Some models of the 600XL have 2 jumpers which already allow the use 2764 EPROMs for internal BASIC, the socket must be converted to 28 pin also.

 

For $5.00 you can't go wrong. I just ordered one!

 

Thanks,

David

[+Nezgar]

For $5.00 you can't go wrong. I just ordered one!

 

Yeah these things are cool. This is the adapter I was playing with in a recent thread to replace the stock OS ROM with a 27C64 programmed with Atari BASIC Rev C, and then later trying bank selecting 4 separate things on a 27C256 like BASIC Rev C, Altirra BASIC, ASM/ED and an 8KB game. A single SPDT switch will select 3 of the 4 slots of a 27C256. You could switch between 8 things with a 27C512.

 

I got some of their bare PCB's as they were cheaper to ship to Canada, and found you don't need the 3 resistors with just an 8KB 27C64. I installed pin headers on the 4 bank select through-holes for easy install/removal.. I tested with a 4-wire jumper I hacked together for temporary testing. Maybe I can use the right angle headers, but the main problem I found is it doesn't fit next to the AtariMax 32-in-1 OS board... So unless maybe if I solder it directly to the 800XL motherboard in place of the original socket, I'll save this for another machine with a different OS ROM setup.