800 memory upgrade

[joejones]

I have read several comments about 256k and 288k memory upgrades for the atari 800. I would very much like to build one but I haven't been able to find any diagrams or pictures. Can anyone help me out here.

[carmel_andrews]

the person you need to ask for is were rat(or was it wereat)...he seems to be specialist in this area

 

just my 2p's worth

[sup8pdct]

I have read several comments about 256k and 288k memory upgrades for the atari 800. I would very much like to build one but I haven't been able to find any diagrams or pictures. Can anyone help me out here.

 

If I dig around, I just may find a add on board for the middle ram board for the 800. It requires an original board, several cut tracks and soldering.

8 256X1 ram chips.

It will help greatly if the covers are removed from all the ram modules and the os rom module.

The late 800's didn't have any covers and the boards had a single plastic spacer to hold them still.

 

James

[1050]

The series of .pic pictures on this atr are the only pictures I know of.

http://ape.dyndns.org:8083/UMICH/MODS/ADDMEMA.ATR

 

But that particular mod has trace cuts and mods shown for to use D700 address to bank the ramdisk instead of the more standard CFFF address so watch out.

 

Fig7 shows edge connector 20 and also from Fig8 which is entitled Axlon Mod but Fig8 does D700 address access which is decidedly not the AXLON address so I don't know what to think about the pics or the text.

 

I've never done the upgrade acording to "THE ATARI 800 PLUS 256K" text file known as "PLUS256.TXT" on the same atr but I do have 2 such modded 800s only one of which actually works. Best of luck as my comps have additional jumpers not shown in Fig7, in particular bringing A14 and A15 to the middle board so that CFFF address access can be detected by the middle board.

 

Side note of minor importance - the original AXLON used 1FF0 thru 1FFF addresses for it's working register address with a shadow of that register at CFF0 thru CFFF. Which is why the axlon could even work in the middle slot when the middle slot can't see address CFFF at all. I like the mod as is on my 800 as it won't respond to any activity in the 1FF0 thru 1FFF region as a true AXLON board would, but the price for that is that the added memory can not just be dropped into any other 800 and work at all. It is a mod for the board and the machine as a pair.

 

Other files on that ATR have to do with that particular upgrade as well, so look it over real good.

[sup8pdct]

The series of .pic pictures on this atr are the only pictures I know of.

http://ape.dyndns.org:8083/UMICH/MODS/ADDMEMA.ATR

 

But that particular mod has trace cuts and mods shown for to use D700 address to bank the ramdisk instead of the more standard CFFF address so watch out.

 

Fig7 shows edge connector 20 and also from Fig8 which is entitled Axlon Mod but Fig8 does D700 address access which is decidedly not the AXLON address so I don't know what to think about the pics or the text.

 

I've never done the upgrade acording to "THE ATARI 800 PLUS 256K" text file known as "PLUS256.TXT" on the same atr but I do have 2 such modded 800s only one of which actually works. Best of luck as my comps have additional jumpers not shown in Fig7, in particular bringing A14 and A15 to the middle board so that CFFF address access can be detected by the middle board.

 

Side note of minor importance - the original AXLON used 1FF0 thru 1FFF addresses for it's working register address with a shadow of that register at CFF0 thru CFFF. Which is why the axlon could even work in the middle slot when the middle slot can't see address CFFF at all. I like the mod as is on my 800 as it won't respond to any activity in the 1FF0 thru 1FFF region as a true AXLON board would, but the price for that is that the added memory can not just be dropped into any other 800 and work at all. It is a mod for the board and the machine as a pair.

 

Other files on that ATR have to do with that particular upgrade as well, so look it over real good.

 

The one I have is axlon compatiable. A single wire needs to be soldered to the rom board so the switching address is at $CFFx I will need to find everything first!

 

James

[LYNXGUY]

It will help greatly if the covers are removed from all the ram modules and the os rom module.

 

The modules that I have are covered but if you need them or some of them I can mail them to you.

 

I can also take the uncovered modules from my 800 and replace them with the covered ones and my 800 should still work fine, I believe

[sup8pdct]

It will help greatly if the covers are removed from all the ram modules and the os rom module.

 

 

I can also take the uncovered modules from my 800 and replace them with the covered ones and my 800 should still work fine, I believe

 

The ones with covers clip into plastic bits on the sides of the case. The ones without covers are held with a single plastic spacer across the top of all boards.

It is best to stop all boards from moving or contact problems will arise due to movement and weird faults and hangups will happen.

 

James

[LYNXGUY]

The ones with covers clip into plastic bits on the sides of the case. The ones without covers are held with a single plastic spacer across the top of all boards.

It is best to stop all boards from moving or contact problems will arise due to movement and weird faults and hangups will happen.

 

James

 

I know that and I posted that to see if joejones needed and memory modules for his Atari 800 project and if they are not interchangeable then I will send him the modules that are covered for his Atari 800 project but I am sure the modules are interchangeable

[+Guitarman]

The cased and uncased 800 modules are the same. The cases were removed later on because of heat issues. If you have a cased memory module, you can remove it from the case and mod it.

 

If you are looking for extra 800 memory modules, I have 6-8 of them still in the box that I got in one of my acquisitions, if someone needs any.

 

I also have a Atari 800 with a Axalon compatible 288K upgrade that Scott Peterson personally built. It is the one with the 1 wire that goes to the OS card. If you need pics for reference for that upgrade, I can take some.