RAMBO XL to Ultimate 1MB: Can it be done?

[SlagOMatic]

Back around 1986 I installed a RAMBO XL into my 800XL and have zero complaints about it, but now I'm considering the Ultimate 1MB upgrade for its additional features. The installation instructions for the Ultimate upgrade assume your machine is stock. Obviously mine is not. I can remove the RAMBO upgrade easily enough but the (socketed) memory chips in my 800XL are the 256K DRAMs that were required for the RAMBO, obviously not the original ones, and while I'm absolutely a pack rat I have no idea where those original DRAMs may be today.

 

If I were to install the Ultimate upgrade, would I have to replace the DRAMs in my 800XL with the original ones or can I keep the 256K DRAMs in there?

[ClausB]

You can keep the 256K chips. Just make sure to re-install R32 (3K).

[ClausB]

Although, if you have the older ANTIC in there, you should go back to 64K chips.

[TZJB]

19 hours ago, ClausB said:

You can keep the 256K chips. Just make sure to re-install R32 (3K).

 

R32 disables A8 of the DRAM by holding the pin 1s high. This allows the 256KB DRAM to be addressed as 64KB with the replacement of the RamboXL for a 74LS158 in U27 of course.

 

18 hours ago, ClausB said:

Although, if you have the older ANTIC in there, you should go back to 64K chips.

 

Good point. For clarity older ANTIC = C012296, new ANTIC = C021697.