Max memory for 1200XL?

[BoatofCar]

I've been doing some exploring on Mr. Robot's TNFS server on Fujinet, and lots of modern games need 256k of XMS. I don't know what that means, but I want it! Is it possible to add more memory to a 1200XL, and if so, what is the max while being able to keep its original housing? 

[+x=usr(1536)]

Your best bet will be the Ultimate 1MB upgrade.  1MB of RAM and more.

 

Video showing the 1200XL install process:

 

 

[BoatofCar]

Thanks very much! 

[ACML]

Someone please correct me if I'm wrong, but don't you lose LED L1 and L2 functionality if the memory goes over 256K?  I think past 256K, you need the Port B that was for Joysticks 3&4 on the 400/800 and it is used to control the L1 & L2 LEDs on the 1200XL.  Something to consider.

 

[reifsnyderb]

54 minutes ago, ACML said:

Someone please correct me if I'm wrong, but don't you lose LED L1 and L2 functionality if the memory goes over 256K?  I think past 256K, you need the Port B that was for Joysticks 3&4 on the 400/800 and it is used to control the L1 & L2 LEDs on the 1200XL.  Something to consider.

 

PORTB bits 2 and 3 are used for banking.  On a 1200XL, PORTB bits 2 and 3 are used for the LEDs.  So any added banking messes with the LEDs.

[_The Doctor__]

so just accept the lights are now dual purpose as has been the case and move on, twinkle light changes are just a bank switch status instead of normal status... don't play with the leds for fun or you'll change the memory bank. This could be handled another way as well but it would be another modification.

[Rybags]

In theory the stock OS could mess with banking as a result of that dual use.  Later OSes still have that code but the key combos can't be generated since they don't exist on the other kbs.

[ACML]

44 minutes ago, Rybags said:

Later OSes still have that code but the key combos can't be generated since they don't exist on the other kbs.

I always run the 600/800XL OS as my primary OS in all my 1200XLs.  It has the best compatibility with software and as you state, it retains all the F1-F4 and LED functionality in the code.  It wasn't until the 130XE that Atari removed the LED/F key code from the OS.  I assume it was left in so the 1400XL/XLD could still utilize the LED/F key code.

The Rev 11 1200XL OS is more compatible than Rev 10 that shipped with all 1200XLs, but if you want maximum compatibility, replace the 1200XL OS with the 600/800XL OS.

 

[ACML]

51 minutes ago, Rybags said:

In theory the stock OS could mess with banking as a result of that dual use.

Are you saying that if one has more than 256K banking and I use the F1-4 key combinations, I might inadvertently mess up the banking since I'm forcing bits 2&3 high and low?

[Rybags]

Even the later XE OS that supports 128K in the RAM test retains the F-key code in the keyboard IRQ handler that can alter PORTB to reflect the relevant LED settings if the right F-keys are pressed.

I have a real 1200XL but it's just stock so I can't test it.  But I have no reason to believe that the memory config couldn't change.

When normal banking is active I would guess that nothing happens - only if the CPU and/or Antic are doing extended banking would it have an effect.

Edited January 28, 2023 by Rybags