600XL - Upgrade to 64KB
Posted: 12 Mar 2022 16:34
Having just upgraded my 600XL to 64KB, a step needed before installing the Ultimate 1MB upgrade, I thought I would share it so that all could benefit from the relatively easy process.
You will need 2x D41464 64KB RAM chips (or equivalent), with a speed at least equivalent to the speed of the old 16KB ram you are replacing. For example, my old 16KB RAM was 150ns, the new 64KB was 100ns.
If any of the ICs you need to work with are soldered in, rather than socketed, I would advise you carefully remove them and fit sockets first and test the machine still runs before proceeding. Most 600XLs seem to be socketed so you will probably be OK.
Before proceeding, remove the 2 16KBx4bit RAM ICs and insert the 2 replacement 64KBx4bit RAM ICs and ensure the machine still runs as expected and shows only 16KB.
Start of by desoldering the front lead of R36. R36 is the resistor closest to the right hand end of the two RAM chips.
You will need to lift the the following pins of the specified ICs and connect as directed:
Lift U6 pin 10 and connect to the PCB as per the lower red wire.
Lift U5 pin 3 and connect to the PCB as per the black wire.
Lift U16 pin 8 and connect to the forward end of resistor R36 as per the top red wire.
Full details of connection are as per the following picture:
Once installed as above, test the RAM as you see fit, here I have done so with the SuperSalt cartridge:
You can however either run the internal Self Test by booting with Option held down, and selecting the memory test. If all is well you should see 50 green blocks on the screen, 2 for ROM and 48 for RAM. Any bad blocks will appear red. The white block here is the one currently being tested.
Or type "PRINT FRE(0)" at the basic prompt and hit enter. You should get the result 37902 if all is well.
You will need 2x D41464 64KB RAM chips (or equivalent), with a speed at least equivalent to the speed of the old 16KB ram you are replacing. For example, my old 16KB RAM was 150ns, the new 64KB was 100ns.
If any of the ICs you need to work with are soldered in, rather than socketed, I would advise you carefully remove them and fit sockets first and test the machine still runs before proceeding. Most 600XLs seem to be socketed so you will probably be OK.
Before proceeding, remove the 2 16KBx4bit RAM ICs and insert the 2 replacement 64KBx4bit RAM ICs and ensure the machine still runs as expected and shows only 16KB.
Start of by desoldering the front lead of R36. R36 is the resistor closest to the right hand end of the two RAM chips.
You will need to lift the the following pins of the specified ICs and connect as directed:
Lift U6 pin 10 and connect to the PCB as per the lower red wire.
Lift U5 pin 3 and connect to the PCB as per the black wire.
Lift U16 pin 8 and connect to the forward end of resistor R36 as per the top red wire.
Full details of connection are as per the following picture:
Once installed as above, test the RAM as you see fit, here I have done so with the SuperSalt cartridge:
You can however either run the internal Self Test by booting with Option held down, and selecting the memory test. If all is well you should see 50 green blocks on the screen, 2 for ROM and 48 for RAM. Any bad blocks will appear red. The white block here is the one currently being tested.
Or type "PRINT FRE(0)" at the basic prompt and hit enter. You should get the result 37902 if all is well.