+bob1200xl Posted February 23, 2011 Share Posted February 23, 2011 This is my latest 512K upgrade for the 1200XL. It requires the 800XL OS mod, 3 more board wires and the 5 PBx wires. (no PCB cuts, so you can remove it easily) You end up with 512K (battery-backed) in addition to the original 64K. I have a couple of spare boards... Bob Quote Link to comment Share on other sites More sharing options...
jamesk Posted February 23, 2011 Share Posted February 23, 2011 Very clean looking work Quote Link to comment Share on other sites More sharing options...
+wood_jl Posted February 23, 2011 Share Posted February 23, 2011 (edited) [envious of your skills] That's awesome! So the RAMdisk (or whatever) maintains its contents? Wondering how the battery works. [/envy] Edited February 23, 2011 by wood_jl Quote Link to comment Share on other sites More sharing options...
+bob1200xl Posted February 23, 2011 Author Share Posted February 23, 2011 Yes, the data in the SRAM does not go away when you power off. If the voltage from the system drops below 3.5v, the controller chip kills access to the chip - so the data doesn't get corrupted. The coin cell provides enough power to keep the data in the SRAM. It makes kind of a cute, 512K disk drive, where you don't have to worry about your program crashing and losing your data. Bob [envious of your skills] That's awesome! So the RAMdisk (or whatever) maintains its contents? Wondering how the battery works. [/envy] Quote Link to comment Share on other sites More sharing options...
+Larry Posted February 23, 2011 Share Posted February 23, 2011 Hi Bob- Very nice! Very compact and with few connecting wires. The controller chip is under the ribbon cable? Presume you are planning on putting together a .doc file so they can be built? Any additional issues in putting it in an 800XL? What does the ram emulate -- or does it use it's own driver to create another kind of ramdisk? -Larry Yes, the data in the SRAM does not go away when you power off. If the voltage from the system drops below 3.5v, the controller chip kills access to the chip - so the data doesn't get corrupted. The coin cell provides enough power to keep the data in the SRAM. It makes kind of a cute, 512K disk drive, where you don't have to worry about your program crashing and losing your data. Bob Quote Link to comment Share on other sites More sharing options...
+bob1200xl Posted February 23, 2011 Author Share Posted February 23, 2011 The controller chip is a DS1210. (SRAM de-volitizer) There is no code or such for this - it is a standard RAMBO, using bits 1-3 and 5-6. I programmed the MMU to do the SRAM selection, so there is no other logic in the upgrade. This is a physical and logical build of the SRAM/PBI board with only the SRAM portion. I can post the instructions. Bob Hi Bob- Very nice! Very compact and with few connecting wires. The controller chip is under the ribbon cable? Presume you are planning on putting together a .doc file so they can be built? Any additional issues in putting it in an 800XL? What does the ram emulate -- or does it use it's own driver to create another kind of ramdisk? -Larry Yes, the data in the SRAM does not go away when you power off. If the voltage from the system drops below 3.5v, the controller chip kills access to the chip - so the data doesn't get corrupted. The coin cell provides enough power to keep the data in the SRAM. It makes kind of a cute, 512K disk drive, where you don't have to worry about your program crashing and losing your data. Bob Quote Link to comment Share on other sites More sharing options...
FastRobPlus Posted February 23, 2011 Share Posted February 23, 2011 This is terrific! Are you selling the boards? Quote Link to comment Share on other sites More sharing options...
+bob1200xl Posted February 24, 2011 Author Share Posted February 24, 2011 I have 4 extra boards that I could sell, naked - no parts on them - $20, built and tested - $50. You would also need the MMU and EPROM from me. (unless you can program such things) Here are the instructions, which include the OS conversion: Pull the 24-pin OS sockets, U12 and U13. (if you already have 28-pin sockets, skip this part) If you want a dual OS that is selected by the TV CHAN switch, cut the land on the PCB between pin 27 and pin 28 on U13. Solder a wire from either side of L14 (up by the CHAN switch) to this pin 27. (on the bottom of the board) Pull all the W jumpers except W11 and W12. If W11 and W12 are empty, add jumpers. Solder a wire on the bottom of the board from CPU - pin 23 to the top of W6. (the end of W6 that does not go to +5v) Solder a wire from CPU-36 to U12-20. Solder a wire from CPU-39 to MMU-18. Solder a wire from MMU-14 to 6520-14. Solder the flat cable to 6520 pins 11, 12, 13, 15, and 16. (order does not matter) Plug the new OS EPROM into U13. Plug the new MMU into U18. Connect the flat cable to the new board and plug the new board into U12. Done... run tests. This is terrific! Are you selling the boards? Quote Link to comment Share on other sites More sharing options...
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