Upgrading my HP9816

I've just upgraded my HP9816 (aka HP9000/216) to have 1M RAM on the processor board,. In case anyone else has one of these machines, and wants to do the upgrade, here's how I did it. -tony Upgrading an HP9816 to 1M RAM on the processor board ---------------------------------------------------- These instructions assume you're starting with a 256K processor board, that is one with 32 4164 DRAMs fitted. Firslty remove the processor board. To do this, disconnect all cables board witu an external connector). Remove any DIO boards in the slots -- memory voards will need to have their addresses chaged after this modification. Release the 2 quarter-turn fasteners on the rear of the machine and free the top cover from the clips under the back edge of the machine. Slide the cover rearwards, lift it off, and unplug the fan cable the machine -- rearwards, unclip the earth wire fromthe faston tab on the RS232 connector. Slide the processor board all the way out. Now to upgrade the RAM. Desolder all 32 DRAMs from the board. These are in 2 rows at the very front edge. Leave the clock oscillator can, reset-circuit transsitor array, and resistor pack in place. Clear out the pads for U122 (to the right of the rear row of DRAMs) and R47 (leftmost resistor in the block of 3 resisotrs to the left of the ROMs) At this stage both of those locations should be empty. Fit 32 41256 (256K*1) DRAMs in place of the 64K ones that were just removed. Fit a 74F158 at U122 and a 33 Ohm resistor at R47 Cut J11 and J12 (in front of the DIP switch array). Cut J8 1-2 and link 2-3 (this likn is in fornt of U34, near the ROMs). Turn off all sections of SW3 (frontmost DIP switch). Sections 5-7 _must_ be off or the RMA will be diabled, sections 1-4 set the address of the RAM. It's simplest to have them all off, which makes the processor board RAM appear at the top of the memory map, then to address all other boards following the HP instructions, regarding the processor board RAM as a 1M board set to '0'. Refit the processor board, conencting the ground wire. Plug in the mains cable and power up. The screen should report a little under 1M free. If all appeears to be working, switch the unit off, unplug the mains cable, and refit the covers, DIO board(s) and cables.