HP 9810



I am thinking about buying a HP 9810 with the basic memory configuration.
I have two questions:
Does someone know a way to add memory using market devices to reach its full potential?

Are such machine rare ? How much should i expect to pay for such a machine?



There's one on ebay right now:


I've seen 1 or two on ebay in the last year.


The memory in the 9810 is consists of Intel 1103 DRAM chips. These are 1K bit devices, and 3 of them are used for each block of program memory. Hardware in the memory cage does 2 physical accesses to the memory for each CPU memory access, and fiddles with the bits so that the 1K*3 physical memory appears as 512 6-bit 'program steps' to the CPU and to the user (the 9810 stores the program as 6 bit keycodes).
The 1103s are early PMOS memory chips and have strange supply rails (+16V and +19V) and logic levels. In the 9810, the TTL signals used by the rest of the machine are converted to/from these strange levels by circuitry on the memory timing/address/data PCBs -- the RAM PCBs are just the 1103 chips, and the signals at the RAM PCB edge connector are at these strange levels.
It is therefore non-trivial to use anything other than 1103s in the 9810. And I have no idea where you'd get those from these days.

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