5 ms·

I knew a guy (Marc Crispin) who had a PDP-20 in his spare bedroom. His power bill was . . . large.

by kabdib 4y ago

dboreham 4y ago
Yeah an 11/70 needs 3-phase which I don't have.
- adrian_b 4y ago
  It is more important if you have enough electrical power available. Building or buying a 3-phase inverter or a power supply unit that could replace the original power supply are much easier tasks than building the logic boards of PDP-11/70, which you have. If the power requirements exceed what is available at your location, you could still make the PDP-11/70 work for very short times, by using a large enough UPS with a 3-phase inverter or with a substitute power supply, and charging the UPS, then starting the PDP-11/70 with the UPS disconnected from mains. The power requirements can be reduced a lot in comparison with a real PDP-11/70 if only the processor boards are used and the memory boards are replaced by a modern FPGA board implementing the protocol of the DEC memory bus. The maximum size of the PDP-11 memory (4 MB) is small enough that it can be implemented with the internal SRAM of many FPGA chips, no external DRAM memory is needed.
  - dboreham 4y ago
    > It is more important if you have enough electrical power available. I have 7.5KV in my yard so absolute power is not a problem. Good point about emulating memory and thereby getting away with a smaller PSU. Also need to emulate a disk drive. I have controllers for various drives but no physical drives (those are tricky to get working today even if they can be tracked down due to degradation of materials).
msla 4y ago
Where a "PDP-20" is a later version of a PDP-10, marketed as a DECSYSTEM-20 and intended by DEC to run TOPS-20.
- dekhn 4y ago
  oh. that was the first DEC I used- remember it from my childhood. It was replaced shortly after with a VAX/VMS machine. I fled to UNIX shortly after.

5 ms·

I knew a guy (Marc Crispin) who had a PDP-20 in his spare bedroom. His power bill was . . . large.

by kabdib 4y ago

I knew a guy (Marc Crispin) who had a PDP-20 in his spare bedroom. His power bill was . . . large.

dboreham 4y ago
Yeah an 11/70 needs 3-phase which I don't have.
- adrian_b 4y ago
  It is more important if you have enough electrical power available. Building or buying a 3-phase inverter or a power supply unit that could replace the original power supply are much easier tasks than building the logic boards of PDP-11/70, which you have. If the power requirements exceed what is available at your location, you could still make the PDP-11/70 work for very short times, by using a large enough UPS with a 3-phase inverter or with a substitute power supply, and charging the UPS, then starting the PDP-11/70 with the UPS disconnected from mains. The power requirements can be reduced a lot in comparison with a real PDP-11/70 if only the processor boards are used and the memory boards are replaced by a modern FPGA board implementing the protocol of the DEC memory bus. The maximum size of the PDP-11 memory (4 MB) is small enough that it can be implemented with the internal SRAM of many FPGA chips, no external DRAM memory is needed.
  - dboreham 4y ago
    > It is more important if you have enough electrical power available. I have 7.5KV in my yard so absolute power is not a problem. Good point about emulating memory and thereby getting away with a smaller PSU. Also need to emulate a disk drive. I have controllers for various drives but no physical drives (those are tricky to get working today even if they can be tracked down due to degradation of materials).
msla 4y ago
Where a "PDP-20" is a later version of a PDP-10, marketed as a DECSYSTEM-20 and intended by DEC to run TOPS-20.
- dekhn 4y ago
  oh. that was the first DEC I used- remember it from my childhood. It was replaced shortly after with a VAX/VMS machine. I fled to UNIX shortly after.