Retrocomputing Beta

Questions tagged [pdp-8]

Ask Question

For questions regarding the DEC PDP-8 minicomputer.

9 questions
Newest
Active
Bountied
Unanswered
Filter by
Sorted by
Tagged with
3
votes
2answers
156 views

In what way does the Straight-8 expand on the PDP-5?

A quote from the Wikipedia: The PDP-5's instruction set was later expanded in its successor, the PDP-8, to handle more bit rotations and to increase the maximum memory size from 4K words to 32K ...
8
votes
1answer
180 views

Are there any PDP-8 assemblers that create linkable object files?

I am currently writing a compiler for the PDP-8. The compiler is going to translate source code into PDP-8 assembly code that calls some runtime routines to perform high-level functions such as ...
4
votes
2answers
167 views

Does the Intersil 6100 do interrupts differently from other PDP-8s?

As I recall, the original PDP-8 actually does a jsr 0000 when an interrupt happens, so that the interrupt service routine started at address 0001. I think that saves a few gates, since the instruction ...
18
votes
4answers
2k views

Size of the PDP-8

What is the physical size of a PDP-8? The photographs I found seem to be evenly divided between showing it as a compact unit that looks maybe one foot high, and as a tall cabinet maybe five or six ...
10
votes
4answers
1k views

PDP-8 transistor count

https://en.wikipedia.org/wiki/Transistor_count provides some transistor count figures for early microprocessors, e.g. 8008 and 6502 both listed at around 3500. The PDP-8 was a 12-bit computer with a ...
9
votes
3answers
1k views

How did the PDP-8 handle strings?

The PDP-8 was a popular 12-bit minicomputer of the late sixties. It used word addressing, so that it always dealt in 12-bit words, of which it could address 4096 with a full bank of core memory. In ...
7
votes
3answers
487 views

Arithmetic operations on multiple words on the PDP-8

For the PDP-8 with its strange ISA, I've always wondered what the "standard" (i.e. fastest) way to do arithmetic operations (add, subtract, maybe multiply) on integers consisting of multiple words was....
14
votes
3answers
646 views

Conditional skip instructions of the PDP-8

I am interested in the SKIP instructions on the PDP-8. These test the accumulator and Link bit, and they skip the next instruction if the condition holds. The instructions are: OR GROUP SMA - Skip ...
23
votes
4answers
2k views

Use of undocumented opcodes

I figure this is fitting for Retrocomputing.SE because CPUs like the 6502 and Z80 and the PDP-8, and probably others, have undocumented instructions and will happily execute them, in contrast with ...