Questions tagged [pdp-8]
For questions regarding the DEC PDP-8 minicomputer.
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What happens on the Straight-8 when changing to a non-existant data field?
The extended memory controller on the PDP-8 (the original one, sometimes called the Straight-8) apparently had difficulty when selecting a datafield that didn't exist:
On machines with 8K or more, ...
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vote
3answers
208 views
Was 1.10 a valid line number in FOCAL?
I'm looking over examples of FOCAL code, and I see that group numbers in the examples start with a 0 if need be. That is, it's 01.10, not 1.10. Was a leading zero optional?
5
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3answers
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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
199 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
196 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
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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
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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 ...
10
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3answers
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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
528 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
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3answers
673 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 ...
