Questions tagged [pdp-8]
For questions regarding the DEC PDP-8 minicomputer.
22 questions
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Which PDP-8 boot process variations did exist?
There's a general boot process for PDP-8, described in many documents at bitsavers.org. That includes first manually entering RIM bootloader through a control panel, running it to load BIN loader from ...
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10
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What typeface was used on the DEC PDP-8/F faceplate?
I'm currently working on a project to create a faceplate in the style of a Digital PDP-8/F. I'd like it to look the part and would love to find what typeface and font was used on the original.
The ...
- 201
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2
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DEC's "decimal ASCII"?
I'm reading some older FOCAL documents and see references to things like...
SETS X TO THE DECIMAL ASCII CODE OF THE INPUT CHARACTER
A bit later there is a table of these codes, and unless I am not ...
- 22.3k
7
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1
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Does the PDP-8/E service an interrupt after any instruction, or after instructions not referencing memory only?
While researching this answer about incrementing the program counter, I found something I thought was a little odd in the FETCH state flow diagram, which is figure 3-8 of the PDP-8/E & PDP-8/M &...
- 41.1k
10
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PDP-8 conditional skip and 2-word instructions
PDP-8 heavily relied on conditional skips: instructions that under some circumstances would skip the following instruction. Among them are, for example:
ISZ
SZA/SNA/etc. group of instructions
many IO ...
- 12k
10
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1
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PDP-8 floating point numbers
I'm trying to find a single clear statement of the limits to the numbers represented in the PDP-8's three-word format.
I found the original documents on this, but they are, ahem, not exactly ...
- 22.3k
11
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What is the difference (if any) between these two expressions in FOCAL?
I am trying to understand the 1969 FOCAL program Hamurabi in detail. The program was originally written for the PDP-8 version of FOCAL, but I am running it on the BK 0010-01 which presumably is a ...
- 3,123
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How did FOCAL convert strings to a number?
Reading over the manuals for FOCAL-69 and -71, as well as U/W-FOCAL, I realize there is one bit of the workings that I can't find an explanation for.
FOCAL did not have string variables, so to allow &...
- 22.3k
15
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2
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Did the PDP-8 designers consider a stack?
The PDP-8 was a remarkable exercise in minimalist computer design; some of the aspects of its design are discussed in detail at PDP-8 transistor count
One feature it did not have was a stack. Instead, ...
- 65.1k
2
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SAPCOL Japanese digital typesetting machines
In a comment to this question, Japanese SAPCOL digital typesetting machines are mentioned, which apparently used a PDP-8, and contained fonts for lots of Kanji.
What were those SAPCOL machines? What ...
- 34k
22
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Was the MC6800 based on the PDP-11 or PDP-8?
According to Gordon Bell, the 6800 was based on the PDP-11. According to Chuck Peddle, it was a PDP-8.
Can anyone with knowledge of the PDP's pass judgement?
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3
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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, ...
- 41.1k
3
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3
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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?
- 22.3k
5
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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 ...
- 41.1k
8
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1
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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 ...
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