37
votes
Accepted
Why are the Intel 8080's rotate instructions called opposite to intuition?
What historical reason is there for these instructions being called that?
"Historical Reason" is the right key word here, as ...
TL;DR: It's Piled Up Heritage
The 8080 inherited the ...
- 198k
27
votes
Accepted
Anyone up for decompiling some 8080 code for Kaleidoscope?
I had a look at the source and added a few comments (*1). Might not be the expected full high level abstract description, but should be still helpful as a first, tiny step to see its workings.
Doing ...
- 198k
25
votes
Anyone up for decompiling some 8080 code for Kaleidoscope?
Thanks to @Raffzahn commented code (in his answer) I was able to port the code into simple C++ code:
//---------------------------------------------------------------------------
const int VRAM_xs=64,...
- 7,044
19
votes
Accepted
Running CP/M on my own Intel 8080 emulator
Sounds like you got to go the same way as any system manufacturer back then:
Build your (virtual) Hardware.
CPU, RAM, ROM emulation
Some terminal connection
And at least some (virtual) mass storage ...
- 198k
12
votes
Accepted
Is there any known magic number signature for CP/M-80 program files?
At user Raffzahn's request, I've expanded a comment into an overly complex statistical answer. In summary, if a random *.COM file is 27392 bytes or fewer and starts with one of twelve byte values, it ...
- 19.3k
11
votes
Running CP/M on my own Intel 8080 emulator
You probably do not need to build CP/M from source. If you have a binary image you should be able to use that. But, you'll have to emulate the correct hardware for the build you have (since CP/M can ...
- 6,387
10
votes
Why are the Intel 8080's rotate instructions called opposite to intuition?
It can't be helping your intuition that that the official descriptions from the 1975 Intel 8080 Assembly Language Programming Manual, p.21, use the word "carry" in the descriptions only of ...
- 23.6k
8
votes
Long Term Prevalence of 8080 Code Over Z80 Code in Software Packages
Summary:
Are there any reliable numbers of the amount of Z80-only software for OS that supported both CPUs?
No, not previously, and not from third parties. I've had to rely on my own research here. ...
- 19.3k
8
votes
Why is the original Altair BASIC (for the 8080 CPU) source code not available on-line?
The original code was sold to MITS before it was even completed and teams from MITS and Micro-Soft both worked on it simultaneously. Bill and Paul both moved to Albuquerque to continue work. It was ...
6
votes
Were people building CPUs out of TTL logic prior to the 4004, 8080 and the 6800?
You ask about "people" -- I'll answer about myself.
In 1968, I build a "bit slice" ALU using transistors and diodes. I only built two bits of it, but it had an accumulator, two ...
- 737
5
votes
Is there any known magic number signature for CP/M-80 program files?
A process usually known as Magic Number or File Signature detection, intended to identify a file by looking at their first few bytes for certain values and/or structure.
As you have found out, there ...
- 36.6k
4
votes
Why are the Intel 8080's rotate instructions called opposite to intuition?
I think you are confusing the meaning of A in RAL/RAR it does not stand for accumulator but for arithmetic...
RLC/RRC are cyclic bit rotation (used for example for gfx movement by pixels)
and RAL/RAR ...
- 7,044
3
votes
Running CP/M on my own Intel 8080 emulator
While the source code to CP/M is available, the more usual method of bootstrapping CP/M on a new system uses a binary image (also available from www.cpm.z80.de) of the BDOS and other parts of CPM that ...
- 23.6k
3
votes
What are examples of providing non-RST instructions for 8080 interrupts?
An obvious answer is that any system including i8259 interrupt controller does generate CALL ADDR sequence for interrupt acknowledge.
See, for example, here: https://pdos.csail.mit.edu/6.828/2005/...
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2
votes
What are examples of providing non-RST instructions for 8080 interrupts?
Register or register pair increment or decrement commands (INR, INX, DCR or DCX) could be used for "transparent counting" of interrupt events while running something else. The code obviously ...
- 403
2
votes
Why did the 8080's PUSH PSW write one reserved bit as 1 and the other two as 0?
I'm looking into this repository https://github.com/1801BM1/vm80a, which have the original die photos of the KR580VM80A (a clone of i8080), its reverse-engineered transistor-level schematics and ...
- 9,709
2
votes
Were there any bitmap-based 8080 computers?
The Z80-based Camputers Lynx was notable for only having a bitmapped display, with no character-cell mode.
Because the graphics memory had to be manipulated during the horizontal and vertical sync ...
- 9,883
1
vote
Anyone up for decompiling some 8080 code for Kaleidoscope?
Ok, here is my Swift+SpriteKit version. I'd love it if someone could check the logic in the main updateKalidescope method.
Very annoying: in assembler, adding 200 to a register containing 200 is ...
- 18.5k
1
vote
Were there any bitmap-based 8080 computers?
Not a home computer per se, but the first time I messed with a bitmap display was modifying the rom of the original Space Invaders Arcade. It just used a straight b/w bitmap display with color ...
- 111
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