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1500 questions
21
votes
5 answers
Was 1991's Hellcats the first instance of incremental screen updates?
In case you have never seen it, 1991's Hellcats was a seminal release on the Mac. It ran at full 8-bit color and could, on a newish machine, drive three 1024x768 screens at the same time. Nothing on the Mac or PC came remotely close.
I recall when I…
Maury Markowitz
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21
votes
6 answers
Which is the "equivalent bit-map resolution" of a Vectrex display?
I'm trying to replicate the Vectrex, but I don't want to deal with bare CRTs, death-level voltages and the like. So I need my Vectrex implementation to be able to be hooked to a regular CRT/LCD screen.
I am well aware of the vector nature of the…
mcleod_ideafix
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21
votes
5 answers
Why the disparity between the screencodes and the character codes?
The Commodore 64, and possibly others, I don't know, have character codes (These map integers to characters, in the same way that ASCII does) and there are screen codes (The offset which the VIC-II will use to look up the bitmap in the character…
Omar and Lorraine
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21
votes
4 answers
Would a C compiler for the Apollo Guidance Computer be plausible?
The Apollo Guidance Computer was used to control the command/service module and lunar module on the missions to the moon. (Definitely a retrocomputer!) As noted in this answer, programs were written in assembly language. There are several…
DrSheldon
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21
votes
1 answer
What was the reason for the ZX Spectrum's display bitmap layout?
I had a ZX Spectrum 48KB, whose display was a 256*192 monochrome bitmap (plus separate per-block color attributes). I remember the display bitmaps scan lines were laid out in memory in a weird way - This was evident when trying to render to the…
Jonathan
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21
votes
3 answers
Why use repeated STZ instructions with the same operand on the 65C816 for the SNES (Super Nintendo)?
Please consider the code in Super NES Programming/Initialization Tutorial/Snes Init.
Here is an excerpt:
stz $2113 ; Plane 3 scroll x (first 8 bits)
stz $2113 ; Plane 3 scroll x (last 3 bits) #$0 - #$07ff
From the comments, this seems…
AlphaCentauri
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21
votes
8 answers
Uses for the halt instruction?
What was the halt instruction in early CPUs such as the Z80 and 8080 used for?
Here's a description of the Z80 instruction:
The HALT instruction suspends CPU operation until a interrupt or reset is received.
While in the halted state, the…
Jet Blue
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21
votes
3 answers
Native C compiler for Sinclair ZX Spectrum
I am looking for a native C compiler for the Spectrum 128. I would like one which:
Has good support for the latest C standard at the time.
Is not limited to compiling ridiculously short source code.
Produces decently-optimized machine code*,…
forest
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21
votes
5 answers
Size of the PDP-8
What is the physical size of a PDP-8? The photographs I found seem to be evenly divided between showing it as a compact unit that looks maybe one foot high, and as a tall cabinet maybe five or six feet high.
Conjecture: the different sizes…
rwallace
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21
votes
6 answers
Understanding INKEY$ in ZX BASIC
The ZX BASIC Manual gives the following little program to demonstrate how INKEY$ works:
10 IF INKEY$ <> "" THEN GO TO 10
20 IF INKEY$ = "" THEN GO TO 20
30 PRINT INKEY$;
40 GO TO 10
While I have ascertained that this works, and that if you…
harlandski
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21
votes
9 answers
Formatting a 720K floppy disk over USB fails with Windows 10
I've read many times that USB floppy drives will not format (or read/write) 720K disks. But then I read several posts online where people say they have done it. Even with Windows 10 (which is what I'm using).
One instance said to use the following…
cbmeeks
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21
votes
3 answers
What is causing the problem with the RAM in this (claimed) Spectrum 48k?
I bought what was claimed by the seller to be an Issue 4S Spectrum 48k.
I tried loading games and some worked while others didn't. Turns out it was the 16k ones that worked and 48k didn't. This pattern took a while to work out because the tapes were…
popeymon
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21
votes
5 answers
How were binary subroutines embedded in Integer BASIC programs?
Programs written in Apple's Integer BASIC sometimes had bits of machine code embedded in them. This was more convenient than loading the code separately, especially when the program was loaded from tape.
When the program is first loaded, it looks…
fadden
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21
votes
6 answers
How can I emulate MS-DOS on OS X?
I am looking for a emulator for MS-DOS for OS X to run old games on.
Are there any free emulators for MS-DOS that run on an Apple machine with OS X?
user448
21
votes
4 answers
Obscure uses of the Commodore 8050/1541 disk drive
When I was working for a foundry consultancy, we did the following
Download routines to add delays when writing certain tracks. This was a security feature. When the program started, it would try to read that track normally. If it could, it…
cup
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