Newest Questions
6,685 questions
4
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Original IBM PC arrow keys (Dataperfect)
Am playing around with Dataperfect, and have noticed a problem, which seems to be alluded to here also.
Data Perfect uses the shift and arrow keys in order to move from field
to field on fields that ...
- 2,231
13
votes
1
answer
290
views
Why did the 8087's constant ROM contain the value ln(2)/3?
In the post Extracting ROM constants from the 8087 math coprocessor's die , the constant ROM from the Intel 8087 was reverse engineered and all 42 constants extracted. One of these constants is 1....
- 2,259
-1
votes
0
answers
179
views
Please help to identify presumably a piece of old computer equipment in a video [closed]
Can anybody recognize this? https://youtu.be/bR1pGF2XOMw?t=112 Looks like disk drives.
Edit: Image from the original link:
Other shots of this device from the official music video, showing the whole ...
- 9
13
votes
1
answer
1k
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What was the Servus 100 system?
All I've got is a picture of the Servus 7771 terminal, which was apparently used to access the Servus 100 host (whose manual is visible on the photo):
There appears to be nothing on the web about ...
- 889
33
votes
1
answer
3k
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Was the second copy of the FAT ever used for anything?
As I remember, DOS had to update a backup copy of the FAT with each disk write, which I imagine would have greatly slowed write speed. Yet I don't recall any recovery software that used the second ...
- 4,783
6
votes
0
answers
202
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What keyboard switches are used for the toggle keys in the C128 DCR detachable keyboard?
The Commodore 128 keyboard has, in addition to the normal keys, three mechanical toggle switches: SHIFT LOCK, CAPS LOCK (ASCII/DIN in the German model) and 40/80 DISP. One of them broke apart on my ...
- 1,188
10
votes
1
answer
663
views
What size belt to buy for the Atari 1010 program recorder?
I got a nice Atari 600XL with a 1010 "Program Recorder" (cassette player). Too bad the motor drive belt broke and I am now trying to find a good replacement. I already tried a square belt, ...
- 1,389
10
votes
2
answers
1k
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What form factor did the first-gen "compact Mac" HDDs use?
When I was growing up I had access to a Mac Classic fully kitted out with a full 4MB of RAM and an internal SCSI 40MB hard drive. I never got to open the thing up (and wouldn't have known how to do so ...
- 205
15
votes
1
answer
573
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Did CRAY's computers have a guard bit?
The paper What Every Computer Scientist Should Know About Floating-Point Arithmetic uses the Cray's systems as an example of computers without a guard bit:
Although most modern computers have a guard ...
- 153
18
votes
6
answers
3k
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How were large UNIX installs managed in the 80s/90s?
Nowadays, you can use Ansible, Chef, Salt and others, to manage Linux/*BSD systems, keep them updated, install software in a reproducible way etc...
What tools were used to manage large UNIX installs (...
- 979
16
votes
4
answers
4k
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Did DOS on the early, slow machines ever fail to handle interrupts timely, and what happened if it did?
DOS on the 8088 had to process interrupts and return. If a higher-priority interrupt occurred, the current handler was pushed and the higher-priority interrupt was serviced.
4.77 million seems like a ...
- 4,783
3
votes
0
answers
162
views
Looking for TRS-80 4P terminal emulation software
I have a TRS-80 4P that works beautifully, and I'd love to set it up as a terminal to other equipment I own (a Linux server, or a PiDP-11), but I'm having trouble finding actual, functional terminal ...
- 31
10
votes
2
answers
1k
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New to Amiga, my machine wants some floppy, no workbench but kickstart in ROM [closed]
My new Amiga, running as an "fs-uae" process on an Ubuntu laptop, stops here:
My impression is that it wants a disk. After a lot of investigation, I understood that kickstart (ca. "...
- 1,924
0
votes
1
answer
139
views
Connect Epson HX-20 to PC via MAX3232 board
This question follows on from my previous one, but I'm trying to make things a bit simpler for myself for now, and first of all connect my now working HX-20 to an old PC which has a nine pin serial/...
- 3,215
6
votes
2
answers
653
views
RS232 to connect to Terminal from Epson HX-20?
Please note this is a different question from this one of mine from six years ago.
So I acquired a second Epson HX-20 with a view to hopefully being able to put together one working computer from the ...
- 3,215
0
votes
0
answers
210
views
MegaTech arcade board - video compatibility with LCDs
Is video output from Megatech Arcade board compatible with contemporary digital monitors (or analog to HDMI upscalers)?
My board was working at seller's side (I have a video as a proof), but he tested ...
- 81
5
votes
2
answers
2k
views
What's the name of this "Burroughs" computer?
I was watching "You Only Live Twice" (1967), and I saw this "Burroughs" computer:
What's the name of this "Burroughs" computer?
- 307
12
votes
3
answers
2k
views
How did old programs handle signal safety when there weren't the POSIX realtime signal extension?
This could be at cross section of {Unix,LangDev,RetroComp}.SE, but I'll give it a try at here first.
Majority of the functions (many section 3 user-space interfaces, not the section 2 system calls) in ...
- 499
9
votes
2
answers
1k
views
In the 8088, what was the time/cycles penalty for switching segments?
If the penalty was 0, then you have a flat 640K. But it wasn't zero, so what was it?
I get the feeling from reading about it that segment switching was something to be avoided at almost any cost.
- 4,783
5
votes
0
answers
368
views
What's the advantage of replacing DOS/4GW with DOS/32A?
Introduction
As far as I understand, DOS/4GW was the thing that allowed most games from MS-DOS era to access beyond the 640KB conventional memory limit. (For completeness, there was also EMS and XMS, ...
- 151
10
votes
2
answers
2k
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Is it possible to switch from 32-bit protected mode to real mode without going through 16-bit protected mode?
The OSDev wiki talks about a need for an intermediary 16-bit protected mode.
I tried a direct switch many different ways and it just caused a crash, because it still executed 32-bit instruction after ...
2
votes
1
answer
444
views
Way to implement multi threading on a MOS 6502 type CPU [closed]
I'm trying to write an OS for the W65C02 CPU but i'm stuck because I have no idea on how to implement concurrency on such old CPU.
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4
votes
1
answer
365
views
What's the difference between `FNINIT`, `EMMS` and `FEMMS`
To use the x87 coprocessor, one has to use the FINIT or FNINIT instructions (FINIT is, as far as I know, just FWAIT followed by FNINIT). This sets the control word to a valid state, and sets all the ...
8
votes
0
answers
348
views
What were the last C & C++ compilers to support automatic MMX vectorisation?
It was suggested to me to move this question from SO to here.
There was a relatively short (in tech terms, at least) period during which MMX was the only way to vectorise integer operations on the x86,...
7
votes
0
answers
285
views
Z80 Memory Bank Switching
Edit: sorry it's so many words. I thought it might be helpful to share as much as I have learned so far as possible.
Also, here's the link to service manual that includes the schematics.
https://www....
- 71
0
votes
1
answer
217
views
Trying to identify an older pc game from the 80's
Joystick + fire button: Classic arcade control.
Player ship moves left to right: Fixed shooter format.
Bugs load from the top like a conveyor belt, move horizontally, then drop into vertical lanes....
6
votes
1
answer
331
views
Is there any extant documentation for the MTS fmt formatting program?
Turns out that the original, machine-readable markup form of the Revised Report on the Algorithmic Language Algol 68 is online, hosted by Dick Grune. It is filled with incantations and weird syntax. ...
- 3,930
2
votes
0
answers
100
views
PDA Acer N50 battery pinout
Could you please summarize pinout (voltage levels and potentially a communication protocol if applicable) of PDA Acer n50 battery? I haven't found any spec in Google and AI provides just nonsense ...
- 81
1
vote
0
answers
168
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IBM S/38 ROS (rom) images availability?
Due to recent references to IBM’s S/38, I was pondering the possibility of doing an emulator. There seems to be adequate hardware information but the roms would be required. Did images of the various ...
- 295
6
votes
0
answers
264
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What were the mistakes made during Intel Merced (Itanium) development that caused the delay from 1999 to 2001? [closed]
I’ve seen allusions to them wasting time trying to make 250nm Merced work and them not laying each module sequentially in early development but trying to lay it out all at once, and having too many ...
5
votes
1
answer
234
views
How to address MEGA65 memory above 64 KB in VBCC?
Could you please help me to address MEGA65 memory above 64 KB using VBCC compiler?
Below example of changing color attribute of a character works just for memory below 16-bit address space:
#define ...
- 81
4
votes
2
answers
306
views
How to run a Java Applet in the browser?
I am trying to run a Java Applet in the browser, but since it is now 2025, it obviously fails.
Things that I tried:
I installed lubuntu-14-04, using QEMU/KVM, but the browser immediately updated to ...
- 141
1
vote
0
answers
89
views
Minix 1.6 disk images
I'm looking for Minix 1.6 disk images for i386 or i86 (16-bit x86). The disk image can be an installer, a demo floppy, or a HDD image of an already installed system.
I know about Minix-386vm 1.6.26.1, ...
- 5,499
10
votes
5
answers
2k
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Did any processor ISA have a "reversed accumulator" architecture?
Simple processors (microprocessors or otherwise, especially older ones) often have an accumulator register that serves as the implicit source/destination register for instructions. In a microprocessor ...
- 1,069
5
votes
0
answers
395
views
What happened to the Amoeba operating system?
It's about the distributed Unix-like Amoeba OS developed at the Free University of Amsterdam by Andrew Tanenbaum: Since the late 1990, there seems to have been no measureable progress in development. ...
- 889
15
votes
2
answers
2k
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How does using a two-phase clock allow the processor to use latches instead of flip flops?
When reading about the MC6800 somewhere, I remember it being stated that a two-phase clock signal was used because it allowed the designers of the processor (as well as many other older MPUs) to use ...
- 401
4
votes
0
answers
208
views
Which game is this?
From Visitors serie, episode 17, minute 27 circa. Willy and young friend are playing a video game, which game is this?
Is not Captain commando, is very similar (but is not) to Chicago coin commando, ...
- 3,497
3
votes
0
answers
164
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Did you use BookManager on IBM big iron for internal documentation
I was trying to remember what I was using back in the early 90s for internal documentation at IBM back in the day. I worked at a site in Tampa that housed 3090 mainframes and was using VM/CMS.
Does ...
6
votes
0
answers
223
views
Did any notable 6502 systems coordinate DMA with start of instruction rather than adding delay for possible writes?
An annoying hardware quirk of the 6502 is that while the READY line can be used to extend read operations, it cannot be used likewise for writes. As a result, systems which need to accommodate DMA ...
- 41.2k
13
votes
2
answers
2k
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What's this weird floating-point format in SPARC
I see some instructions operating on this extended format in SPARC V7
FADDx
Add Extended (FPU Instruction Only)
Operation:
f[rd]x ← f[rs1]x + f[rs2]x
Assembler Syntax:
faddx fregrs1, fregrs2, fregrd
...
- 4,091
8
votes
1
answer
551
views
"Paul's method" moniker for the 6502 RTS trick
In 6502 assembly programming, there's a common trick (usually called the RTS trick) for performing indirect jumps by pushing the target address minus one on the stack and executing a RTS instruction. ...
- 331
1
vote
3
answers
422
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How to automatically set the random seed in Microsoft Z80 BASIC?
I am trying to find a way to automatically set the random seed in Microsoft Z80 Basic 4.7b on an RC 2014, as one would in Sinclair BASIC with RAND or RANDOMIZE.
I have got as far as understanding that ...
- 3,215
1
vote
0
answers
137
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What is the earliest use of hex triplets for representing color? [duplicate]
I am specifically asking about the syntax #RRGGBB as it is still used in CSS.
The earliest use I can find is in the X10 Window system, which shipped a color definition file with hex triplets in 1986. ...
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6
votes
2
answers
314
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How do I make Minix 1.5 8086 boot from a hard drive?
I'm trying to install Minix 1.5 in an emulator. I've made good progress: I've prepared and populated 2 partitions on the HDD image, I can boot the kernel from floppy image demo_dsk.ibm or disk.03, ...
- 5,499
2
votes
1
answer
613
views
Where to get the Minix 1.5 demonstration disk for 8086?
I'd like to get the Minix 1.5 demonstration disk for the 8086, preferably as floppy image which I can boot in an emulator. The demonstration disk is mentioned in this offical document.
The official ...
- 5,499
1
vote
1
answer
168
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ROM chip width to match 18-bit CPU [closed]
Early microprocessors typically had data bus width of 8 bits. Dynamic RAM chips were typically 1 bit wide, used in rows of 8, but mask ROM chips were typically 8 bits wide. As I understand it, this ...
- 65.3k
11
votes
7
answers
4k
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What was the minimum amount of addressable memory? When and why did computers become byte-addressable?
I'm watching this video, which, at 9:51, says that around the late 1980s the majority of computers were byte-addressable.
So the minimum amount of data you can retrieve from RAM was 8 bits.
What was ...
- 571
10
votes
2
answers
2k
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How is the parity bit in tape storage computed?
I'm watching this video and at 5:04 it says that old cassette tape store 1 byte as 7 bit of information and a leading parity bit that could tell whether a bit of information was flipped.
How was that ...
- 571
15
votes
3
answers
1k
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Operating systems running programs in 286 16-bit protected mode
I'm looking for existing, old operating systems which can run programs in 286 16-bit protected mode. (Please note that in this question I'm not interested in 16-bit programs for the 8086 and 80186, or ...
- 5,499
7
votes
1
answer
517
views
Transistor count for the General Instrument AY-3-8910?
I'm going to be adding infoboxes to some of the classic stand-alone chips on the Wiki. I'm starting with sound chips. I could not find a transistor count for the AY8910. Can anyone find one?
Normally ...
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