All Questions
1,041
questions
96
votes
11
answers
14k
views
What key factor led to the sudden commercial success of MS Windows with v3.0?
Microsoft Windows was originally introduced in 1985, ostensibly to compete with the Apple Macintosh, and other computers shipping with graphical shells by that time. However, early versions of Windows ...
- 60.1k
62
votes
3
answers
7k
views
How does the LOADALL instruction on the 80286 work?
This undocumented instruction existed in the 80286 and, I believe, the 80386. I think it was added while debugging the chip, so the engineers could quickly put the processor into any state and test it ...
- 18.6k
108
votes
10
answers
42k
views
Why do C to Z80 compilers produce poor code?
When reading some other questions about compiling C for the Z80,
How much benefit should be expected on a more advanced compiler for z80/r800 based computers?
Native C compiler for Sinclair ZX ...
- 38.2k
59
votes
9
answers
13k
views
What was the rationale behind 36 bit computer architectures?
Was there some particular design theory or constraint that made a 36 bit word size attractive for early computers? As opposed to the various power-of-2 word sizes which seem to have won out?
- 875
36
votes
3
answers
13k
views
What modification is required from a PC floppy for use in Amiga?
Around the end of the time of Amiga popularity, obtaining a replacement Amiga floppy drive was a nuisance, while PC drives were ubiquitous and cheap. One could install a PC drive in Amiga after ...
- 7,075
33
votes
6
answers
31k
views
Windows 98 with 2GB of RAM
I have assembled a retro-gaming PC out of an old Shuttle SN45G with a Windows 98/Windows XP dual boot.
The motherboard can handle 2GB of RAM, but apparently Windows 98 can only handle 1 GiB.
Windows ...
- 2,637
28
votes
2
answers
4k
views
How did an IBM 5150 with 16KB RAM work?
I keep reading that when it was first released, there was a variant of the IBM PC model 5150 that had only 16KB of RAM installed. From a hardware perspective, this would clearly work - the 5150 ...
- 12.8k
25
votes
4
answers
6k
views
Z8410 DMA chip as GPU?
There are basically two ways to design a 2D graphics system:
Provide lots of hardware support in the form of tiles, hardware scrolling and sprites, to put together each frame on the fly from a small ...
- 58.4k
60
votes
3
answers
16k
views
Who set the 640K limit?
We all know that "640K should be enough for everyone". But who actually set this limit? The quote is often attributed to Bill Gates, but it doesn't seem like a decision for an Operating System vendor ...
- 939
46
votes
4
answers
41k
views
Commodore 64 to modern TV
I've been thinking about getting a Commodore 64 machine. However, I realise there's obviously no video cables I have that will work. But when I looked online there are many people using S-Video to VGA ...
- 563
33
votes
3
answers
5k
views
Reconditioning and cleaning old Nintendo (and other) game cartridges
I used to blow the dust out of the cartridges but I heard that can actually damage the cartridge or the system itself.
I am looking for the proper way to clean old Nintendo game cartridges (such as ...
- 439
33
votes
4
answers
16k
views
What exactly is a cycle-accurate emulator?
Emulators such as Higan are cycle-accurate and thus have full compatibility with all existing software. In a 2011 Ars Technica article, much was said about cycle accuracy and how it preserves games by ...
- 1,838
17
votes
5
answers
4k
views
What tools were used in late MS-DOS era for reverse engineering and patching binary executables?
In the late MS-DOS era, what were the state of the art software tools for reverse engineering and patching binaries, i.e. .exe and .com files?
A simple list of the tools that were "state of the art", ...
- 1,463
15
votes
6
answers
7k
views
How can I adapt a digital CGA/C128 signal (RGBI DE-9) to a modern monitor?
IBM's CGA and the Commodore 128's RGB video output both use a DE-9 connector. How do I adapt the CGA video output from an IBM XT 5160 or Commodore 128 to a modern monitor?
- 17.4k
11
votes
4
answers
11k
views
How do I create a boot menu to select between Windows and DOS?
I was not a PC user before Windows 98. But I remember one of my friends was using a boot menu in his 486 machine to select between Windows/DOS.
The menu was like:
1. EMS
2. XMS
3. Windows
If we ...
- 2,728
147
votes
5
answers
51k
views
It's now safe to turn off your computer
One thing I remember very well from my childhood is the screen you got at the end of a shutdown process on old computers:
I don't know if this was a Windows 95/98/2000/ME only thing but I wonder why ...
- 1,341
98
votes
1
answer
29k
views
Why did MS-DOS applications built using Turbo Pascal fail to start with a division by zero error on faster systems?
On faster MS-DOS systems, it wasn't entirely uncommon for applications built using Borland's Turbo Pascal to fail to start, and (before exiting back to the command prompt) to report a division by zero ...
- 5,246
73
votes
8
answers
23k
views
Which Linux or BSD distributions do still support i386, i486 or i586 CPUs?
Unfortunately Debian kicked out Pentium 1 (i586) CPU support from its 32-bit PC port (named i386 for historic circumstances) for its next stable release Debian 9 Stretch. (Then again they complain ...
- 985
33
votes
1
answer
3k
views
How does the command.com shell work with MS-DOS?
On my systems that are running MS-DOS, I change the default command.com to 4DOS for more features.
How was the shell system designed and how did it with the operating system in MS-DOS that it enabled ...
- 2,913
22
votes
5
answers
3k
views
Why is the RM Nimbus PC-186 not IBM PC compatible?
The RM Nimbus range of computers were popular in British schools during the late 80s and into the 90s. When I was at high school Nimbus PC-186 machines were all over the place. Many web pages that ...
- 5,271
20
votes
8
answers
2k
views
Retrocomputing software development process/methodologies
This is a test question based on this meta post. If the question can be reworded to be more on-topic, please feel free to suggest improvements. This is an open ended question about software ...
- 9,432
18
votes
1
answer
3k
views
Which undocumented 8085 instructions is Steven Morse referring to in "In The Beginning"?
In S. P. Morse's 1980 allegory, "In The Beginning", he writes
And Intel said, "Let there be an 8085 with an oscillator on the same chip as the processor, and let an on-chip system controller ...
- 3,388
15
votes
2
answers
6k
views
Is the Game Boy Sharp LR35902 object-compatible with the 8080/Z-80?
(Note: by "object-compatible" I mean that the opcodes and their following operands are the same—the assembler produces the same output for equivalant assembler mnemonics. This of course ...
- 24.6k
13
votes
3
answers
2k
views
What format is the (Timex) Sinclair ZX Spectrum SCREEN$/.SCR file
What format is the (Timex) Sinclair ZX Spectrum SCREEN$/.SCR file and how is the fore/background and attribute data encoded within this format?
- 319
148
votes
6
answers
21k
views
Why is the keyboard and cellphone / telephone numbers in a different order?
Cellphone / Telephone have the seven bottom-left and the one top-left.
While the keyboard has the seven top-left and the one bottom-left
How did this come to be? Is there an interesting computing ...
- 6,121
87
votes
9
answers
15k
views
Why is the processor instruction called "move", not "copy"?
Many processors have an instruction called "move" (sometimes spelled MOV) which copies data from one location (the "source") to another (the "destination") in registers and/or memory. It does not do ...
- 2,117
81
votes
10
answers
28k
views
How were the first ZX Spectrum games written?
Being a child of the 80s I loved my ZX Spectrum, did my best to learn BASIC but I felt like the games I was playing (Jetpac, Dizzy, Renegade etc) were perhaps not written using BASIC.
I wondered: how ...
- 1,057
80
votes
14
answers
19k
views
Back in the late 1980s, how was commercial software for 8-bit home computers developed?
When hobbyists wanted to write software for e.g. the Commodore 64, they either used the built-in BASIC interpreter (with all its limitations) or some native tools, like compilers for other languages ...
- 1,502
55
votes
9
answers
25k
views
How long will floppy disks maintain data integrity?
This was on CNN today:
The U.S. is still using floppy disks to run its nuclear program
Which led me to read through this article:
Think the floppy disk is dead? Think again! Here’s why it still ...
- 2,384
55
votes
8
answers
11k
views
Why didn't the 8086 use linear addressing?
The 8086 used a segmented memory architecture where the linear address was computed from a 16-bit segment number and a 16-bit offset. This greatly complicated things from a programming perspective. ...
- 9,290
51
votes
4
answers
4k
views
What precautions to take when powering on old computer for the first time in years
I have a Commodore 128D that hasn't been powered in about 15 years. I want to begin using it again. It has been stored in cool dry places like attached garages, in a cardboard box.
I hope this ...
- 1,055
50
votes
5
answers
17k
views
Why did CPU designers in the 70s prioritize reducing pin count?
A lot of 70s era microprocessors were packaged in DIP packages with 40 pins. This was a reasonably good fit for 8-bit processors: 16 address lines, 8 data lines, 2 power and clock are all absolutely ...
- 12.8k
45
votes
3
answers
4k
views
Why are the symbols on the number keys of PC & Mac keyboards different to ASCII keyboards?
On a US-layout PC keyboard, the symbols above the number keys are as follows:
Whereas the keyboard on an Apple II is different:
Note, for example, the '(' and ')' symbols are now above 8 and 9, and '...
- 8,036
43
votes
4
answers
14k
views
Why did 80x25 become the text monitor standard?
Prior to the 1981 release of the IBM PC, the VT05 (72x20 1970), VT50 (80x12 1974), VT52 (80x24 1975), and VT100 (80x24 1978) text terminals were used on many Unix machines and the PDP-11 (probably the ...
- 1,339
34
votes
9
answers
40k
views
How can you connect an Amiga 500/600/1000/2000 to a modern monitor?
I have an Amiga 500 that I'd like to get up and running again, but the 1084 monitor with which I used to use it has flyback transformer issues.
What options are available to hook it up to a modern ...
- 1,632
28
votes
2
answers
8k
views
The start of x86: Intel 8080 vs Intel 8086?
Why is it said that all modern Intel processors of the x86 family are said to descend from the Intel 8086 and not the Intel 8080? From the Wikipedia article on the Intel 8086,
The 8086 gave rise to ...
- 3,388
22
votes
1
answer
4k
views
How did large .COM files work?
An MS-DOS .com file is just raw code/data without header, thus no linking information, and was limited to be loaded into just one segment (64kB). That's the reason corrupted binaries would print "...
- 1,200
22
votes
3
answers
3k
views
What makes slot 7 of the Apple ][ unique from 1-6 and how was this used?
In the Apple II, there are three unique slots (depending on model):
Slot 0 (on the ][ / ][+) which is typically used for language cards.
"Aux" slots in the //e and IIgs, typically used for memory ...
- 15.8k
20
votes
1
answer
2k
views
Apple IIgs: Hardware implementation of RAM shadowing
On the Apple IIgs, the 256K of built-in main memory is divided into two sections: The "fast" RAM, banks 00 and 01, and the "slow" RAM, banks E0 and E1. CPU access to slow RAM required the CPU to slow ...
- 748
18
votes
1
answer
1k
views
Can you use 5.25 HD floppy disks in a DD drive?
Is is possible to format and use 5.25 high density disks in a double density drive?
- 183
17
votes
3
answers
2k
views
Why does Sinclair BASIC have two formats for storing numbers in the same structure?
The ZX Spectrum has two formats for storing numbers, both 40 bits, or five bytes.
The first is a floating point format, which consists of one exponent byte, and four mantissa bytes. The first bit of ...
- 38.2k
16
votes
3
answers
3k
views
Finding byte boundaries in floppy disk MFM bitstreams
I'm building myself a floppy disk interface based on a microcontroller. I'm successfully reading the bitstream off the disk and (probably) decoding the MFM bitstream into actual bits, based on the ...
- 1,320
16
votes
4
answers
3k
views
Did the Intel 8086/8088 not guarantee the value of SS:SP immediately after RESET?
I'm poking at the Intel 8086/8088 (iAPX 86/88) User's Manual, which states on page 2-29 (PDF page 48), table 2-4, CPU State Following RESET, that the state of the CPU after the RESET pin rising ...
- 5,246
14
votes
1
answer
757
views
Why does Applesoft BASIC get confused by a nonzero value at $0800?
Applesoft BASIC programs start at location $0801 in memory (usually). If you put a nonzero value at address $0800, though, you get an error when you try to run the program:
?SYNTAX ERROR IN 65124
...
- 8,775
14
votes
1
answer
991
views
How were Zuse Z22 Instructions Encoded?
The title says it all:
How to En-/Decode Z22/Z23 Instructions?
(History and Linkage:
The question was raised by Wilson in a comment on my answer to his question "Why are PDP-7-style microprogrammed ...
- 213k
11
votes
3
answers
1k
views
Where can I donate my old Computer Shopper Magazines to make sure they get scanned and shared?
I am sure many of you remember the gigantic Computer Shopper magazines of the 1990's; but Computer Shopper actually dates back to sometime in 1979, and still exists in electronic form today.
In my ...
- 9,795
9
votes
2
answers
913
views
74'181 ALU why would anyone (have) use(d) these wild functions? [closed]
Got myself a bunch of 74LS181, because they were cheap and they have been used in the VAX 11/780. And now I made myself a little tester breadboard where I am trying to figure this out in practice. My ...
- 1,377
7
votes
1
answer
937
views
What's the difference between Kansas City tape standard and CUTS?
A number of a different computer systems use a tape encoding based on either the Kansas City or CUTS standards. There's a very brief overview on Wikipedia, but it's not clear what the difference ...
- 12.8k
4
votes
3
answers
3k
views
Reading both keyboard and joystick with non-KERNAL code on C64
I'm implementing non-KERNAL joystick and keyboard controls for my Commodore 64 game.
I used to use the KERNAL SCNKEY routine earlier to read keyboard and it worked well with my joystick port 2 code. ...
- 495
103
votes
18
answers
25k
views
How was early randomness generated?
Many programs make use of randomness, from BASIC guess-the-number games to encryption key generators. This randomness could have been generated in many, many different ways: hardware, software, ...
- 18.5k