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votes
10answers
11k 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 ...
57
votes
3answers
6k 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 ...
45
votes
4answers
32k 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 ...
23
votes
4answers
5k 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 ...
34
votes
3answers
8k 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 ...
33
votes
3answers
3k 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 ...
84
votes
8answers
31k 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 ...
25
votes
4answers
10k 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 ...
19
votes
7answers
1k 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 ...
16
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5answers
2k 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", ...
7
votes
4answers
6k 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 ...
71
votes
9answers
22k 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 ...
55
votes
5answers
14k 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 ...
57
votes
3answers
13k 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 ...
48
votes
4answers
3k 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 ...
48
votes
8answers
16k 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 ...
42
votes
3answers
3k 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 '...
26
votes
2answers
3k 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 ...
3
votes
3answers
2k 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. ...
22
votes
3answers
2k 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 ...
10
votes
3answers
1k 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?
46
votes
8answers
9k 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. ...
44
votes
2answers
10k views

How did the Z80 instruction set differ from the 8080?

The Zilog Z80 microprocessor, known for its use in the ZX Spectrum, was designed to be a backwards-compatible extension to the Intel 8080 processor. It introduced several new instructions to the 8080'...
62
votes
5answers
14k views

Is it safe to turn on a 40-year old TRS-80?

My father is a retired programmer. When I was in high school in the late 1970s, he purchased a TRS-80 model 1 (on which I learned to program in BASIC). At some point in the early 1980s it, together ...
92
votes
6answers
9k views

Were there 8086 coprocessors other than the 8087?

The 8087 math coprocessor for the 8086 (and descendants) nominally added floating point and transcendental (trigonometric and logarithmic) instructions to the 8086. Contrary to naive expectations, the ...
21
votes
3answers
5k views

Wiring a Zilog Z80

I've recently got hold of an old Zilog Z80 microprocessor and I know how to clock and test it. I do not however know how to connect RAM, I/O ports, control switches (for programming instructions into ...
21
votes
2answers
5k 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 descent from the Intel 8086 and not the Intel 8080? From the Wikipedia article on the Intel 8086, The 8086 gave rise to ...
46
votes
7answers
10k 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?
43
votes
5answers
16k 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 ...
42
votes
7answers
5k views

Why does the Commodore C128 perform poorly when running CP/M?

I have seen several claims of poor performance of the C128 when running CP/M, and would like to better understand these claims, especially in comparison to other CP/M machines of the early to mid-...
29
votes
1answer
3k views

What is the relative code density of 8-bit microprocessors?

When RAM is at a premium, as it was in the old days, a greater code density of an instruction set can be a substantial advantage. (Click saver: Code density refers loosely to how many microprocessor ...
30
votes
5answers
3k views

Does every retrocomputer and console with NTSC composite output have 'artifact color' ability?

Artifact color is heavily associated with the Apple ][, since that is the only method the machine had to produce a color display. I was looking at the fantastic demo for IBM PC + CGA, 8088MPH, and I ...
28
votes
6answers
16k 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 ...
28
votes
8answers
9k views

NES cartridge ROM emulation with Arduino or Pi?

I'm looking to buy or make an NES cartridge that can be controlled by a microcontroller or small computer like the Raspberry Pi. I don't want to gut an NES cart and put an NES emulator inside it (as ...
17
votes
1answer
2k 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 ...
23
votes
4answers
5k views

Why did Pokémon Red have so many overflow bugs?

(This question also applies to other Game Boy games, but Pokémon seems to be one of the best-documented.) Pokémon Red & Blue (Red & Green in Japan) is a pair of Game Boy games about capturing ...
15
votes
4answers
2k 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 ...
30
votes
4answers
8k views

History of Ctrl-S and Ctrl-Q for flow control

Which OS was the first to use Ctrl-S and Ctrl-Q on the console for pause and continue? I first discovered Ctrl-S in IBM PC DOS 1.1.
10
votes
2answers
2k views

How does the 6502 implement its branch instructions?

The 6502's decode ROM takes an input which tells it when to start the next instruction. In the case of something like an INX or LDA #7F, it is obvious that once the output from the ALU has been ...
21
votes
1answer
1k views

When does the VIC-II read the sprite data?

This question is about the Commodore 64 and its graphics chip, the VIC-II. Imagine that on a particular scanline, the VIC-II needs to fetch 40 bytes (the background tiles) and since it's a badline ...
19
votes
1answer
1k 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 ...
19
votes
4answers
3k views

How did integer multiplication work in 8-bit BASIC without CPU support

I've recently been teaching my 11 year old binary multiplication, which is on the UK maths syllabus at secondary school. We have used long multiplication, eg shift and add. This has made me wonder ...
18
votes
2answers
5k views

First commercial DOS game?

What was the first commercial game sold for use on IBM/MS/PC DOS after the IBM August 12, 1981 release.
16
votes
3answers
2k views

How did the IBM PC handle multiple physical devices serving memory at the same physical address?

I'm trying to figure out how the IBM 5150 PC handled the case where multiple physical devices (memory chips) were mapped to the same address within the 8088's physical address space. The closest I've ...
16
votes
1answer
1k views

What's the timeline of Motorola 6800-family CPUs from 1974 to 1979?

According to Wikipedia, The Motorola 6800 was released in 1974. Between that and the release of the 6809 in 1979 (or 1978?) there was at least one other 6800-series CPU released, the 6802 ...
13
votes
4answers
2k views

Make a BASIC TAP file readable on Linux

I am trying to convert my own BASIC TAP files (containing BASIC programs) to text so that they are readable on my Debian GNU/Linux machine. If I open them as is, I get this, which gives me some hope, ...
13
votes
1answer
460 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 ...
6
votes
1answer
406 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 ...
0
votes
3answers
344 views

The earliest a home-computer or home-robot could be interfaced with a commercially available camera?

What was the earliest date a home-computer or home-robot could be interfaced with a commercially available tv-camera or digital-camera . Although I'm asking this question for the purpose of computer-...
126
votes
4answers
34k 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 ...

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