Questions tagged [hardware]

Retro hardware generally: boards, extension cards, power supplies, peripherals. Use more specific tags as appropriate; use [case] instead for enclosures.

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138 votes
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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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97 votes
17 answers
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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, ...
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90 votes
20 answers
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Have programming languages driven hardware development?

Programming language development has been influenced by hardware design. One example from this answer mentions how C pointers were, at least in part, influenced by the design of the PDP-11. Has the ...
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63 votes
5 answers
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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 ...
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60 votes
13 answers
12k views

How big is a mainframe?

If you read about the history of computing, you'll hear how the first computers were "huge". You will often come across assertions that in the early days of commercial computing, a single computer ...
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60 votes
6 answers
9k views

Reason for the Amiga clock speed

The Amiga used a CPU rated for 8 megahertz, but clocked at 7.14 megahertz. What was the reason for this number? I remember it was something to do with a multiple of the frequency of the video ...
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59 votes
6 answers
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What did the 'turbo' button actually do?

I remember the computer I played Commander Keen on as a child had a turbo button that I was forbidden to touch, what did this button actually do?
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54 votes
11 answers
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Why did trackballs disappear?

For a desktop computer, a mouse is a great pointing device. For a laptop if you don't want an extra device to keep track of, you need an alternative. The options I'm aware of: NubLow-tech, cheap, ...
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53 votes
17 answers
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Simplest system to create an emulator for

Next year I'm going to teach a 2-semester microprocessors class to third-year undergraduate EE students. In order to sign up for the class, students need to have completed programming and digital ...
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51 votes
4 answers
6k views

Why did the IBM 650 use bi-quinary?

The IBM 650, announced in 1953, was the world's first mass-produced computer. It represented numbers in decimal, which is understandable, both because it needed to work with exact money amounts, and ...
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48 votes
2 answers
11k views

Why does the 80486 take longer to execute simple instructions than complex ones?

The 80486 processor can execute many instructions in a single cycle, such as a register-to-register add instruction (ADD EAX, EBX, for example), which one would generally assume is fairly complex, ...
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48 votes
6 answers
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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 ...
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47 votes
8 answers
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Why were chips socketed in early computers?

In many early computers, many of the chips were in sockets rather than soldered directly to boards, e.g. this series of pictures of the Tandy CoCo 1 has a note to the effect that all the chips are ...
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42 votes
3 answers
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Was AGP only ever used for graphics cards?

Reading on the AGP spec, the little bits I've found on sites like https://old.pinouts.ru/Slots/agp_pinout.shtml, say: The Accelerated Graphics Port (also called Advanced Graphics Port) is a high-...
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40 votes
4 answers
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What determines the color of every 8th pixel on the Apple II?

On the Apple II there's an interesting way to add a little color to the bitmap, since the high bit select the palette used for the three-and-a-half pixels represented by the byte. Like this: 0: Black,...
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39 votes
5 answers
6k views

Why do programmable sound generators like SID include a noise generator?

In layman's terms, please explain the reason that all the popular PSG's used in 1980s computers and game consoles provided an additional channel to generate programmable "noise". How was this "noise" ...
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39 votes
4 answers
8k views

When did computers stop checking memory on boot?

I remember my old 8088 used to do this (640K OK) but can't remember seeing anything like this since. Does this still happen and it's just not visible? If not, when did it stop, and why? (Imagining ...
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38 votes
6 answers
10k views

Why did early arcade games use vertical displays?

Surprisingly many early arcade games, such as Pac-Man, Galaxian and Galaga, mounted their displays vertically, in portrait rather than landscape orientation. (From the perspective of the electronics, ...
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38 votes
4 answers
6k views

Why did so many early microcomputers use the MOS 6502 and variants?

Quite a few successful early microcomputers used the MOS 6502 CPU. This included, but was not limited to, systems like the Apple I, Apple II, Commodore PET, and Ataris. A followup known as the MOS ...
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38 votes
3 answers
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Why did the VIC-II and SID use 6 µm technology in the era of 3 µm and 1.5 µm?

In short, 3 µm looks like it was the "standard" process size at the time, and it was available to Commodore before the chips were designed. Therefore it looks like using the larger 5 to 7 µm process ...
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35 votes
6 answers
9k views

Using DRAM as a camera sensor?

Back in the days when COMECON (RVHP) was cloning digital ICs usually the first wave of such ICs were in a ceramic package with a glass window (similar to EPROM) to check for bugs and stuff while used. ...
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34 votes
6 answers
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Why do hard drives not use larger platter sizes anymore?

In reading a related question about floppy drive capacity, I thought to ask a question I've had for a long time. When I started programming, all PC hard drives used the 5¼" platter size. There were ...
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34 votes
5 answers
4k views

Which ports are which on this Soviet ZX Spectrum clone?

Today I got my (first) Soviet ZX Spectrum clone. The person who sold it to me had inherited it and had no idea how it worked. It seems to be a home-made clone, rather than a factory-built one. See ...
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33 votes
4 answers
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Why was manual branch suggestion abandoned?

Once pipelined CPUs became common, a common issue arrived as a result of taking the wrong branch of a conditional jump, and thus needing to flush the pipeline. As a result branch prediction mechanisms ...
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32 votes
17 answers
12k views

Was there a retro computer susceptible of being damaged only by issuing instructions at it?

The question 'Can a USR command damage a ZX Spectrum?' has led me to wonder if there was once a microcomputer that could actually be damaged by software. More specifically: Is there a case that a ...
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32 votes
6 answers
6k views

Why did Commodore sell CPUs to its competitors?

Many of the most popular personal computers and video game consoles of the 1970s and 1980s, including those made by Commodore, Apple, and Atari, used the 6502 CPU (or some close relative, such as the ...
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31 votes
10 answers
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Should 486s have a heatsink?

I'm building a 486 computer. I plan on using a 100 MHz 486-DX4 that I have which I believe is about as fast as 486's went. The motherboard I will use (Socket 3) appears to support putting a heatsink ...
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31 votes
1 answer
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What are the Amiga 1200 timing fixes?

I have read that the Amiga 1200 may need certain "timing fixes" to be applied to the motherboard in order to use CPU accelerators. What are these timing fixes and why are they needed? Is there one ...
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29 votes
9 answers
11k views

How did early x86 BIOS programmers manage to program full blown TUIs given very few bytes of ROM/EPROM?

I've always wondered how so much functionality and relative luxuries(CMOS Configuration Utilities. See: https://geekprank.com/bios/ for an example) included with most popular x86 BIOSes could be ...
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29 votes
3 answers
6k views

386SX, NES and how much did data lines really cost anyway?

In 1988, Intel introduced the 80386SX, most often referred to as the 386SX, a cut-down version of the 80386 with a 16-bit data bus mainly intended for lower-cost PCs aimed at the home, educational, ...
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29 votes
5 answers
5k views

How did the BBC Micro stay cool?

The BBC Micro used the extended variant of the classic 'computer in keyboard' design; like the Apple II, the case went back far enough that you were encouraged to put the monitor on top of it. All ...
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29 votes
3 answers
5k views

Why did the ZX80 CPU run at only 3.25 MHz?

The Sinclair ZX80 used a Z80A running at 3.25 MHz. But this chip was rated for 4 MHz. Why was it run below rated speed? Apparently the master clock in the machine ran at 6.5 MHz, so the CPU clock ran ...
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29 votes
3 answers
3k views

What are the differences between a PAL and NTSC C64?

A lot of programs released for the Commodore 64 contained different software for the PAL or NTSC computer. Why did they have different versions of the hardware? Did the software have to be different ...
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29 votes
1 answer
2k views

How do Amiga 600 CPU accelerators work?

The Amiga 1200 has a trapdoor expansion for CPU accelerators. The Amiga 500 has a side expansion port and its CPU is socketed. But Amiga 600's expansion port is only useful for memory expansion ...
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29 votes
1 answer
5k views

How can I take an image of a 50-pin SCSI hard-drive

I have two 50-pin SCSI hard-drives that I need to image. However, after spending quite a while searching across the Internet, I cannot find any adapters to convert the 50-pin connector to something ...
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28 votes
25 answers
4k views

Which computers had redefinable character sets?

My first computer was an Exidy Sorcerer, bought in the late '70s. It featured a full keyboard including lower case, on screen text of 64 B&W characters by 30 rows, 2 MHz z-80 processor, up to 48 ...
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28 votes
7 answers
12k views

Why did computers use a power supply with a socket?

Most home electrical appliances use a fixed power cord and have a on/off switch near the front. I was in many government electronics labs and that cord and socket was not used i.e HP test equipment. ...
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28 votes
3 answers
21k views

Why do Game Boy Colors not want nickel-cadmium batteries?

This is a page from the manual for the Game Boy Color: There is no explanation as to why this is, or how this can be, but it claims that one must not use rechargeable nickel-cadmium batteries. Why is ...
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28 votes
2 answers
3k views

Why did connecting the IBM PC 3.5" FDD backwards cause the problems it did?

When the 3.5" FDD was introduced for the IBM PC and compatibles (or possibly earlier), someone made a decision to make the data cable between the controller and drive unkeyed. This, of course, meant ...
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28 votes
2 answers
4k views

How does the NES Light Gun work?

Modern motion detection video game systems (Wii/Wii U, Xbox Kinect, PS Move, etc.) need sensors to read for motion and user input. However, when you play Duck Hunt (and some other games) on the NES, ...
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27 votes
2 answers
6k views

How did the "Programmer's Switch" work on early Macintosh Computers?

The early Apple Macintosh computers (original Mac, Mac 512K, Mac Plus) all came with a "Programmer's Switch" installed on the side. I believe this persisted for a long time, with the switch ...
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27 votes
3 answers
7k views

In what ways was the Soviet Strela computer "designed to function during a nuclear winter"? Or at least parts of it?

From Strela computer: Strela computer (Russian: ЭВМ Стрела, arrow) was the first mainframe computer manufactured serially in the Soviet Union, beginning in 1953. This first-generation computer had ...
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26 votes
10 answers
7k views

Graphics chips in 1980

Suppose you were trying to build a computer with a color graphics display in 1980, you have limited engineering resources and time to market is critical, so you want to get as many of the parts off ...
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26 votes
6 answers
7k views

Why weren't discrete x86 CPUs ever used in game hardware?

Please don't point out APUs with x86_64 cores used in current generation game consoles, these are not part of the question I cannot recall a single arcade system or game console that ever used x86 ...
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26 votes
4 answers
4k views

What register size did early computers use?

Prompted by this question querying the prevalence of byte-addressable memory on machines with 32 bit registers: Why is every address in a micro-controller only 8 bits in size? I'm familiar with the ...
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26 votes
3 answers
4k views

When did 5.25″ floppies exceed the capacity of 8″?

When 5.25″ floppies were introduced, in the mid-to-late seventies, they would have had less capacity than the older 8″ because, well, less area on which to store data. On the other hand, being cheaper ...
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26 votes
4 answers
3k views

When you type on a computer terminal, how are the characters displayed on the screen?

Assume that the following computer terminal is connected to a large computer: When I type something on the keyboard (for example: pwd), is it the computer terminal the one that receives the ...
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  • 1,807
26 votes
5 answers
5k views

DIY Project using 1970s 8-bit CPU, is it possible?

I've recently really wanted to try and design a computer system around a retro 8-bit CPU such as the Zilog Z80 or the Intel 8080, and I would appreciate some sanity checks! I was inspired by Ben Eater'...
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  • 363
25 votes
7 answers
10k views

Did any computer use a 7-bit byte?

In an answer to Why did IBM System 360 have byte addressable RAM I wrote regarding the choice of byte size: 7 bits would be a perfect match for ASCII, but engineers would instinctively recoil from ...
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25 votes
7 answers
7k views

Purpose of turbo switch on systems unable to slow to 4.77 MHz?

I have a PC with an Intel P133 (133 MHz). The motherboard (PcPartner MB520NH) only allows for it to be slowed down to 75 MHz at the least via jumper settings, but no lower. Yet the PC's case has ...
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