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14
votes
3answers
1k views

The Tandy/TRS-80 Multipack Interface (MPI)

A popular, but, much maligned bus expansion device for the CoCo was the venerable MPI. There were several companies who made bus expasion devices for the CoCo, however, this question is related ...
1
vote
2answers
99 views

What do abnormal sounds or vibrations of a spinning floppy disk inside a floppy drive mean?

I saw this floppy drive sound emulator and this floppy disk sound video and wondered if the sound of a floppy drive or more specifically a the sound of a floppy disk spinning in the drive, could tell ...
10
votes
2answers
994 views

Why did IBM want to keep ICL alive?

According to https://en.wikipedia.org/wiki/International_Computers_Limited International Computers Limited (ICL) was a British computer hardware, computer software and computer services company that ...
1
vote
2answers
261 views

Is it possible to read floppy disks at non-standard rotation speeds (RPM)?

According to this article 3.5-inch floppies rotate 300-600 times per minute (RPM). It is possible to overclock the RPM and will that result in higher transfer speeds? Or is it possible to read a disk ...
20
votes
2answers
3k views

Who invented small string optimization?

In the source code of the 1972 Pascal compiler (a very large OCR-ed PDF), there are declarations of variables and record fields of type ALFA, which are "packed arrays" of 10 characters. ...
0
votes
1answer
86 views

Could visual inspection of the magnetic disk be used to detect the quality (or damages) of a floppy disk?

The magnetic floppy disk is sometimes used as an (infrared) light filter as shown on some pictures below. That led me to think about the actual magnetic disk and if inconsistencies or damaged could be ...
7
votes
8answers
3k views

What was this menu application in DOS?

My father's computer in the early 90s (probably 1991, or at the latest 1992) had a piece of software that acted as an application launcher. I think it was simply called "menu". Its graphics ...
5
votes
1answer
320 views

What was the reason for AmiPro's limitation in displaying two pages together when scrolling?

I have fond memories of using Lotus AmiPro word processor. If it would run on 64-bit Windows, I'd probably still use it today. One of the most infamous bugs in the program was its inability to show ...
22
votes
8answers
3k views

Why did the VIC-20 and C64 have only 22 and 40 columns when the earlier PET had 80 column text?

When I was a kid, the "real" computers in movies looked so cool with that 80-column monochrome green text. My first computer was a VIC-20 and it always felt very "toy-like" to me ...
7
votes
0answers
122 views

How did the PSP firmware 5.03 HEN-C exploit work?

On the historical PSP (PlayStation Portable) console on firmware version 5.03 there used to be a thumbnail-based exploit called HEN-C. It worked (under a race condition I presume since it didn't work ...
30
votes
1answer
2k views

How did the various Soviet ZX Spectrum clones support Cyrillic text?

There may be no one single answer to this question, since the various clones might have done this all in different ways. And of course, some clones do not have the Cyrillic text support at all. I'm ...
4
votes
1answer
317 views

What was an Amiga "X-Drive"?

In computer magazine personal ads from the 1990s, I notice multiple mentions of Amigas "with X-Drive". Searching online, I find no mention of this. (Possibly this is because search engines ...
110
votes
5answers
24k views

How can tilting a N64 cartridge cause such subtle glitches?

When the N64 cartridge is tilted in Super Mario 64, it reliably produces glitches such as this. Mario's limbs disappear, he rotates 90° and sinks into the floor, and the music gets messed up (usually ...
31
votes
2answers
6k views

Why does Windows 1.01 crash at the splash screen?

When Windows 1.01 is started under DOSBox, FreeDOS or one of the later versions of MS-DOS, garbage characters are printed on the screen right after displaying the Microsoft logo. Here’s an example in ...
38
votes
3answers
11k views

Were the dungeons in Legend of Zelda designed to fit together?

As can be seen in the image below, the dungeons of Legend of Zelda fit quite well together. Were they designed to be, or is this just a coincidence? Does this make them easier to store, with the ...
14
votes
2answers
3k views

Why are the magnetic floppy disk drives (FDD) heads not frictionless?

After reading this answer to the question How long can a floppy disk spin before wearing out? ... one could see thru the floppy... Not just badly worn, but the magnetic coating was outright polished ...
13
votes
1answer
212 views

"MOS" - Mini Operating System for PDP-11?

Around 1977 or so, I worked with MOS, a "mini" operating system for the PDP-11. I think it was originally developed at SRI, to support the BBN Packet Radio networking research. It was ...
10
votes
1answer
528 views

Is there any public documentation of the LapLink protocol?

Is the protocol used by the DOS Laplink software publicly documented? I seem to remember there were Linux tools that could use it. I cannot find anything useful on their website.
7
votes
1answer
381 views

What is the TPG file format used in the PlayStation release of Zork I?

I'm looking at the Japanese releases of Infocom games, curious to understand how the engine works. Four games were released for the PC98, one of which added graphics for the rooms (Moonmist). Later, ...
10
votes
2answers
792 views

Can the Nintendo 64 run code directly from ROM?

I've read that the usual way to execute code on the N64 is to use DMA to copy it from ROM into RAM, and then run from RAM. However, it seems that the contents of the ROM are directly visible to the ...
15
votes
8answers
3k views

Cost of PC vs. Amiga 500 in Europe

Based on Commodore sales figures, and other historical claims, the Amiga achieved its peak popularity in 1990-91, with European sales being the leader. By 1990, with the rapid fall in PC clone prices, ...
21
votes
4answers
7k views

Why are the Nintendo 64 memory cards' batteries *soldered* on?

After recently learning that it has a battery inside of it, I unscrewed my Controller Pak (N64 memory card) to put in a new battery. The old one says "98" on it, referring to 1998. So it's ...
56
votes
4answers
13k views

On DOS computers, what would the PARK command do?

In 1994 or so, we had an old computer at my primary school. I remember finding out that it had a park command. From reading its documentation, it said that this command should be executed prior to ...
10
votes
3answers
631 views

Is there a non-paging ITS for the PDP-6 or PDP-10?

In the late 60s, the Incompatible Timesharing System ran on a PDP-6 without any paging hardware (i.e. an MMU in modern terminology). See the Jargon entry for BLT, for example, which states (my ...
4
votes
1answer
483 views

What are these graphical display commands?

I have a Pascal program with a fair amount of inline assembly code in it which demonstrates the capabilities of «Электроника МС 7401» — символьно-графический видеотерминал (Elektronika MS 7401 - ...
9
votes
1answer
3k views

Approximately how many 3.5-inch floppy disks have been produced before manufacturing was stopped? [closed]

3.5-inch floppy disks are not produced anymore, with I think Sony being the last to stop manufacturing in March 2011. Meaning that all floppy disks that exist are currently in circulation and the ...
13
votes
4answers
941 views

What are the differences between the various 36-bit computers from DEC?

I want to ask about the PDP-6 PDP-10 various implementations KA-10, KI-10, KL-10 DECSYSTEM-20 What are the differences between these? I'm not that interested in architectural differences, cache ...
9
votes
2answers
292 views

What environment was Coherent developed with?

Coherent was a Unix clone for IBM compatibles Mark Williams Company produced and sold in the 1980s and early 1990s. What environment and tools was Coherent developed with? Was it cross-developed on ...
2
votes
1answer
269 views

When was fixed page size, flexible assignment bank switching patented?

The 8-bit microprocessors invented in the seventies, had a 16-bit address space. It didn't take long for memory demand to exceed this, with the result that bank switching was a fact of life for the ...
26
votes
8answers
3k views

How did debugging software run without memory protection?

Debuggers are carefully written programs that peek and poke other programs while they run. In retrocomputers, programs could use any part of the memory they could access. So how did debuggers insert ...
20
votes
5answers
3k views

How did old computers address far more than 64K of memory despite only having a 16 bit address bus?

I have an old Sharp PC-G830 pocket computer from the '80s that has 32K of RAM and 256K of ROM. I also have a simple single board computer I built with 128K of RAM and a few megabytes of ROM from a ...
17
votes
5answers
2k views

How does a floppy drive identify the first and last sectors and tracks?

I've recently found a more modern application "Floppy Disk Master-7"(Picture 2) (FDM) that visualized the bad sectors, tracks and clusters(Picture 1) on a floppy disk in a similar (but ...
10
votes
2answers
648 views

How does the OPL2 Composite Sine Mode work?

The Yamaha YM3812 (aka OPL2) has an operation mode named composite sine mode (CSM), apparently designed for speech synthesis. Unfortunately I was unabled to find any documentation on what ...
5
votes
4answers
398 views

How did the Spectrum clones with TR-DOS and paged memory load and run code files from disk?

I've been playing with Spectrum emulators, their file formats and some reverse engineering tools recently. Thanks to this forum, I was able to parse the TR-DOS disk image format and find the bytes of ...
5
votes
1answer
188 views

Z80 CPU and nested/reentrant NMI

According to multiple documentation sources, non-maskable interrupts (NMIs) can be nested (or reentrant) in a Z80 microprocessor. This is, upon a /NMI signal pulse, the CPU will interrupt the current ...
4
votes
1answer
419 views

Why did this joke man page use July 16, 1974 as an epoch?

This fake manual page posted to the comp.humor newsgroup jokes that A.out accepts any option passed to it, stalls for a few seconds, and then prints a cryptic message chosen from the list below. The ...
13
votes
5answers
2k views

Magnetic tapes as a random access medium?

A two-part question: How widespread in legacy systems was the practice of using magnetic tapes as a genuinely random access medium at the OS level by pre-formatting them in a way before the first use,...
22
votes
2answers
4k views

How did the ZX80 store both a useful program and screen memory?

I have a vague recollection from my earliest days that the ZX80 only shipped with 1K of RAM. If this RAM was used to store both the program and the contents of the 32x24 screen, wouldn't that mean ...
14
votes
1answer
1k views

l-------l.com, a weird web page from 2000

I remember a mysterious web page from 2000 with the domain name l-------l.com. This domain name goes against RFC 5891 but it was valid back in the day. It's pretty hard to search for this. Most search ...
4
votes
1answer
199 views

What information could be recovered from visualized magnetic information?

I was wondering how the data on a floppy disk physically looks like. With data stored on a magnetic disk obviously that isn't visible. The Wikipedia article on floppy disks however shows a beautiful ...
27
votes
2answers
7k views

Why did Nintendo name its console the "Famicom"?

The NES was known as the "Famicom" in Japan, short for "Family Computer". But why was it given an English name in Japan, given (I assume) most people wouldn't know what the words &...
10
votes
3answers
2k views

How good is this random number algorithm?

What follows are the random number generation routines from an ALGOL-60 computational math library, stored on a BESM-6 disk in a text form. The character encoding was with parity, imitating a punched ...
10
votes
1answer
366 views

1990s BBS game featuring mining elements from a planet

Sometime in the 90s (sorry, can't be more specific) I used to dial in to a BBS and play a multi-player game that involved manually mining elements from a planet. It was very detailed, you got employed ...
13
votes
14answers
2k views

Emulators running on 8-bit personal computers

Were there emulators running on 8-bit computers (preferably "mainstream" personal ones), available to general public (as opposed to in-house developers only)? I am mostly after emulators ...
3
votes
1answer
83 views

What disk packs are compatible with the DEC RM05?

While the majority of DEC's PDP-11 systems used UNIBUS or QBUS based peripherals for storage, some of the larger PDP-11s, along with larger machines such as the DECsystem 20 and the VAX-11/780 used ...
16
votes
1answer
1k views

What did memory dumps look like on 36-bit machines like PDP-10s?

I spend a lot of time looking at hex dumps of memory, which have a format that should be familiar to most: 00010000 00 FF 48 65 6c 6c 6f 20-77 6f 72 6c 64 21 00 00 ..Hello world!.. But on 36-bit ...
10
votes
2answers
323 views

Which plotter used these commands?

I've found a BESM-6 binary of a Pascal program which plots pretty pseudo-random pictures, like this A date is given as the seed for the RNG, in a "horoscope"-like fashion. After decompiling,...
3
votes
4answers
556 views

Where can I find a 26-pin flex flat cable for the floppy drive in a Toshiba T19x0 laptop?

I was trying to take apart a Toshiba T1950ct laptop to replace the slim floppy drive’s belt. Unfortunately, I broke the delicate flat flex cable (ffc), which is a non-standard 26-wire floppy cable. ...
7
votes
4answers
816 views

What was the first PC/computer to have sound recording & playback support?

Sound playback and recording became mainstream on computers today, the most known introduction was around 1989-1991 with the release of windows 3.0 with Multimedia Extensions. However, what was the ...
48
votes
6answers
7k views

What is a Dumb Terminal?

There seems to be some confusion what a 'Dumb' terminal is as visible in answers and comments to this question about portable dumb terminals. So: What is a Dumb Terminal? Points that would help to ...

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