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31
votes
5answers
4k views

Why does the 6502 have the BIT instruction?

The 6502 has a bit instruction which copies two of the bits into the N and V flags, pretends to and the byte with the accumulator, but discards the result and only affects Z. I'm having a hard time ...
20
votes
3answers
2k views

When and what was the first 3D acceleration device ever released?

Plain and simple, we know that consumer level 3D acceleration devices roughly appeared in the middle of the 90s, with brands like Matrox, 3DFX, Nvidia and so on. However, such technology for sure ...
34
votes
3answers
4k views

Why are C64 games inconsistent with which joystick port they use?

The Commodore 64 has two DB-9 joystick ports. If I'm the only person that ever plays games on it, you would assume that you could just leave a joystick plugged into Port 1 and be done with it. However,...
8
votes
2answers
279 views

Texas Instruments SN502

My father is an engineer that worked at TI directly under Jack Kilby in the early 60’s. This chip was given to him by Kilby as a “thank you” for all his hard work. We also have the accompanying build ...
9
votes
4answers
1k views

Compaq Portable vs IBM 5155 Portable PC

In 1983, Compaq introduced its first product, a portable computer weighing 28 pounds; 128-640K RAM, two 5.25" floppy drives, 9" monochrome CRT for $3590. It was extremely successful in the market, and ...
13
votes
2answers
393 views

What is known about the internal workings of the Z80?

There is a wonderful project called Visual6502, and I've used it from time to time to figure things out, like exactly the difference between rti and rts. It is good to see which control lines were ...
23
votes
4answers
4k views

Can my floppy disk still work without a shutter spring?

One of my floppy disks' shutter spring got lost. Now the shutter can't slide normally. Can I still use the floppy disk?
7
votes
2answers
397 views

What was the Macintosh's BOM cost?

Andy Hertzfeld revealed that the CPU for the original $2495 Macintosh cost just $9.00. How much did the rest of the computer cost? Was the markup really greater than Pepsi's markup on sugar? How much ...
6
votes
4answers
424 views

Set screen resolution in DOS-only PC

I replaced a failed CRT display with a LCD panel with a VGA controller board. There is no problem with the display when the PC boots up. However, if I switch the display off then I get an 'Out of ...
12
votes
2answers
2k views

What is the purpose of the yellow wired panels on the IBM 360 Model 20?

I just finished reading a story about an IBM 360 Model 20 rescue, and some of the pictures caught my eye. Specifically this one: Searching online, led me to several more pictures, all with ...
43
votes
5answers
15k views

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?
14
votes
4answers
3k views

Why do the i8080 I/O instructions take a byte-sized operand to determine the port?

I thought the i8080 had 8 16-bit IN ports and 8 16-bit OUT ports. Doesn't that mean the instructions IN d8 ; only index 0-7? OUT d8 can only take 8 possible values? What would it be indexing ...
3
votes
3answers
297 views

Creative uses for serial port? [closed]

I know it's still used for many industrial microcontrollers but that's not what I am asking; I also know that it's quite slow. It's just that I hate seeing an unused port on my desktop pc, while all ...
6
votes
1answer
166 views

Why does the Apple IIgs FPI chip buffer the A14 address signal to the ROM?

In the Apple IIgs computer, the address and data buses of the 65C816 CPU connect directly to the onboard ROM, except for A14, which, according to the schematic, is routed through the FPI ASIC. There's ...
9
votes
1answer
130 views

Patch BBC Master ROM using Sideways RAM?

I have a BBC Master 128 with the standard ROM installed. This includes ADFS v1.50 in slot "D". I want to replace this ADFS in ROM with a patched version, loaded from disk, into Sideways RAM. It is a ...
3
votes
0answers
171 views

Early 1982 PCW article about pseudo random dungeon mapping

I am looking for an article from an issue of Personal Computer World (PCW) from 19821 which related to generating mazes/dungeons using pseudo random seeds, what I think are (now) called procedural ...
9
votes
1answer
324 views

Purpose of using REM when running TR-DOS commands in BASIC

When running TR-DOS commands from within BASIC, it's necessary to prefix the command with RANDOMIZE USR 15619: REM: first. I understand the former command, but not the latter. For example, to load a ...
4
votes
1answer
106 views

How to determine PCB revision of a Sinclair ZX-81

I have a ZX-81 in my collection, but do not know what revision it is. The board text just says "Sinclair ZX81". As far as I know, there were 3 revisions of the ZX-81. What are the landmarks I can ...
8
votes
4answers
1k views

Largest memory peripheral for Sinclair ZX81?

Back in the early to mid 1980s, I vaguely recall seeing an advert in a (I think) UK based computer periodical monthly (Your Computer, or Computer and Video Games), for a memory peripheral that offered ...
48
votes
2answers
7k views

How was the blinking terminal cursor invented?

I was just staring at my blinking terminal cursor: And was wondering where it comes from. Does anybody have some piece of history about the blinking cursor? I couldn't find much online. E.g.: when/...
11
votes
4answers
274 views

Preventing socketed chip corrosion?

I spent a couple hours repairing an Amiga A3000 that wouldn't boot yesterday. The fix was to remove Kickstart ROMs, clean the DIP leads and sockets with contact cleaner, and re-insert. Apparently a ...
8
votes
1answer
402 views

How to use TOSEC?

This is probably a stupid question, but I am struggling to understand how to 'use' TOSEC. For those that are unfamiliar with TOSEC (and assuming I understand it correctly) the project aims to catalog ...
7
votes
1answer
254 views

What are the best file formats for backup & emulation of retro game CDs? And why?

In other words, what are some factual, non-subjective reasons why you might choose (or avoid) a certain file format ? (For example, disk usage, audio accuracy, emulator compatibility, etc). I'm ...
3
votes
1answer
181 views

BASIC09 questions

I only learned of BASIC09 today, and I'm trying to wrap my head around it. The manual talks about it being a compiler, but I'm not sure I see significant differences between its I-code and tokenized ...
12
votes
3answers
4k views

When did game consoles begin including FPUs?

Floating-point coprocessors (FPUs) were an expensive, niche, add-on product for early desktop and home computers. but became commonplace by the mid-1990s, as they began to be included within the most ...
9
votes
2answers
461 views

How to use ISA card in modern PC

(Posted this on HW Rec but got no responses.) Would like to use an ISA expansion card in a modern PC. There are Expensive PCI - ISA adapters (but I cannot find any actually for sale now) USB-ISA ...
32
votes
3answers
6k views

Were any of the books mentioned in this scene from the movie Hackers real?

In this scene from the 1995 movie Hackers, Cereal pulls out several books referred to by different colors of the "technicolor rainbow", including a "green one", "luscious orange", the "Pink Shirt book"...
7
votes
2answers
786 views

Motorola 6845 and bitwise graphics

I'm curious about how graphics were drawn on systems using the Motorola 6845. I understand this was used in the CGA? If so, did the 6845 really work bitwise, was the bitwise graphics entirely separate,...
2
votes
0answers
124 views

Can the quality of a programming language be objectively determined? [closed]

Can there really be an objective way to determine the quality of a programming language or is it all just up to the subjectivity of the programmers when the quality of languages are discussed? Is ...
11
votes
2answers
365 views

Looking for ATARI-ST Graphics Image

I am hoping that someone here collects computer images from days gone by. Many years ago when I used my ATARI-ST I made two drawing I believe I used the art program NEOCHROME, or possibly DEGAS. The ...
5
votes
1answer
250 views

XT IDE causes BASIC not to load properly on IBM 5155

I recently picked up an XT IDE. It works fine for the most part, but when I tried to load BASIC samples from the original IBM DOS 1.1 floppy(I was booting from it), the system hung up, only showing a ...
6
votes
1answer
211 views

Where to find a ROM dump for the Atari ST cartridge 'ACTION'

Back in the day I owned a couple Atari ST, I used a cartridge based program for writing video games. It was called "ACTION" Does anyone remember this program or even better, know where I can get a ROM ...
16
votes
2answers
2k views

Was there ever any real use for a 6800-based Apple 1?

This is kind of a difficult question to phrase since the Apple 1 wasn't really that well adopted of a platform - under 200 of them made and mostly abandoned by the company within 2 years. That being ...
17
votes
2answers
659 views

Fate of mystery Motorola RMS graphics chipset (68486 + 68487)

I recently learned that mid 1980s, Motorola was working on a discrete graphics chipset that would be a great leap forward from its 6847 Video Display Generator and 6845 display controller. It was ...
4
votes
1answer
191 views

Was dynamic type check in Pascal commonplace?

The BESM-6 Pascal compiler I'm experimenting with has a notable difference from Standard Pascal: formal arguments of formal parameters-procedures or functions are not specified, but are checked at ...
3
votes
0answers
139 views

Looking for educational AI game for classic macos

I'm looking to find the name of a (purportedly) educational mac game I purchased from a bookfair handout around 1990-91. The concept was that you would make up the rules to your own board game on a ...
4
votes
0answers
80 views

Backlight inverter failure on TI Travelmate

I picked up a TI Travelmate 4000E for free and it worked perfectly using my AC adapter(genuine TI one from another 4000E). The backlight fires up full brightness for about a second, then dies. ...
5
votes
1answer
352 views

Looking for a MS-DOS cars game

Here are few things I remember, but it was not sufficient for me to find the game on a search engine: The game is top-down game - with no camera angle. It is a car game, with cops and robbers. You ...
7
votes
1answer
246 views

How to get BBC BASIC to TRS-80?

I recently discovered there's BBC BASIC for CP/M machines. Having had my fill of Microsoft Basic, I need to get BBC BASIC onto a disk I can boot on a TRS-80 Model 4P. I have no CP/M disk (or image) ...
5
votes
2answers
233 views

Was Vilnius BASIC cross-platform?

It is well established that Vilnius BASIC runs on PDP-11 compatible machines. For example, the BK-0010 and UKNC had Vilnius BASIC in ROM. Apparently, it was closely modelled after MSX BASIC, which ...
8
votes
1answer
502 views

Origins of the “array like” strings in BASIC

A number of early microcomputer BASICs had 'array like strings' that were unlike MS's system and instead behaved like arrays of char. Substrings were accessed using a syntax like: A$ = B$(1,5) as ...
18
votes
2answers
2k views

Did any early RISC OS precursor run on the BBC Micro?

Acorn famously developed the ARM microprocessor using their existing BBC Micros internally, both to simulate the ARM and to develop for actual ARM using a Tube-connected second processor. Later, ...
6
votes
1answer
160 views

Where to find QICStream software for reading old QIC-150 tape?

I'm trying to restore a backup from an old QIC-150 tape. While I'm able to read the raw data from the tape (using linux), I can't recognize the binary format of the data (the tape is not mine). There ...
44
votes
1answer
6k views

Can anyone identify this unknown 1988 PC card from The Palantir Corporation?

I'm trying to restore order to my junk pile office, and I ran across this card. I am usually pretty good at generally identifying old (PC?) stuff, but this one is outside my experience. I think it ...
7
votes
2answers
547 views

How do I allocate more memory to an app on Sheepshaver running Mac OS 9?

I'm trying to play Taskmaker on Mac OS 9 in Sheepshaver on OSX. Taskmaker tells me that it doesn't have enough memory to run in color. Within technical support it says that I have 512 megabytes total ...
9
votes
1answer
551 views

Why wasn't the Z6 version of the Infocom Z-machine ported to the IIgs?

Infocom ported their Z-machine to nearly every viable platform in the 70s and 80s. Zork runs on around 18 different 8/16 bit platforms using earlier versions of the Z-machine. Why was Z6 the graphical ...
7
votes
1answer
174 views

Are there any PDP-8 assemblers that create linkable object files?

I am currently writing a compiler for the PDP-8. The compiler is going to translate source code into PDP-8 assembly code that calls some runtime routines to perform high-level functions such as ...
2
votes
1answer
532 views

What was the first programming language to have 'printf'?

I'm curious as to which language was the first to literally have a formatted text output procedure called 'printf'. A trivial question, sure, but I was prompted to ask by a recent question on ZSPL. ...
17
votes
1answer
2k views

ZSPL language, anyone heard of it?

While reading the Byte sieve article (Gilbreath 1981), I came across a language I have never heard of, ZSPL. I suspected this was actually a specific version of another language, perhaps PL/1. ...
13
votes
2answers
976 views

What was the design of the Macintosh II's MMU replacement?

I am in the process of repairing a Macintosh II and trying to understand the design rationale behind Apple's MMU replacement part installed in this machine. As you can see in the picture, there is a ...

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