All Questions

10
votes
3answers
338 views

Who invented scrollable screens in Amiga?

A well known feature of Amiga is the ability to have multiple Intuition screens (ViewPorts in graphics.library parlance) that coexist and can be laid out on the screen so that they overlap vertically. ...
21
votes
3answers
4k views

Why did the ZX Spectrum use an internal speaker?

I was surprised to note recently that the Sinclair ZX Spectrum used an internal speaker. I knew the BBC Micro used one, presumably because it was designed to be optionally used with a monitor which ...
4
votes
2answers
298 views

How to convert .ttf to .fnt for use with M10_SCR.COM DOS font driver

I have a DOS program M10_SCR.COM that loads as a TSR and allows the use of fonts. It works with its own basic built-in fonts, so now I am trying to convert .ttf fonts into .fnt so I have more fonts to ...
3
votes
3answers
245 views

3 decimal digits per 10 bits

Early computers often had hardware support for decimal arithmetic. This was usually in the form of BCD, 1 decimal digit per 4 bits, e.g. the 6502 and Z80, tightly constrained by transistor count as ...
7
votes
2answers
409 views

Why is the BBC Micro's Mode 7 so different to the other display Modes?

Mode 7 on the BBC Micro is very different to the other seven display Modes (0-6). From the programmer's point of view, the BBC Micro's mode 7 looks like 'oh, there is also a character cell mode that ...
3
votes
1answer
96 views

Sam Coupé power supply heat

I have a Sam Coupé and the last time I turn it on, i noticed a smell of components overheating. After opening the power supply I came to the conclusion that is the resistance R1 (50ºc with IR ...
29
votes
2answers
3k views

Why did the C64 have ← and ↑ as dedicated keys?

I've always wondered why the Commmodore 64 had discrete keys dedicated for the ← and ↑ symbols. If I remember correctly, they weren't used in BASIC at all, and were not very useful for drawing, ...
9
votes
4answers
953 views

UCSD P-System: Why only 77 files per volume?

What was the reason that the UCSD P-system filesystem was designed in such a way that it was limited to 77 files per volume?
2
votes
5answers
495 views

Was it possible to send data over the phone-line without a modem?

Was it possible to send data over the phone-line without a modem? Clarification Was it possible to send data over the phone-line without a modem, either by connecting computers directly to the ...
5
votes
1answer
156 views

Would a replacement screen from a TRS-80 model 102 work for a model 100?

A few weeks earlier I have purchased an "as is" but working model 100 laptop. I've fixed some of the issues by soldering new capacitors for the screen, but the lines are still there. Would buying a ...
10
votes
1answer
642 views

Examples of operating systems using hardware task switching of x86 CPUs

Intel IA-32 architecture a.k.a. x86 offers hardware task switching capabilities since 80386. It includes TR (task register), memory segmentation features such as Task State Segment, task gates, call ...
33
votes
1answer
3k views

How did the 8086 interface with the 8087 FPU coprocessor?

The 8087 has many instructions - too many, it seems, to be encoded as part of the 8086 instruction set. How did the Intel 8086 interface with an Intel 8087 FPU that a user added? Consider the ...
1
vote
1answer
101 views

Capacitor replacement on European 220 volt Mac 512K And Plus

I have had two Macs, a 512K and a Plus, in storage since they failed the smoke test in a spectacular manner a few years back. I have finally learned how to solder and de-solder, so I think its time to ...
2
votes
1answer
217 views

How to repair an old motherboard

I recently got some old motherboards. I was able to fix a damage caused by a leaked battery on a 486 board by soldering a bypass (to fix not working keyboard plug). Another board is in a good shape ...
10
votes
2answers
271 views

What is the minimum set of Kickstart kernel modules to allow an Amiga to boot?

Amiga OS resident modules (libraries, devices, etc...) are location-agnostic, in that it is technically possible to compile them as location-independent code to be loaded at runtime from disk, or to ...
5
votes
1answer
249 views

Were there any working computers using residue number systems?

Wikipedia says: A residue numeral system (RNS) is a numeral system representing integers by their values modulo several pairwise coprime integers called the moduli. Bit widths of each of those "...
4
votes
3answers
257 views

Comparing Signed Numbers on Z80 (8080) in Assembly

How do you compare two signed numbers in Z80 assembly? According to this site, To compare stuff, simply do a CP, and if the zero flag is set [then] the argument[s] were equal, else if the carry ...
3
votes
2answers
292 views

Did any early computers use a different radix to improve accuracy of rational arithmetic?

Fractions like a third, a fifth, a tenth and so on cannot be precisely represented in binary, because those would be recurring fractions and so would never fit in a (reasonable) data structure. And ...
2
votes
3answers
193 views

What was the DOS FAT12 720k floppy raw disk format structure?

I am looking for detailed info on the low-level floppy disk structure of an MSDOS-compatible 720k Double Sided Double Density disk. Stuff like GAP/SYNC patterns, ID and CRC Field structure, standard ...
11
votes
5answers
3k views

What was the first games console to support linking consoles together for local multiplayer?

Most video game consoles allow you to connect multiple controllers to them, for multiplayer gaming. Handheld game consoles, on the other hand, were designed to be used by one person at a time, but ...
2
votes
3answers
268 views

What characters which were in use at the time were excluded from ASCII?

The American Standard Code for Information Interchange is a 7-bit character encoding. Work on the standard began in 1960 and the first edition was published in 1963. The standard attempted to ...
2
votes
1answer
177 views

Commodore PC-1 power supply measurements off

I have a Commodore PC-1 with a busted power supply. I have no desire to fix it as I don't have the know-how it is already 30 years old It is difficult to debug / find replacement components So I ...
6
votes
1answer
309 views

Common practices of programming the AY-3-8910 on Amstrad CPC: via Firmware routines or directly?

I'm starting to learn how to program in assembly (z80) on the Amstrad CPC computer. As an high level developper i find it pretty fun and i learn a lot of things about computer and CPU architecture. ...
30
votes
2answers
2k 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 '...
2
votes
2answers
107 views

AppleTalk adapters to bridge LocalTalk to Ethernet?

What AppleTalk adapters can bridge LocalTalk to Ethernet? There are some adapter that allow LocalTalk printers to show up on ethernet, but I want to allow computers to talk. My IIgs has LocalTalk but ...
1
vote
0answers
85 views

Cannot get K prompt on Timex 1500

I started tinkering with a Timex Sinclair 1500 I was given awhile ago. When I first tried starting it, I got a K prompt in the lower left of the screen. I turned it off and did not return to it for a ...
17
votes
4answers
5k views

What was the effect of the Video Game Crash of 1983 outside of North America?

The Video Game Crash of 1983 is well known for the effect that it had on the video game console market in North America. A prime example is Atari burying thousands of unsold game cartridges in ...
4
votes
1answer
179 views

Why does my Epson HX-20 apparently have much less RAM than expected?

When I enter: STAT ALL On my Epson HX-20, I get the following output: P1: 419 Bytes P2: 86 Bytes P3: 0 Bytes P4: 0 Bytes P5: 0 Bytes RAM FILE 256 Bytes MEMSET 2624 105 Bytes Free As I ...
12
votes
3answers
2k views

What was the first microprocessor to support full virtualization?

Virtual memory, which allows an operating system to run several machine code programs isolated from each other, came to the desktop during the eighties. But full virtualization, which lets the ...
12
votes
10answers
2k views

Which microcomputer manufacturers developed their own Local Area Network systems? [closed]

With the advent of microcomputers, there was a large number of manufacturers entering the home computer market. The ability to network these computers together wouldn't be very useful (or affordable) ...
3
votes
1answer
163 views

How was dataflow analysis performed before SSA?

If we look at something like LLVM or the GNU Compiler Collection, Dalvik and many others, their intermediate representation (IR) uses SSA (Static Single Assignment form), as part of their Data-Flow ...
30
votes
6answers
10k views

Which was the first programming language that had data types?

Machine language (and Assembly language) don't have the concept of data types, so if you want to add an int and a float variables in Assembly, you have to use the appropriate Assembly instruction that ...
19
votes
5answers
7k views

Will PC-DOS run faster on 4 or 8 core modern machines?

When I run PC-DOS on my 4 core AMD Phenom chip, does it take advantage of the extra parallel CPU's? If not, is there a way to coax DOS to use all available CPU's or does this require specific ...
10
votes
3answers
2k views

What was the largest resolution supported by terminal escape codes?

Terminal escape codes can be used for various functions such as positioning the cursor or querying the size of the screen. What was the largest resolution (in columns and rows of characters) ...
4
votes
1answer
255 views

Is is possible to repair a SE/30 with reversed C2 and C11 capacitors?

Shamelessly stolen from BobDenford on Reddit. I recapped my SE/30 but mistakenly reversed the polarity of the two axial capacitors (C2 and C11). Prior to my error, the machine was fully functional ...
9
votes
3answers
244 views

How can a peripheral work on both the ZX81 and on the ZX Spectrum?

The ZX Printer was made to work with both the ZX81 and the Spectrum (or rather, the Spectrum was made to work with the ZX81's printer!), but these computers have different expansion ports. What I ...
3
votes
1answer
150 views

First Commodore 80-column monitor

While the Amiga could be used with a TV in a pinch, it was primarily intended for use with an RGBA monitor; memory says, and Google seems to confirm, that was the 1084. Commodore made color monitors ...
6
votes
3answers
849 views

Was there a Western computer with blatantly missing instructions in the instruction set?

In the BESM-6, there is an instruction (045) to add index registers, but not to subtract them, however, there is a nearby unused opcode 047, which is made synonymous to 045 (in fairness, that's true ...
5
votes
3answers
158 views

How does the floating point conversion in Zuse's machines work?

Can someone please help me understand the floating point to readable decimal conversion algorithms of the Z1 and Z3? There is a patent in German containing all the information but I can't speak German....
4
votes
1answer
187 views

ENIAC stands for Electrical Numerical Integrator And Calculator; what made it particularly suitable for numerical integration?

The acronym ENIAC stands for Electrical Numerical Integrator And Calculator. The fact that it was simpy a numerical computer means it probably could be used to perform numerical integration in some ...
5
votes
2answers
201 views

In what way could the Sperry Univac BC-7 computer “speak and understand” English?

Researching for this question I ran across this 1978 advertisement for Sperry: Sperry Computer Ad 1978: https://www.youtube.com/watch?v=I74sVdw7gkc The computer is nicknamed "B.C." and the actor ...
5
votes
2answers
311 views

Where was this Grace Hopper/Univac photo taken?

Here is a photo of a Univac I with four individuals. According to Artifact Details at the Computer History Museum's web page with an extremely similar photo (perhaps a shot a few moments earlier/later)...
4
votes
2answers
149 views

Single-stepping the Altair 8800

I've just been watching a rather interesting series of videos about the MITS Altair 8800. It has a button on the front panel to single-step the CPU one instruction at a time... Except that, on closer ...
2
votes
3answers
279 views

History of advanced hardware [closed]

Like most people, I grew up in the 1980s, and bore whitness to the great 8-bit home computer revolution. From where I'm sitting, "computers" started with slow 8-bit machines just powerful enough to ...
8
votes
5answers
3k views

What was the main purpose of bitshift instructions in CPU?

As far as I know, even simple RISC microcontroller have a bitshift operator, and honestly I had to use it only once when I had to compute a division on a MCU that could not do divisions in the ALU. ...
3
votes
2answers
356 views

TCP over RS-232 with Windows 3.1 and Internet Explorer 5 dialer

I am restoring a Windows 3.1 computer that has Internet Explorer 5 installed. I would like to connect it to the internet using a Linux-based laptop as an intermediary. The physical connection is ...
14
votes
3answers
1k views

WordStar's “column mode”

I've read that WordStar had a "column mode" which could be useful for making it act as a programmer's editor. But I've not found a clear description (or screenshots) of exactly what this mode was and ...
71
votes
12answers
16k 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 ...
5
votes
1answer
384 views

How old is Perl's “Plain Old Documentation” (POD) format and why was it called “old” initially?

I recently wondered how the "old" came into the "Plain Old Documentation" of Perl's documentation format "POD". Was it named like this from the beginning? If so, why was it considered old back then? ...
1
vote
1answer
205 views

What don't I understand about this LR35902 code?

The question you are now reading is about a comment on this question, about overflow bugs in some Pokemon game. A comment on that question says: It was Game Freak's first project. They just were ...

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