All Questions

1
vote
0answers
46 views

Why did SAM on the Apple II use its own DAC?

From the comments on this question, the SAM on the Apple II seemed to use some proprietary hardware to produce the waveform. (I am not counting the option to produce a horrendous 1-bit PWM using the ...
0
votes
1answer
138 views

VGA to CGA (RGBI) signal

Does anybody know how I can go from an analog RGB signal to a TTL RGBI signal? Is there a good circuit for this out there somewhere?
4
votes
2answers
85 views

Tools for creating disk images on Mac Plus

I got BMOW's floppy emulator and have been pulling a bunch of files from 30 year old floppies (which have a miraculously low rate of failure) onto my SD card. One of the things I wanted to copy was a ...
8
votes
2answers
1k views

What is the meaning of M in the Z80 statement ADD A,M

Recently I have been trying to compile CP/M 2.2 from source. When I try to assemble, everything works except for the instructions ADD A,M and SBC A,M, which the assembler returns a syntax error. I ...
9
votes
1answer
313 views

Why was BASIC on the Commodore 64 one byte shy of 38KiB?

When you power up a Commodore 64 you are greeted with a friendly message telling the user it has 38911 BASIC bytes free. 38,911 is one byte shy of a 38 KiB (1,024 * 38 = 38,912). What was the reason ...
12
votes
2answers
748 views

Cassette tape storage formats

I just came across this excellent article on cassette tape storage formats. One thing confuses me though... in the "all digital" examples, like Figure 1C, what exactly ends up on the tape? That is, ...
4
votes
2answers
131 views

Can you replace an Apple IIgs battery with regular AA alkalines?

I have a IIgs that I clipped the battery out of a few years back. I'm thinking I want to replace a battery in there, but before I spend money on a product like this one, I'm trying to figure out if I ...
9
votes
4answers
264 views

For fast scrolling DOS games, when was Mode13h preferred over Mode X?

Back in the DOS days of gaming (more specifically, 80286 - 80486 era), developers typically needed to choose between using the chunky and easier Mode 13h or the more complex "Mode X" that provided ...
14
votes
3answers
395 views

Is there a line printer sound simulator?

To improve "authenticity" of a mainframe simulator and for an additional nostalgic effect, I'd like to add sounds of a line printer to it. They should be similar enough to the original sounds for ...
21
votes
3answers
4k views

Why does an instruction include the address of the next instruction on the IBM 650?

The IBM 650 seems to be a load-store machine. One advantage of a load-store machine is that the instruction can be shorter because there's less pressure to pack more information into it. But the IBM ...
12
votes
2answers
423 views

Why did Windows pick 260 characters as the maximum path length?

I just got burned by the 260 character path limitation in Windows. Why did Microsoft decided to limit paths to 3 characters for drive + 256 characters + 1 character for the terminator? Mac OS of the ...
6
votes
1answer
257 views

Multiple mass storage controllers on Amiga 500 or 2000

I'm in the process of restocking a lost collection of retro machines, including a couple of A500s, a 500+ and 2 A2000s (rev 4.1 and 6) in various states of disrepair. For one of the 2000s I would ...
1
vote
0answers
14 views

What is this NOR feedback loop in the AGC Cross Point Generator II? [migrated]

This feedback loop looks similar to a LFSR, however there are no registers present. It looks to be some kind of oscillator. There seem to be three inputs to this component, IXP10 (pin 111), STBE (pin ...
4
votes
2answers
222 views

Patent barriers to IBM mainframe compatibility?

'Blue Magic: The People, Power and Politics Behind the IBM Personal Computer' is an excellent book, but it makes one claim I cannot quite make sense of. Page 13 of the hardback edition says: "Lowe ...
4
votes
1answer
232 views

What happened to EYRX?

In 2001, Eyring Corporation released a 32-bit reconfigurable RTOS called EYRX. I remember downloading the documentation and programmer guide from their Web site. Strangely, no traces of that OS can be ...
6
votes
2answers
408 views

Why was the Hobbit withdrawn from the UK market?

The Hobbit is a Soviet computer which was built to be compatible with the ZX Spectrum, but with some extensions. For example it has more memory and can run CP/M. The Hobbit had favourable reviews in ...
5
votes
2answers
267 views

What were the main uses of the large CRT and light pen on early PDP computers?

My first earliest experiences with "large" computers were an HP-2100 and a sigma-7, using a teletype and punch cards/line printer respectively. I've stumbled upon an old image of a PDP-6 and PDP-6 ...
24
votes
7answers
6k views

What was the first mainstream advanced debugger?

What was the first mainstream development toolchain that provided advanced debugging facilities? By "mainstream" I mean something that was available on home computers, not mainframes or super-...
3
votes
1answer
141 views

How is the 320x200x16 graphics mode mapped in the IBM PCjr?

I've read that the PCjr supports a 320x200 pixel mode with 16 colors. But what I can't seem to find is how much memory that takes, how it's organized (chars?) or where it's located in memory. I'm ...
0
votes
1answer
147 views

Does the TurboGrafX16 store switches and/or flags in RAM?

Based the the specs I found for the TG16, it has 8 KB of RAM. I also found notes in the documentation of many opcodes that there is data stored in several "flags and switches" are these stored in RAM ...
3
votes
3answers
377 views

Pirated spreadsheet software introducing intentional errors?

Was there ever a case of a spreadsheet application introducing intentional floating-point errors when it detected that it had been pirated? Particularly errors that were small enough to go unnoticed ...
1
vote
1answer
273 views

Minimal DOS long filename driver

Am trying to run Latex + Emacs under DOS 5.0, and would currently seem to need long filenames. I have tried the DOSLFN driver but it prevents Emacs from running. I have 4 MB RAM in total. Is there ...
3
votes
1answer
160 views

Which pre-IEEE computers had a single precision FPU and implemented double precision floats in software?

Before the formats of floating point numbers have been standardized in IEEE 754 in 1985, different vendors had used many different floating point formats, some of them listed on the Data Format and ...
2
votes
2answers
244 views

How significant/pioneering was the TV Typewriter?

How significant and pioneering was the TV Typewriter, in light of things like calculators with CRT's from 1964 and various other things? I recently read that the TV Typewriter established the standard ...
2
votes
7answers
386 views

Name for rotary dial controllers?

Many years ago I was watching the news when I saw someone on a Sun workstation controlling the display using an external input device consisting of a series of rotary dials. Turning them rotated and ...
20
votes
4answers
4k views

Unlicensed home computer ports of arcade games

During the 1980s, it was quite common to see unofficial ports of popular arcade games released on home computer systems. For instance, Acornsoft (the software division of Acorn Computers) released ...
8
votes
5answers
586 views

What was the most popular CP/M terminal type?

I'm porting CP/M to a new/old machine (the Amstrad NC200 laptop). Running programs on it is no problem, but running interesting programs (i.e. WordStar, Turbo Pascal and Ladder) involves implementing ...
4
votes
1answer
164 views

Searching for Swedish Mac game from the early 1990's where you try to sneak out of the house

I was given a funny, obscure game for Mac sometime in the 1994 to 1996 timeframe. Unfortunately I have no idea what the game was called, but I'd like to track it down. The game, which was in color, ...
13
votes
2answers
1k views

Did the transmeta processor architecture work by binary translation?

Transmeta Corporation produced the Transmeta Crusoe Processor architecture. (Transmeta was also famous for having Linus Torvalds work there at the time.) We can see from the wikipedia article that ...
6
votes
3answers
476 views

Copying tapes “back in the day”

Back when I had a ZX Spectrum 48K, I had a friend that had a 128K and we would swap games for the weekend from time to time. We did try and make duplicates of the tapes (yes, I know, but we were ten ...
7
votes
2answers
2k views

Can anyone help me identify this computer?

In my loft there is a computer with no branding that needs a new CMOS battery, and one that has the branding 'Tri Data' which I can't find anywhere on the internet. It just shows a white screen as ...
3
votes
1answer
132 views

Ways To Test iMac G3 Before Buying

I am going to buy an old iMac G3 Over the next couple of days/weeks, and I want to make sure that I am buying a system with no problems. I usually ask for the serial number and good pictures before ...
1
vote
0answers
85 views

Symbian emulator to run Ngage games

I don't really know if this is the correct place to ask this, if not let me know where I should. I would like to know if it would be possible to run Ngage games on an existing Symbian emulator. There ...
9
votes
1answer
215 views

What exactly did Sony contribute to the original Apple PowerBook?

The first Apple PowerBook laptops were delivered in 3 versions in 1991: PowerBook 100, 140, and 170. These initial PowerBooks were overall a tremendous commercial success for Apple, and are regarded ...
57
votes
8answers
18k views

How was copying prevented when the first CD-ROM games were introduced?

Several ways exist to protect against the copying of games but, when CD-ROM games were first introduced, were there any measures taken by video game developers to prevent the copying of games?
5
votes
2answers
313 views

Why are the internals of NES Gamepaks so small compared to the case?

As you probably know, in the technology world, smaller is generally considered to be better. Companies compete to make the most portable phone, or the smallest laptop, but apparently Nintendo didn't ...
7
votes
3answers
721 views

what OS runs Zip drives? [duplicate]

I came across my old Zip drive and some Zip disks. I am curious what is on the disks, but my Windows system won't run them. Back in the day I thought that these would be the ultimate in archive ...
3
votes
1answer
101 views

In IBM SCRIPT/VS, what does DSM stand for in macros DSMFIG, DSMLIST

In (S)GML ancestor's IBM SCRIPT/VS, what does DSM stand for in macros DSMFIG, DSMLIST... ?
8
votes
4answers
2k views

Purpose of two disk drives on the Osborne 1

I recently discovered the Osborne 1 computer, and I noticed it had two floppy disc drives. What was the purpose of including two drives?
5
votes
1answer
132 views

Cross-Compatibility of UCSD p-Machine Versions?

I currently have Apple Pascal (and Fortran, and PILOT) running on an Apple IIgs emulator on Windows. As near as I can tell, it's UCSD p-System II.something. I also have a DOS-hosted UCSD p-System, IV....
4
votes
4answers
423 views

What is the basic logic behind the setting or ordering of keys in a keyboard?

I am a computer science student. I mostly work with computers and I am really wondering about the layout of keys in a keyboard. It is comfortable and easy. My question is this: what is the basic ...
2
votes
1answer
202 views

Why did Nintendo commission Sony to create a disk reader if the Famicom already had one?

The way I understand it, Nintendo's engineers couldn't figure out how to design a disk system for the SNES, so they commissioned Sony to do it for them. Why would Nintendo do this if they already had ...
3
votes
0answers
180 views

Can you tell me more about this robot?

A robot I can't find information on. I noticed an article and or advertisement in 1985, in the main city-wide newspaper ('mercury') in the city where this robot-factory was located. (I don't have ...
4
votes
2answers
407 views

What's with the empty space on this die?

Here is the Valvo 2650. (Also known by other names, in the UK as Signetics 2650). What struck me about this image is the amount of empty space! If you look at a modern-day chip, say a Skylake or ...
15
votes
2answers
2k views

What is the danger involved in trying to write already closed file with Commodore 1541 disk drive?

The Commodore 1541 disk drive and other IEC devices are self-contained computers. The operating system runs on the drive itself. This setup significantly improves the flexibility. As a side effect, if ...
14
votes
1answer
801 views

How does Apple ][gs hardware dithering work?

I haven't been able to find an easily comprehensible description of the super hi-res, dithered 16-color, 640x200 mode of the Apple ][gs. I can tell from the references I did locate, this is a ...
4
votes
1answer
235 views

Apollo Guidance Computer and heat dissipation

The Apollo Guidance Computer, was built on RTL which apparently can let off a lot of heat, and deployed in environments where we cannot rely on convection to pull the heat away (not only in low ...
4
votes
2answers
311 views

Floating Point on Konrad Zuse's computers

From what I understand, with floating point arithmetic, shifting values up and down is important, since a floating point value essentially is an equation like 2e×m. This supposition may be supported ...
5
votes
1answer
278 views

What was the first interactive OS to run each command in a new process?

I was prompted to ask this by another recent question about early Unix process structure. The more-or-less contemporaneous systems I'm aware of (built 1960s to 1970s) mostly gave you a software ...
37
votes
3answers
4k views

How did Apple ][ basic programs protect against listing?

I seem to recall from my high-school days that certain Apple ][ programs protected themselves from being listed and therefore modified. If you tried to do it, the machine would simply reboot. How ...

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