All Questions

3
votes
2answers
167 views

Is it possible to get a pdp7 [closed]

Is it possible to get an original DEC pdp-7, if so how much would it be? I've looked around the internet, but I'm not finding anything.
3
votes
2answers
286 views

EGA style 16 color dithering

I am trying to write a program in C# that will re-create the type of dithering used in many of the old sierra and Lucas arts games. I have looked up many different dithering algorithms and none seem ...
8
votes
1answer
823 views

Did CP/M provide compatibility for screen-based programs?

I refer here to 'screen-based programs' that are not actually graphical, but take full advantage of the screen as a two-dimensional array of 80x25 characters, as opposed to typical 'command-line ...
2
votes
1answer
197 views

What was the purpose of GROM (vs ROM) in the TI-99/4a?

The TI-99/4a had a cartridge slot on the front of the computer which accepted "solid state cartridges" (as TI called them). These cartridges would typically contain ROM (Read Only Memory) like many ...
8
votes
1answer
329 views

How can floating point addition be so slow on a BESM-6?

In the BESM-6 technical manuals — for example, in the ALU description, page 4 — there is a table specifying min/max/average instruction latencies in clock cycles (the last 3 columns; the ...
3
votes
2answers
279 views

When were sprites first displayed in the border area?

I assume one of the first undocumented effects on the VIC-II was the ability to display sprites in the (upper and lower) border area. I wonder how and when this was first discovered and used? Was it ...
12
votes
1answer
333 views

Why does AT&T syntax use * and $?

In a comment to an answer about AT&T assembly syntax, another-dave asked the following: DEC used #foo for an immediate operand in -11 assemblers; the Unix guys apparently preferred $foo, which ...
41
votes
13answers
15k views

How was it back then in 1984, when the Apple II had color, and the new Macintosh didn't?

I imagine it being a huge downgrade for some, not to have color on the Macintosh. Macintosh games were black and white in the beginning, while Apple II had color. I'm especially interested in ...
2
votes
2answers
280 views

USB ports for a 486 laptop (pccard 16bits)

I have an old laptop 486 with PhoenixBIOS which supports PC card 16bits( PCMCIA II/III). I am thinking about the possibility of adding a pccard 16bits with USB ports, mainly to read usbsticks or ...
5
votes
3answers
144 views

Opening or converting GFA Basic files to something readable?

There is a bunch of GFA BASIC for Amiga files (the source code for Blender's ancestor, Traces, downloadable here: http://zgodzinski.com/blender-prehistory/) that I would like to peek at. Despite my ...
10
votes
2answers
288 views

How to use the “darker” CGA palette using x86 Assembly?

For those of you retro developers out there, I am having a hard time figuring out how exactly to select the "darker" color palette in 320x200 CGA mode. Here's what I have so far: setup_cga_graphics: ...
17
votes
2answers
2k views

Why did the original Apple //e have two sets of inverse video characters?

According to Apple II Technical notes Mouse #6, updated January 1989, In unenhanced Apple IIe computers, the alternate character set contained two sets of inverse uppercase characters. In the ...
4
votes
2answers
241 views

Why does the Commodore 64 leave these pointers in Zeropage?

I'm trying to decide on what I can get rid of from the zero page, so that I can keep my own data there. Looking at this page, documenting what each of the zeropage locations do, I'm trying to figure ...
4
votes
3answers
524 views

Were some Atari 2600 games written in C?

I thought all Atari 2600 games had been programmed in 6502/6507 assembly language (plus whatever activated the Stella sound system), but at a party recently, a friend indicated that some 2600 ...
3
votes
1answer
261 views

Did any Apple II games use a “timing resistor”?

A science-lab program for the Apple II (I forget the name) had a board that plugged into the joystick port and included a "timing resistor". While I don't know what the program actually did with the ...
26
votes
6answers
4k views

Are there vintage or historical bitmapped fonts available for non-commercial use?

I'm looking for a source for one or a few 1-bit black-or-white bitmapped fonts used in the past, available in a set of sizes. Current incarnations might be available for large LED displays, but those ...
10
votes
4answers
998 views

Did any machines alternate between two video memory banks?

If a home computer or console has two banks of memory, A and B, then the following design is possible: The video chip only connects to bank A. The CPU connects to both. During active scan line, CPU ...
2
votes
1answer
244 views

Why does the SNES have a separate memory bank for sound?

According to https://snescentral.com/article.php?id=0088 the SNES has the following memory banks: Work RAM for CPU - 128 Kilobytes (CPU temp. storage) Video RAM for PPU - 64 Kilobytes (temp. storage ...
3
votes
1answer
165 views

What was the first publication documenting AT&T syntax assembly language?

What was the first publication to document what is (now) known as AT&T syntax assembly language?
2
votes
1answer
256 views

When were other inexpensive computers able to recreate “The Amiga Juggler”? [closed]

The Amiga Juggler was the 2nd very popular demo to appear for the Amiga Computer early in its lifespan. The demo was created by Eric Graham (who went on to develop Sculpt3D) using raytracing to both ...
1
vote
3answers
207 views

Connecting multiple computers through dialup

I have several IBM ThinkPads with an RJ-11 port that can be used for dialup internet connections. Currently I have one ThinkPad connected to a dialup modem, that connects to the internet through a ...
16
votes
2answers
2k views

When TCP was first invented, was the initial sequence number required to be random?

In current time, when a TCP connection is initiated, the initial sequence number is required to be random. But I am wondering, when TCP was first invented, was the initial sequence number required to ...
37
votes
1answer
5k views

How did Super Mario Bros. 3 create this tunnel vision effect?

In a certain section of World 8's map, the screen is black except for a small circle surrounding Mario (as seen below during this speedrun). After doing a little research, I discovered that the game'...
3
votes
1answer
87 views

Exidy Sorcerer: how can I load a program from cassette whilst within CP/M?

I have a file transfer program (sterm) that I want to load from audio cassette, but I need to load it into CP/M. Is this possible? Any suggestions how to do it? When CP/M is running either I don't ...
11
votes
3answers
502 views

Why have “room of dead” in Ultima VII?

http://wiki.ultimacodex.com/wiki/Quirks_of_the_Ultima_VII_Engine vaguely talks about this room being "necessary" to place seemingly "dead" NPCs and it was result of some challenge that programmers had ...
8
votes
1answer
317 views

How did Parallel ATA/IDE Independent Device Timing work electrically?

Back in the days of Parallel ATA (a.k.a. IDE) it was possible to connect two drives with a single cable. The ATA standard defines a number of modes with different speeds which the drives and the ...
1
vote
0answers
111 views

Old grid-based puzzle game with snakes that wake up when on the same row/column as you

I'm trying to find an old game: Played on an old computer, not sure which kind. (early/late 1990s?) Graphics were grid-based and "8-bit-seeming". Locations included - I think - plains and caves. ...
1
vote
0answers
85 views

Old C128 - normal to straight away pull 2 amps? [closed]

I'm trying to get an old C128 working again. Lacking a C128 power supply, I've attached a C64's power supply's 9VAC and am supplying 5VDC from a bench power supply (with a 2A limit at the moment). ...
2
votes
0answers
87 views

Which Nobel prize winners names besides Townes were used as code names for Fujitsu computers?

Fujitsu named its late 80s/90s personal computer FM Towns after physics Nobel prize winner Charles Townes. According to the sources (1, 2) I could find, using Nobel prize winners as code names was ...
3
votes
1answer
163 views

Operating systems (on support or recent) to install on a i486 processor computer [duplicate]

What operating systems would you recommend for this type of hardware? Though I keep the question text generic because answers can work for many others, but my specific case is a Laptop Siemens ...
23
votes
2answers
2k views

How many OS/2 viruses were there?

When I was in college, I remember IBM representatives trying to sell OS/2 Warp to students and teachers by saying that there were no (known) viruses for OS/2. (Of course, that didn't stop the makers ...
5
votes
2answers
265 views

Commodore 64 with red and white RCA cable

After discovering my old Commodore 64 in the garage, I wanted to test if it still works. The power light comes on but the video connection to a modern TV is obviously an issue, as mentioned here. Well ...
3
votes
1answer
351 views

Why did the Atari's have such clear displays?

Anyone that's seen an Atari 400/800 next to a VIC-20 or C64 will know what I'm talking about - the Atari display was much, much sharper. It had a similar advantage over the Apple II, and I seem to ...
5
votes
5answers
537 views

What systems had the lowest resolution ever that still allowed games to be made?

Just for fun, I wrote my own Chip8 interpreter/emulator and it works. The point is that it works in the terminal, meaning that a pixel is rendered using curses and a # character. For the Chip8 that'...
11
votes
2answers
2k views

Why does the Galaksija use SRAM instead of DRAM?

From what I understand, SRAM is more expensive than DRAM, but takes less support circuitry. That doesn't matter though, since the Z80 includes everything needed to refresh and support DRAM, doesn't it....
8
votes
1answer
231 views

What's the purpose of HOLD command in 6502 stack pointer

In the Block Diagram the Stack Pointer Register (S) has a HOLD command in addition to the LOAD and BUS ENABLE commands. The HOLD command is linked to the S/S output of the Random Control Logic. What ...
4
votes
2answers
215 views

Can a Harlequin ZX Spectrum clone be modifed to run CP/M?

The ZX Spectrum (and therefore the Harlequin) has its ROM from $0000 to $3FFF, while RAM further up to $5AFF is used for the screen (see Memory-Map). As CP/M expects RAM from $0000 upwards the two are ...
2
votes
1answer
216 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
174 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
118 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 ...
12
votes
2answers
561 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
817 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
164 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 ...
10
votes
4answers
392 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
462 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 ...
22
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 ...
13
votes
2answers
507 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
281 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 ...
4
votes
2answers
266 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 ...

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