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9
votes
3answers
413 views

Memory models for assembly libraries for Turbo C

Turbo C follows the Intel Memory Model where in Tiny, Small and Compact models calling a function is near but in Medium, Large and Huge models calling a function uses far calls. If I want to develop ...
3
votes
0answers
88 views

Monochrome CRT Repair - Horizontal offset

My CRT all of a sudden is shifted to the right. I cannot adjust it via the adjustment potentiometers, nothing changes when these are turned. If I increase the brightness, the whole screen turns green (...
19
votes
2answers
2k views

Exactly what color was the text on monochrome terminals with green-on-black and amber-on-black screens?

I am wondering what were the color shades and brightness of the text appearing on classic monochrome terminals? If I were to recreate the green-text-on-black-screen or amber-text-on-black-screen in ...
0
votes
0answers
140 views

What was stored in memory that was “unavailable to BASIC”?

On home / personal computers (such as before 1984), a machine might be described as having 24k RAM, but only 18k of that available to BASIC. If the machine had BASIC and the OS (or BIOS) stored in ROM,...
0
votes
1answer
98 views

ZX Spectrum: What is the “T” state value, with reference to sound?

I have that awesome book - Zx Spectrum ROM Disassembled (correct the title if I got it wrong), where the author wrote about the audio code in the ROM and referring to "T" state, "... T200... T5000, ...
8
votes
2answers
1k views

Did any 360-compatible machine implement registers in core?

In the early days of transistors, when they cost on the order of a dollar each, it was possible to implement CPU registers with magnetic cores (the technology used for main memory at the time) instead ...
2
votes
2answers
164 views

How did IBM's “Mag Card” drive and magnetic media work?

In the 1970's IBM popularized an early word processing solution using their popular Selectric typewriter line and something called "Mag Card". This video demonstrates the system in operation. The ...
23
votes
5answers
4k views

What type of interpreter were most 8-bit BASIC implementations?

I’m a big fan of early/mid 1980s personal computers like the Amstrad CPC, Commodore 64 and the Sinclair Spectrum. One thing these computers all had was a version of BASIC. Well known ones being MS-...
5
votes
1answer
477 views

How can I read a 5-1/4 drive on 1996-2007 equipment?

In my organization's archive I just found some 5-1/4" floppies, presumably IBM PC 320/360k. They contain information that we have on paper, but I'd really like to have on electronic media, not least ...
2
votes
1answer
105 views

What was the first company to sell an IBM compatible punchcard reader?

Punchcards were the primary way to get information into computers up through the sixties. The familiar eighty column format was designed by IBM, and was a factor in the later de facto standard eighty ...
2
votes
1answer
64 views

What are the differences between the various HxC Floppy Emulator hardware options when used with an Apple II?

I have an Apple IIc for which I would like an FDD emulator and I am considering buying an HxC Floppy Emulator to use with it. The Slim model does work with the Apple II, as demonstrated in this video. ...
31
votes
10answers
12k views

Were there ever 12-, 24-, 48-, etc bit processors?

After seeing this question, I was struck with an intense curiosity to know: Were there ever processors with word sizes that aren't powers of two, specifically after the 8-bit byte became the industry ...
3
votes
4answers
355 views

Were there any games/software that used a resolution or resolution-mode higher than what was advertised available on the machine?

Were there any games/software that used a resolution or resolution-mode higher than what was advertised available on the machine ? On home / personal computers between anytime - 1984 . Without ...
6
votes
2answers
1k views

What should be the waveform for ZX Spectrum tapes?

I am digitizing about 40 tapes with programs for the ZX Spectrum. I am somewhat puzzled by the waveform after digitization. The signal of most cassettes is meander-shaped. One of the cassettes can ...
-1
votes
3answers
260 views

Were there any games/software that used memory beyond what was advertised available to BASIC on the machine?

Were there any games/software that used memory beyond what was advertised as available to BASIC on the machine ? On home / personal computers any time before 1984 . Without needing to plug in any ...
21
votes
8answers
5k views

What other tricks were there to get more data onto floppy disks?

I remember using a utility back in MS Dos 3.3 days, called maxi-disk, that somehow magically managed to get 420K on a 360K 5 1/4" disks. I assume it managed it by destroying some redundancy like a ...
11
votes
1answer
447 views

What is the “Data Language” paper referenced in RFC 309?

RFC 309 is an announcement of the 1972 Data and File Transfer Workshop announcement. The suggested reading section has 12 entries, 11 of which are RFCs and the last of which is: 8. Data ...
5
votes
1answer
263 views

What is the C64 disk drive “Jiffy” protocol?

There seems to be something called the "Jiffy protocol" used for some fast load systems. I know of the JiffyDOS product, which seems to require replacing ROMs in both the C64 and the drive, but it ...
4
votes
2answers
165 views

Are there any open-source C64 DOS wedges and fast loaders?

The ever-so-popular EPYX Fast Load cartridge for the Commodore 64 included a DOS wedge (adding commands such as $ to list the files on a disk, /filename to load a file and @ to show the disk error ...
0
votes
0answers
82 views

What are the differences in system support between the various HxC Floppy Emulator hardware options? [closed]

There are several different hardware platforms for the HxC Floppy Emulator. The project itself (or its partners) offers hardware for sale and build instructions for "Rev C," "Rev F," "Slim" (all ~$70-$...
3
votes
1answer
125 views

Can't install El-Fish on MS-DOS 6.22

El-Fish is a fish tank "game", where you have virtual fish on your screen. The game has no goal, it's more like an interactive screen saver. I got my version from a number of different sources, one ...
51
votes
3answers
16k views

What is the “two-drive trick” that can read Amiga disks on a PC?

Standard belief is that the floppy disk controllers used on PCs are incapable of reading Amiga floppy disks, due to the PC disk controller expecting a very specific low-level format of disks, whilst ...
5
votes
2answers
602 views

Were any DOS games (or software) known to use VBE/AF?

Were there any MS-DOS games or graphics software that were known to take advantage of VESA BIOS Extensions/Accelerator Functions (VBE/AF)? some of the functions defined in the standard are ... Bit ...
7
votes
1answer
176 views

What is the exact bus protocol used by the C64/C128 REU?

The Commodore 64/128 RAM Expansion Units used a DMA controller to move data between the REU's RAM and system RAM (or I/O space). One would set the addreses, length and direction for the transfer (or ...
39
votes
2answers
8k views

Why were some early PC 3D cards unsuitable for 2D graphics?

Some of the early PC 3D graphics cards such as the 3dfx Voodoo Graphics cards had a passthrough port to enable them to switch to a secondary card to display 2D graphics. I am curious to know why these ...
17
votes
1answer
1k views

How does the C64 get an accurate TOD clock on 50 Hz power?

The C64 has two Time of Day (TOD) clocks, one in each of its 6526 CIA chips U1 and U2. These calculate time based on a 60 Hz or 50 Hz input to the TOD pin (pin 19); the clock input frequency assumed ...
11
votes
2answers
792 views

What are my modern options for loading programs and data files on the Apple IIc?

I've recently acquired an Apple IIc. The internal 5.25" drive does seem to make appropriate noises at boot, but I do not (at least not yet) have any floppy disks, with software or otherwise. It's an ...
7
votes
3answers
414 views

Why are NES cartridges grey while Famicom are rather colourful?

I've parsed a lot of websites and can't find answer anywhere. But still wonder to know why famicom cartridges are so colorful and different, but American and European cartridges grey only?
3
votes
2answers
115 views

Archimedes emulator “archie” PCFS file metadata format?

Archie, an older Archimedes emulator for DOS had a feature called "PCFS" that allowed Archimedes files to be stored on the filesystem of the machine running the emulator. The files themselves were ...
11
votes
3answers
1k views

Getting data from Seagate ST-238R drive

Hello: I have an old Seagate ST-238R drive. I'm the original owner and it stopped working in the early-90s when I foolishly deleted system files to make room for a football game. (I was 12 at the time)...
8
votes
3answers
892 views

How to implement bus sharing / DMA on a 6502 system

Was it possible for NMOS based 6502 system operate in the following fashion: while 6502 is not touching the bus one custom chip sets up memory read op, then two chips read the data off the bus at the ...
21
votes
1answer
2k views

What is a dropfile?

After reading Charles Duffy's comment on Was there a clearly identifiable "first computer" to use or demonstrate the use of virtual memory?: I had a computer science professor around 1999 ...
6
votes
2answers
241 views

Why isn't the 'restrict' keyword useful in SDCC when compiling for Z80 target? [closed]

Context SDCC claims to support C11. I use it to write games on Z80 target (for fun and experience). C11 defines restrict C11 specifies the restrict keyword on pointers, which can improve generated ...
12
votes
2answers
312 views

What is the Circuit for a 16K or 32K MSX computer cartridge?

This question is about the old MSX-1 computers. I have a game I wrote, as a ROM file, and I now want to play it on a real MSX computer by putting the game into cartridge form. The game has been ...
24
votes
4answers
5k views

Was there a clearly identifiable “first computer” to use or demonstrate the use of virtual memory?

The NPR.org news article and podcast How The World Has Changed! Science During The 40 Years Of 'Morning Edition' includes the photo below with the caption Before the introduction of the personal ...
8
votes
0answers
251 views

Why didn't Wozniak's interrupts work on the Apple I monitor program?

In his autobiography, Steve Wozniak recounts[1] his difficulty getting interrupts working on the 6502 microprocessor: The next step was to debug the 256-byte monitor program on the PROMs. I spent ...
15
votes
1answer
1k views

How does single-stepping on the 8086 interact with internal and external interrupts?

The 1979 version of the 8086 family user's manual is available at different places in the internet, see 1,2,3. It seems there is no newer version available. This manual documents the single-stepping ...
14
votes
1answer
223 views

What differentiated the Master System's Sega Card format from cartridges?

I know that the Sega Master system had two primary game formats: cartridges just like the NES and other game consoles of the time and the "Sega Card" which was a 2mm thick plastic card with contact ...
7
votes
2answers
138 views

What are the most common Apple II disk image formats and what hardware disk drive emulators can use them?

Archive.org has plenty of Apple II disk images, such as this DOS 3.3 image which is a .dsk file. I also see .nib and .d13 files, e.g. in this ASIMOV LISP collection. There seem to be further formats ...
16
votes
2answers
2k views

How to decode an audio file which contains an MSX BASIC program? [closed]

I have an audio file in WAV format, which supposedly comes from a cassette sound file. Moreover, it contains a BASIC program, but I don't know how to decode it. I have tried to convert the wav file to ...
13
votes
1answer
1k views

What was the first operating system that supported preemptive multitasking?

What was the first operating system that supported preemptive multitasking? By preemptive multitasking I mean that user processes were able to run in a time-sliced manner without special programming, ...
4
votes
0answers
90 views

MICRO 800 assembler?

I'm reading (well, writing...) about the FLOW language and it mentions the "MICRO 800 assembler". This was in the early 1970s, and I can't imagine what this might be. The context suggests it was on ...
6
votes
2answers
298 views

Get exact position of raster beam on C64/C128

By reading register $D012/$D011 or when pausing the execution of an emulation in VICE starting the monitor and entering io d000, it is possible to get information about the current rasterline. For ...
7
votes
2answers
313 views

What's the best way to hook up an external power supply to the Apple IIc without a 7-pin female DIN plug?

As seems to be typical with Apple IIc purchases these days, mine came without the external power supply. I have ordered some 7-pin female DIN plugs and other adapters that will let me plug a modern ...
6
votes
1answer
231 views

Did the CPU test on the Apple //e Diagnostics utility do anything?

After reading about the Apple //e diagnostics card, I noticed on the screenshot below that it reports a CPU test and that the microprocessor is OK: So I'm curious did the PROCESSOR TEST actually do ...
0
votes
0answers
130 views

100-pin connector to FPGA/SOC, can I auto-detect if attached to NES, SNES, Genesis, N64, GB, GBA?

If I have a 100-pin connector that may be connected to any of several known devices (NES, SNES, Gameboy, and so forth), can the device somehow auto-detect which device it's connected to? For some of ...
19
votes
9answers
6k views

Why does the single dot entry exist in file systems?

There is plenty of literature about its meaning, the current directory, but I would like to ask about why such thing do exist in first instance. While CHDIR .. usefulness is obvious, i.e. go to the ...
3
votes
2answers
184 views

virtual addressing in device drivers

Sun's SBus is particular for having virtual addressing and address translation even for device drivers. Any other buss design which had this peculiarity ? Check out Ben Catanzaro's book The SPARC ...
7
votes
1answer
168 views

What's the difference between the DOS HIMEM.SYS and the Windows 3.x version?

An installation of DOS (e.g. MS-DOS 5.0) will typically include a statement in its CONFIG.SYS such as DEVICE=C:\DOS\HIMEM.SYS. When installing Windows 3.1, it's setup comments (REMs) that line out, ...
10
votes
1answer
747 views

Why is the 'echo' command called 'echo'?

This is an essentially trivial question, but anyway: several operating systems have a command to display a specified text string on the terminal, or standard out, or whatever (depends on system to ...

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