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5
votes
1answer
282 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 ...
6
votes
2answers
203 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 ...
4
votes
1answer
140 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 ...
55
votes
3answers
17k 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 ...
6
votes
2answers
630 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
189 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 ...
41
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
799 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 ...
10
votes
3answers
454 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
121 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 ...
12
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
920 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 ...
23
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
244 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
400 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 ...
9
votes
1answer
341 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 ...
16
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
239 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
144 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
93 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
314 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
318 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
235 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
133 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 ...
20
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 ...
8
votes
1answer
181 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
883 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 ...
5
votes
2answers
550 views

How can I ensure my computer design is not anachronistic?

I have a strange desire to make an imaginary competitor to the Atari 800 (6502 + different custom chips). As far as I can see people are mostly interested in making "my childhood computer, but with ...
4
votes
2answers
266 views

Commodore monitor to VGA or HDMI

I have this monitor, which I think is a Commodore 64 monitor. I would like to connect it to a pc. Anyone know how to convert VGA or HDMI to this connector format? I've tried searching, but so far I'...
19
votes
1answer
875 views

MOS 8502, just a 6510B?

I'm looking over what little I can find on the 8502, and from what I can see it appears to be a 2 MHz version of the 6510 with an extra I/O pin. Much ado about the speed, but the Atari's 6502B's were ...
12
votes
1answer
1k views

What manages Upper Memory Blocks (UMBs) in MS-DOS?

I had always assumed that EMM386.EXE was responsible for managing the Upper Memory Blocks - UMBs - the memory space between 640KiB and 1MiB in real mode x86. For example, on MS-DOS 6.22, help emm386....
0
votes
1answer
251 views

Which retro personal computers, if any, can use a modern day monitor? [closed]

I play around with emulators, and would love to go back to my roots, with physical ZX81, BBC Micro, Amiga, etc. Unfortunately, those all require a TV as output. I suppose that I could buy a cheap one ...
4
votes
1answer
236 views

Can the Nintendo 64 run code directly from ROM?

I've read that the usual way to execute code on the N64 is to use DMA to copy it from ROM into RAM, and then run from RAM. However, it seems that the contents of the ROM are directly visible to the ...
10
votes
3answers
2k views

Disable memory refresh on Z80

Is there a software method of disabling memory refresh on the Z80? Or would it be acceptable to create a hardware method of disabling the address bus during the refresh cycle? If I switch off the ...
3
votes
0answers
277 views

What is the cause of Trent's circuit board strategy? [closed]

For those of you who are unaware, professional speedrunner Trent Hall discovered a now banned strategy in Goldeneye 007. This strategy (called Trent's Circuit Board Strategy) consisted of plugging a ...
9
votes
1answer
2k views

Sources for some old BASIC games

Poking about in early issues of Dr Dobbs' Journal (the journal of the People's Computer Company, or PCC) I came across a listing for BASIC games available on tape. Many of these are widespread, but a ...
0
votes
2answers
111 views

ASCII ASA X3.4-1963 and Finite State Machines?

I'm reviewing the historical original ASCII standard. There are many control characters. Does anyone know the history of them and where finite state machines that made use of them may be documented? ...
7
votes
2answers
5k views

What was the point of the label on the bottom of the NES? [closed]

The original NES has a label printed onto it that the device would not "cause harmful interference". Why would they write that? Did people think the NES might be dangerous? Is this some kind of legal ...
2
votes
2answers
214 views

Is there such thing as para-emulation? [closed]

Is there such thing as a para-emulation? Like para-virtualization but for emulation? If so, where could I find a website that describes it?
16
votes
4answers
2k views

80286 real mode emulator for 8086

While trying to use a "modern" sound card (an Aztech Sound Galaxy Pro 16 II) in an XT compatible 8086 computer, I encountered the problem that the drivers and tools (like the mixer initialization tool ...
1
vote
1answer
222 views

Estimating contents of old printed circuit boards

I am sorry, if this is not a good place to ask, but is there any general rule of thumb about how much precious metals could you expect to get out from 197x(?) printed circuit boards, especially Soviet ...
3
votes
1answer
385 views

Why do parallel universes exist in Super Mario 64?

For those of you who are unfamiliar, Super Mario 64 is an extremely competitive speed game, and because glitches are allowed on most major leaderboards, many very talented glitch hunters have torn the ...
38
votes
1answer
3k views

Z80 CPU address lines not stable

I just got a Z84C0020PEC and wired it up to test it, using this circuit: Except that I've added LEDs to A0 through A9. It appears that A0 through A6 operate correctly, but A7 though A9 (I've not ...
6
votes
2answers
289 views

what is DMA and how does it work?

I've heard the term 'DMA' being used a lot in reference to older consoles. My very basic understanding is that it's a way for the console to access memory directly. But directly as apposed to what? ...
5
votes
3answers
383 views

How to use HGR2 (or HGR) on an Apple II

I am a big fan of the TV show lost, and I was trying to make the Dharma Initiative logo. But at certain point I couldn't add new lines of code and the final part of the logo was cut off. I tried to ...

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