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8
votes
1answer
219 views

6502 False Reads and Apple II I/O

The 6502 series of CPUs has an interesting quirk: indexed loads and stores may perform a "false read", reading from the target address or a different address on a previous page. There are situations, ...
11
votes
8answers
5k views

Why were optical drives not used as secondary storage instead of magnetic drives?

What prevented optical drives from being used as the dominant secondary storage like the magnetic disk drives, in PCs? Was it entirely technical limitation or other issues like late development and ...
3
votes
1answer
169 views

Commodore 64 board dimensions

What are the dimensions of the C64 motherboard? I am specifically asking this because I am considering using a 64C case (these still seem to be in production) for an 8-bit homebrew machine. I wonder ...
16
votes
2answers
2k views

What are these weird long ISA slots on this 386 board? (not VLB)

In this image, you can see, from the right, a 16-bit ISA slot (occupied by a controller card), an 8-bit ISA slot, four more 16-bit ISA slots, and two of these strange slots that look like a 16-bit ISA ...
0
votes
1answer
397 views

What's the name of this CRT monitor?

What's the name of this output retro gaming monitor device? The following is a still from the Netflix production of 'Bandersnatch', a 2018 interactive movie, set in Britain, mostly in the year 1984. ...
14
votes
1answer
227 views

Is the “IBM standard character set manual” around?

From Wikipedia's code page article: Originally, the code page numbers referred to the page numbers in the IBM standard character set manual Is any version of this publication available? I'd be ...
39
votes
4answers
3k views

What was the design rationale behind multi-port and multiple connections (and back-connections) designs of the early protocols like NFS or FTP?

Originally, the FTP protocol connected back from the server to a client to actually transfer files through that new connections. 14 years later after the introduction of the FTP, the 'passive mode' ...
0
votes
1answer
93 views

How exactly does Leningrad contend the memory?

From what I understand of this answer, the Leningrad delays the Z80 during the M1 cycle so that the video generation circuitry can do its thing. I can see how M1 is "latched" (don't know if that's ...
12
votes
1answer
558 views

Odd tokenizing in Integer BASIC

While researching the underpinnings of Integer BASIC (IB), I came across an oddity I'm hoping someone can explain. Unlike MS-derived systems, IB converted numeric constants to their 16-bit ...
1
vote
1answer
133 views

How does the Spectrum +3 know how many files are in the disk's directory?

The Spectrum+3 uses a version of the Amstrad and CP/M disk layout. The Speccy version has a directory at the start of the disk after any reserved tracks and it can hold up to 64 files. Each ...
39
votes
1answer
7k views

What warning was given on attempting to post to USENET, circa 1990?

I recall a confirmation/warning message that read something like "this will post to thousands of sites... are you sure?" What was a typical such message in the days of pay-per-minute dialup access?
1
vote
0answers
145 views

Thinking through the design of a TTL video card: what memory chips and how to manage memory? [closed]

Inspired by Ben Eater's "Let's build a video card" aka "World's worst video card" two part projects on YouTube, I was inspired to consider designing a display adapter for my passive backplane TTL mini-...
27
votes
2answers
9k views

What is this programming language having PROC, DCL, LABEL keywords?

A 1980 paper called "Register Allocation via Coloring" contains something that looks like source code: P: PROC(MODE); DCL MODE BIT(1), (A1,A2,A3,A4,A5,A6,A7,A8,A9,A10, B1,B2,B3,...
10
votes
1answer
293 views

How did ZX81 assembly debuggers implement breakpoints?

What techniques were used for implementing breakpoints on the ZX81? Traditionally for the 8086 int 3h is used, for the 8080 on CP/M with DDT RST 7 as single byte replacements, 6502 has the BRK ...
1
vote
1answer
297 views

Were all NES games 16 kibibytes or less?

While searching on the Internet and Quora, I found disassemblers for Pac-Man, Galaxian, and Super Mario Bros. The thing that puzzled me, was while Super Mario Bros was arguably quite a complex game ...
3
votes
1answer
321 views

Is there any virtual hard disk driver over serial port?

NOTE: I'm not looking for a way to transfer files from Linux to DOS over Serial cable Is there any MS-DOS driver to enable a new hard-disk drive (let's say D:), using a disk image on another ...
2
votes
1answer
189 views

Who built the first electric/electronic adder?

The first electricity-based adder presumably used relays. (The electromechanical relay was invented for the electrochemical telegraph for repeaters in 1831 by Joseph Henry (1797-1878). I can't figure ...
9
votes
7answers
1k views

What are principles of vector CRT display? Simplest way to drive CRTs?

I am into playing with TTL to build 1970s style minicomputers. Aside from talking to them via some serial (or parallel) I/O port to a terminal, I am wondering about display output. This here is about ...
5
votes
2answers
459 views

What effect does exiting a FOR/NEXT loop early have on the TRS-80 Color Computer?

I have a subroutine with a for/next loop in Extended Color BASIC on the TRS-80 Color Computer that I would like, sometimes, to return early from. That is, to return from the subroutine from within the ...
3
votes
1answer
136 views

How to connect a Dragon32 to a HD TV?

The Welsh computer has a coax output and a resolution of 256x192, can I expect this to display at all on my Philips 50" 4K TV using the same input?
6
votes
1answer
326 views

What role does the 4-bit shift register play in the Leningrad video generation?

The Leningrad contains a shift register1, which I believe is loaded with data from the bitmap. This part loads 8 bits in parallel, and shifts each bit out in turn on the rising edge of a clock signal. ...
3
votes
2answers
241 views

How do I install Windows 9x on an older machine from a flash drive (or any other unconventional device)

Windows 9x is no longer common, and isn't commonly supported. While there exist many solutions to burning ISO to USB or other storage device, most fail at some point, with commonly useless if any ...
17
votes
3answers
3k views

Was there any automated unit testing prior to 1972?

Prior to 1972, was there any automated unit-testing? Did any assemblers include a testing a framework? I can find some academic journals on this topic from the late 70s -- most of which I don't have ...
0
votes
0answers
87 views

Siemens PG675 monitor problem

I have been working on an old Siemens PG675 and suddenly the monitor began to show a a distorted image (it shows this 1 when the should shows this 2). I could make a test of the screen, and it shows ...
-1
votes
3answers
209 views

What exactly has the windows OS relationship been towards MS server offerings?

This question is related to this one. I always was understanding that windows the OS was a companion app of sort in regards to the server offerings and that, yes you could use it for home use, but it'...
31
votes
7answers
10k views

How exactly did Windows become the OS of the home PC?

As far as I understand it, the whole personal computing revolution that Microsoft Windows did was not entirely by its own design. Is it true that the Windows OS at its core was originally designed to ...
2
votes
1answer
210 views

What is the first documented instance of video game console “Frying” and was this ever done with computers? [closed]

An early example of this can be seen on the Atari VCS (2600) console. With the "Space Invaders" game, one could hold down reset when powering on the machine and get a two shot mode. As word of that ...
11
votes
1answer
508 views

What additional hardware was required for BASIC on an Altair 8800?

I remember being aware of the Altair 8800 when it made it's mark, but only vaguely. Lately I found myself wondering what hardware was required for the Altair to get BASIC up and running. According ...
22
votes
10answers
5k views

Why did the original design of COM on Windows rely on the registry?

In the early 1990s Microsoft introduced COM (Component Object Model) which was widely used in various programming environments including Visual Basic 5 & 6. Also known as ActiveX (or at least if ...
8
votes
1answer
454 views

Was there ever a functional EGA emulator for the Hercules graphics card?

I used to use a CGA emulator (don't remember which one it was), that could show some gfx even in EGA/VGA-only games (when I selected EGA mode). I remember my frustration seeing some garbled graphics ...
9
votes
1answer
361 views

Why do PC DOS kernel files have the COM extension, even though they are not executable as COM files?

The PC DOS kernel is stored in files named IBMBIO.COM and IBMDOS.COM. Although they have the COM extension like executable files, neither of these files could actually be run from the command line, ...
4
votes
0answers
121 views

Where to find ancient wavy cursor program 'cyclops'?

In the period of about 1987-1988 I downloaded a small compiled program from a BBS in the 512 area. I don't know anything about the author but the file was named 'cyclops.' I can't be sure if it had a ....
0
votes
1answer
130 views

What did “double track” meaning in relation to floppy disks?

I mostly used 3½″ floppies back in the day but I also used 5¼″ floppies to some extent on Apple II's and TRS-80's. I was never exposed to 3″ floppy disks as used mainly on Amstrad microcomputers and ...
23
votes
7answers
4k views

Was it possible programmatically to manipulate the volume as well as the pitch on computers with no sound chip?

On early versions of many 8-bit computers like the Apple II, Spectrum, and even the IBM PC, there was no sound hardware other than the simple "beeper". Programmers made sound by hitting a hardware ...
0
votes
2answers
129 views

Can I use a 2.88MB ed floppy disk (3.5in) in a drive that uses the standard 1.44 HD DS disk?

I am using a Windows XP with an old accounting app, that will only back up to a 3.5 in floppy disk. But the backup requires a second disk to complete the job -- a pain. Would a ed 2.88 mb floppy (if ...
2
votes
1answer
154 views

How does the “backwards bump method” of SMB work?

In Super Mario Bros, the screen automatically starts scrolling once you are past X position 112. However, a strategy employed by many speedrunners of the game during level 4-2 is the "backwards bump ...
8
votes
1answer
347 views

How much time and how many people were required to develop Delphi version 1?

I would guess the compiler was primarily a modification of Borland's Turbo Pascal, while the Integrated Development Environment and Visual Component Library required a lot more development from ...
1
vote
0answers
41 views

Transfer a TeleDisk image of a 5.25 disk to a 3.5 disk

I am trying to power on an old Siemens PG675. It need a 5.25 disk but unfortunately it is missing. I found a TeleDisk image (.TD0) of this disk, and I would like to transfer it to a 3.5 floppy disk (I ...
-2
votes
2answers
187 views

Why did computers settle for instructions with multiple machine cycles instead of investing into larger ring counters? [closed]

On the 8080 and 8085 microprocessors, a LDA instruction took 13 timing(or T) states to execute. This could be solved by using a ring counter that could generate said 13 T states,as well as having ...
2
votes
2answers
292 views

How do microprocessors multiply without a “Multiply” instruction? [duplicate]

I was reading about the SAP computers(as I do), and examined the SAP-2 chapter of Paul Malvino's Digital Computer Electronics, hoping to learn about how a microprocessor without a multiply instruction ...
14
votes
6answers
5k views

How is it possible that they used to type “Mb” when they meant “MB” in printed computer magazines in the 1990s?

I've read some English and Swedish computer magazines from the 1990s, even late 1990s, and they frequently (maybe even consistently) use "Mb" to mean "Megabyte", even though "Mb" at least now means "...
7
votes
1answer
141 views

Did the Samsung SPC-650 have any hardware or firmware differences to the genuine Sinclair Spectrum+?

There was a clone of the Sinclair Spectrum+ in South Korea called the Samsung SPC-650 that looks identical to original British version with just an extra model number/logo. It even retains the ...
0
votes
0answers
81 views

Portable 386 that only ever beeps continuously; no video

I've acquired a late-80s portable 386 with builtin LCD in unknown working state. It only ever beeps continuously on boot, with no picture on either the built-in LCD or an external VGA-connected ...
3
votes
1answer
44 views

Is there a Spectrum +3 ROM disassembly available with the addresses of the instructions included?

In my experiments with Spectrum disk formats I've found myself looking into the ROM code a few times. Several Spectrum emulators have built-in debuggers that let me dissassemble and step through the ...
3
votes
1answer
164 views

How to emulate Pocket PC (PPC) 2003?

The OS is at least 17-18 years ago. Yet there is a lot of scattered information and dead ends, and no clarity on how to emulate Pocket PC 2003, the early precedent to Windows Mobile. How to emulate ...
4
votes
5answers
2k views

How does the shift key in a keyboard work?

The "shift" key on a keyboard is different from other keys as it can edit the outputs of the other keys on the keyboard. But how does it do it? I have one hypothesis on how the shift key does what it ...
3
votes
2answers
156 views

Why did the Apple Disk II version 3.3 change the boot protocol?

From what I understand, early versions of the Disk Controller II required that there never be two or more consecutive bit times without a phase transition (which would read as "0") but an upgrade to ...
0
votes
1answer
62 views

keyboard not operating electronica-bk-0100-01

I own a Electronica-bk-0100-01. I have only got around to connecting it up. Before that I opened up the system, checked for bad tracks, obvious issue etc. I also checked the end to end of the ...
0
votes
2answers
113 views

How do I know where the file directory is stored on a Spectrum +3 disk layout?

I'm trying to parse Spectrum +3 disk images. I only ever had a tape-based Speccy back in the day. The +3 had a built-in floppy drive but was late to the party and not that successful. It had the same ...
4
votes
4answers
928 views

How does the Spectrum +3 know whether a disk is bootable or not?

I've been looking through documentation on The Sinclair/Amstrad Spectrum +3 which was the only Spectrum that came with a built-in floppy disk drive. The disk format was based on The Amstrad CPC and ...

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