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4
votes
2answers
198 views

ZX Spectrum scroll waiting for user input problem

I'm trying to compile a C program with z88dk for the ZX Spectrum. Using printf(), when the text hits the bottom line of the screen on line 24 the program stops executing until a key is pressed on the ...
1
vote
5answers
839 views

How binaries are generated using Punched cards? [duplicate]

I thought that punched cards already represent the code in binary since a hole means 0 and rest positions mean 1 on a punched card. But then I read that you could use punched cards to present the ...
11
votes
0answers
442 views

Why did some MOS 6502 packages have holes in them?

Someone was recently selling an early MOS 6502 CPU on Ebay (date code 0277) in a ceramic package that had a couple of holes in it. You can see them clearly (under the tape, which presumably was not ...
8
votes
3answers
606 views

What are my options for fast bidirectional transfer between a C64 and a 1541?

Since asking a similar question, which is really exclusively about using KERNAL to transfer between disk drive and computer, comments, answers and others hint at the fact that using the KERNAL really ...
10
votes
1answer
1k views

How fast are transfers between the C64 and the 1541 floppy drive?

I am developing some software for the Commodore 64, and my intention is to use the 1541 as a coprocessor. I'll have the 1541 compute some data for me, and then retrieve this data over the serial line. ...
26
votes
4answers
8k views

Why are the homing bumps on D and K on Apple keyboards?

Some Apple keyboards, such as the Apple //e, some early Macintosh models, and the venerable Apple Extended Keyboard have the homing bumps on the D and K keys instead of the standard F and J keys that ...
14
votes
2answers
2k views

How was a line of Commodore 64 BASIC code stored in its memory?

I am reading up on old C64 stuff and I am using the Vice emulator to play with it. Currently I am studying about how the C64 stored BASIC programs in RAM. This is quite clear (it starts on address $...
4
votes
2answers
320 views

What was the timeline for monitors becoming immune to physical damage from invalid sync values?

When I first got into using Linux around the turn of the millennium, XFree86 was still in use, with the associated use of the xf86config command to manually set everything up, and the warning that ...
5
votes
1answer
695 views

Did this analogue computer from 1960 really have Internet?

If you zoom in this image, to the leftmost, white "cell" in the middle "row" of the machine, it says, in the bottom, "INT NET": https://upload.wikimedia.org/wikipedia/commons/c/c6/PACE-TR-...
5
votes
8answers
292 views

What 8-bit microcomputer systems multiplexed multiple physical ports on a single controller?

The NEC PC-8201 had three serial interface ports on the back, "RS-232," "SIO1" and "SIO2." These were all driven by a single IM6402 USART, switched between each physical port via bits 7 and 6 of IO ...
6
votes
2answers
1k views

Were internet costs ever billed per packet?

I'm currently studying the TCP layer, one of the main references is the 1981 Internet Engineering Task Force's RFC. One of the paper it cites is a paper published by the Internet Electric and ...
6
votes
1answer
205 views

How are Amiga Kickstart Relocation Files (.RTB) created?

Examples of Amiga Kickstart files (ROMs) can be 256k (1.2/1.3) or 512k (3.0/3.1) binary files, located at $FC0000-$1000000 or $F80000-$1000000 Several programs are able to "soft-kick" Amigas, i.e. ...
8
votes
4answers
343 views

Why do N64 cartridges use 2 different technologies for saving to the cart?

I've noticed that most N64 cartridges don't have batteries, but about 12 of them do. According to a google search, the cartridges without batteries use EEPROM and the cartridges with batteries use ...
22
votes
4answers
4k views

Why was NEC able to wrestle PC graphics standards away from IBM?

The dominant standards for PC graphics in the 1980s were the ones introduced by IBM. This included MDA and CGA with the original IBM PC, followed by EGA shortly after the PC/AT, and then VGA with the ...
7
votes
1answer
271 views

What is a “stunt box”?

According to the Free Dictionary, citing the McGraw-Hill Dictionary of Scientific & Technical Terms, a "stunt box" is "A device to control the nonprinting functions of a teletypewriter terminal." ...
4
votes
1answer
221 views

Is it possible to detect Horizontal Blanking (HBL) on an Apple II

Is there a way to detect HBL and or VBL on an Apple II, and if yes, how it's done?
3
votes
3answers
349 views

Understanding the meaning of the term “Modifying a software program” in a book

In his book The Silicon Jungle David Rothman mentions several times the term "modifying" or "customizing" a software program. e.g. Chapter 8: And then the consultant didn’t even supply instructions ...
5
votes
3answers
721 views

How does the Apple II read lines for video display from the text-mode frame buffer?

(This question applies also to the low-resolution graphics video buffer, since that uses the same frame buffer as text mode, just displaying it differently.) As described on page 1-12 et seq. of The ...
13
votes
1answer
447 views

Did Babbage's Analytical Engine lack indirect addressing?

As I understand it the analytical engine could only refer to memory by variable cards that had the explicit address printed on them, see https://www.fourmilab.ch/babbage/cards.html. For instance the ...
23
votes
4answers
5k views

What is DRAM refresh and why is the weird Apple II video memory layout affected by it?

I've roughly known the concept for years, but never really understood it. Back in the day, two types of RAM typically used in home computers: static and dynamic RAM. Static RAM (SRAM) was apparently ...
8
votes
3answers
405 views

Were any Apple 1s sold with non-ROR 6502s?

The first production runs of the MOS 6502, in mid-1975, had a bug in the ROR instruction that caused MOS to "remove" it from the instruction set by omitting it in the intial documentation. An updated ...
19
votes
1answer
2k views

When low-level formatting a floppy, how does one ensure any existing sector markers are overwritten?

If a formatted floppy diskette is reformatted with a low-level¹ format, how does the formatting routine make sure that any previous sector markers are fully overwritten? In particular, how does it ...
34
votes
2answers
7k views

Why didn't Apple sue Commodore over the Amiga's GUI?

Famously, in the late 1980's Apple sued Microsoft over the "look and feel" of Windows 2.x. The claim was that Windows breached Apple's copyright by being too similar to the Mac UI. Apple ultimately ...
8
votes
2answers
2k views

First x86 Software Development Manual

These manuals are now called “Intel® 64 and IA-32 Architectures Software Developer Manuals”, and the current version is 71. What was the original name of this manual and when was it released?
2
votes
1answer
259 views

Kermit pauses when switching between apps in windows 3.1

I wrote a batch file which sends some files over a serial port in Windows 3.1, using kermit.exe. The problem is: when the user switches between apps, the kermit batch will freeze till the next time ...
6
votes
2answers
376 views

What happened to the S1 operating system?

(Computerworld, Vol. 17, No. 41, 1983, p. 49) Additions: Robert Knight, formerly of Princeton's computer laboratories, is [...] the creator of S1, which he had running on an IBM Instruments ...
4
votes
1answer
97 views

Version list for TOPS-10?

So, does anybody have a list of TOPS-10 versions? I haven't been able to find any information aside from versions 7.03, and 7.04. are these lost to time? To clarify, I'm not asking for the software, ...
20
votes
3answers
2k views

How were the 70's and 80's coin-op programmed?

How were the 70's and 80's coin-op programmed? What tools did a programmer use? Nowadays a programmer can use a PC, an IDE to program, test, use breakpoint... but in the 80s? How could a programmer ...
25
votes
3answers
2k views

What do the '80/40' and 'keyboard' buttons on my Apple IIc do?

Above the keyboard of my Apple IIc there are two buttons that say "80/40" and "Keyboard". On my machine, they both kinda feel broken. When I press them, they recede into the case and remain there for ...
5
votes
1answer
273 views

What did the Datapoint 3300 character font look like?

We know from the Datapoint 3300 Maintenance manual the characters were formed on a 5x7 grid, and on page 2-55 we have an "A". But is it known what the rest of the characters looked like? According ...
6
votes
1answer
286 views

How did the 6809 achieve source-code compatibility with the 6800?

The 6809 has 59 instructions, as compared with 78 on the 6800. So far as I can see, the 6809 lacks instructions that the 6800 has, such as aba, eorb and the transfer instructions (tba, tap and the ...
0
votes
2answers
143 views

RTC 16bit I/O read/write

Why can't RTC (0x70, 0x71) read and write 16 bits? such as Mov ax, 0xa8f Out 0x70, ax But I found in a 286 BIOS that they did this: (BIOS ID string: S286-6181-101590-K0) 00005357 B87253 ...
6
votes
2answers
202 views

Why do PDP-10 skip instructions also load an AC?

A recent question on the PDP-10 "JUMP versus JUMPA" prompted this question. For reference, see this page of instructions. The SKIP instructions all skip based on the content of a specified memory ...
4
votes
1answer
173 views

Why did the CDC 6600 expand the word size to 60 bits?

According to http://www.quadibloc.com/comp/cp0201.htm The CDC 1604 used 48-bit floating point with 11 bits exponent and 36 bits mantissa. There was also a double precision format (which I believe was ...
12
votes
2answers
963 views

How is the Apple II text flash mode timed?

On the Apple II, there are three 40 column text modes: normal (white on black), inverse (black on white) and flash. A text screen can contain a mix of text in all three of these modes. Flash mode is ...
5
votes
2answers
226 views

What are typical causes of IC failure in early microcomputers?

When troubleshooting older electronics, the usual culprits tend to be connections and capacitors. The "solid state" components, if they have failed, usually in the role of victim e.g. bad voltage ...
10
votes
2answers
2k views

How did X talk to the video card before DRI/DRM?

The way I understand Linux history, in the early 2000s, Linux introduced the DRI/DRM mechanism and framebuffers, so userland can write to the graphics card directly. Before that, "console" linux was ...
33
votes
2answers
9k views

On what computer did “JUMP” mean “don't jump?”

This question triggered a brain cell. I remember a computer architecture, possibly one that was known for its beautifully symmetric instruction set, with an assortment of distinct mnemonics for ...
3
votes
1answer
172 views

Could the PDP-11 console be accessed “raw” by software?

My rough understanding of the lights-and-switches console that many PDP-11 models had is that they were not hardwired into the CPU itself or anything, but implemented as just another Unibus device. ...
3
votes
4answers
935 views

Why use an ADC or SBC with immediate zero on a 6502?

I'm perusing the Apple I version of BASIC, later known as Integer BASIC on the II. In several places I see... ADC #$00 or SBC #$00 Unless I'm mistaken, these mean add/subtract zero. What ...
1
vote
1answer
113 views

No syntax-error message from MSX BASIC `SCREEN` command

On bluemsx, for the machine just labelled MSX, adding a '.' full-stop after SCREEN 2 and typing various different types of rubbish does not generate a syntax error message . SCREEN 2.11111 Noticed ...
5
votes
1answer
332 views

How many hours of labor did it take to assemble a minicomputer?

A minicomputer like the PDP-8 contained several thousand discrete transistors and other components, all of which had to be soldered by hand, and that was among the simplest computers on the market; ...
53
votes
7answers
9k views

Why did the MS-DOS API choose software interrupts for its interface?

Access to the DOS API was done through the INT 21h x86 instruction. This was always counter-intuitive to me, coming from 8-bit systems that accessed system services by calling subroutines through a ...
4
votes
4answers
452 views

Z88DK ZX Spectrum “%f” printf not working

I'm attempting to compile a program in C for the ZX Spectrum using Z88DK. However, I'm facing an issue when trying to use printf to print out the value of a float. The code I'm trying to compile: #...
14
votes
2answers
1k views

DEC Alpha: why no 8/16-bit load/stores?

The first version of the DEC Alpha had no load/store instructions for 8 or 16-bit values; if you wanted to deal with data of such sizes, you had to do it by shifting and masking values in registers as ...
0
votes
2answers
154 views

How did the 6800's comparison operations work?

Does anyone have a quick primer to the way the 6800's compare-and-branch instructions worked internally? I'm referring to the instructions like BLS that compared a value in memory to the accumulator. ...
1
vote
2answers
187 views

How to get rid of keyboard latency in atari800 emulator?

I use the atari800 emulator v. 4.2.0 on windows 10 and linux in latest version. (https://atari800.github.io) I notice an annoying keyboard latency of up to 100-200ms (keypress-to-click and ...
-1
votes
4answers
406 views

Was it true that Microsoft actually created software for early Apple devices?

Is it really the case that there was a port of Microsoft Word and Excel that was one of the first really successful software to feature on a Apple device? Did Microsoft software actually have a ...
4
votes
4answers
361 views

What was the DEC Type 30 vector graphics display used for?

The DEC PDP-1 had, unusually for its time, a vector graphics display. According to https://en.wikipedia.org/wiki/History_of_Digital_Equipment_Corporation Most systems were purchased with two ...
49
votes
7answers
20k views

Why was the Kickstart 1.x “Insert floppy” graphic so bad?

Anyone who used an pre-Kickstart 2.0 Amiga will be very familiar with the "Insert Workbench floppy" image: I realise that this is subjective, but the image has always stuck me as ... well, a bit ugly....

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