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2 votes
0 answers
28 views

Identify MS-DOS 2D space adventure game c. 1992

Please can you help me identify a game I bought and played on my first PC around 1992? It was a 2D, top down game with a small spaceship that you controlled and remained centre-screen. It was a story-...
  • 379
2 votes
0 answers
38 views

Anyone up for decompiling some 8080 code for Kaleidoscope?

I came across a series of blog posts about Kaleidoscope, a demo program for the Cromemco Dazzler graphics card. The series implements an emulator for the system so that it could run this code again, ...
-2 votes
0 answers
52 views

Looking for a way to remove letters from a string in AppleSoft BASIC [closed]

I am working on a word processor and I need a way to remove letters. Here is my current code: 5 LET L$ = "" 10 HOME 20 GET A$ 30 L$ = L$ + A$ 40 PRINT L$ + "|" 50 GOTO 10 I will ...
3 votes
0 answers
88 views

Was the Zilog Z8070 ever mass produced?

I only recently came across a mention of the Z8070 FPU for the Z8000 family. According to some benches, it was very fast given its HMOS implementation and clock. Of the very little information I can ...
11 votes
5 answers
2k views

Do/did mechanical hard drives constantly spin the discs? [closed]

I have to admit that I didn't ever really think about how a hard drive worked until recently. I only had a vague understanding that there was (at least) one hard disc and some kind of "needle&...
  • 111
0 votes
0 answers
136 views

Looking for empty POKE addresses for AppleSoft BASIC

I am looking for empty POKE addresses for AppleSoft BASIC. My program needs to use a POKE to store strings, so I am wondering if it is possible to store strings using a POKE command. If it is not ...
11 votes
3 answers
2k views

Why doesn't the NMOS 6502 have the illegal instruction, STA immediate?

The 6502's instructions have the form aaa-bbb-cc, where cc picks an instruction group. Group 01 is the most regular and easy to understand. In this group, aaa picks an instruction from the list 000 ...
  • 35.2k
33 votes
2 answers
4k views

What are the three or four holes on the back of a 3.5inch floppy disk indicating and used for?

Why do 3.5 inch floppy disks have sometimes three and others four holes on the backside? What's the difference, what do this holes indicate and what are these used for?
  • 1,653
0 votes
0 answers
62 views

System 7.5 install fails (mac IIsi)

I have been restoring a rather iconic (and temperamental!) Mac IIsi. I have trouble installing System 7.5 on an IBM drive with Apple firmware that OS 7.0 installed just fine on. I am puzzled by the ...
  • 233
3 votes
1 answer
330 views

Is there a routine like FETCH, STASH and SWAP for transfering data between memory bank 0 and 1 on the C128?

The BASIC 7.0 of the C128 provides commands for copying a block of bytes between an REU (RAM expansion unit) and memory in Bank 0 or 1. For those who do not own an REU, is there a function for copying ...
  • 4,267
1 vote
1 answer
309 views

Why does Windows 95 not install so well from a Windows XP boot floppy? [closed]

EDIT: And this is why you shouldn't rely purely on memory for these sort of things. After some fiddling with my XP and Win95 disks, I remembered that the problems I was having were more likely related ...
3 votes
0 answers
130 views

Did any Dreamcast VMUs/memory cards have more than 200 blocks?

Dreamcast VMUs can store 128k in 200 "blocks". Third party memory cards increased the storage by having multiple virtual cards, each with 200 blocks. With some hacking it is possible to free ...
  • 14.2k
1 vote
0 answers
151 views

Real applications for the "weird" functions of the 74181 ALU? [duplicate]

Out of the popular but closed question 74'181 ALU why would anyone (have) use(d) these wild functions? I break off another part. We know why those many logic function exist. I am not listing them ...
1 vote
1 answer
139 views

74'181 missing zero flag but strange -1 (or all 1) flag, only makes sense in active-low mode?

Out of the popular but closed question 74'181 ALU why would anyone (have) use(d) these wild functions? I break out one aspect, that of a missing zero flag output. If I wanted to build a CPU with ...
3 votes
1 answer
94 views

74181 in odd carry logic in active high mode

Out of the popular but closed question 74'181 ALU why would anyone (have) use(d) these wild functions? I break out one part. I don't get the carry logic. Normally your addition works by giving A + ...
5 votes
0 answers
142 views

How many CP/M-86 copies were sold?

Approximately how many CP/M-86 copies or licenses did Digital Research sell across the product life of the operating system? Are there any data or estimates? I know the success of MS-DOS didn't leave ...
13 votes
3 answers
2k views

At what point did computing go from mainly performance- and functionality-oriented to security-oriented? Why? [closed]

I realize this question may have a different answer for each field of computing (enterprise vs. business vs. personal vs. field equipment), but there should still be an objective point in time where ...
9 votes
2 answers
665 views

74'181 ALU why would anyone (have) use(d) these wild functions? [closed]

Got myself a bunch of 74LS181, because they were cheap and they have been used in the VAX 11/780. And now I made myself a little tester breadboard where I am trying to figure this out in practice. My ...
3 votes
1 answer
195 views

Interpreting TRS-80 model 1/2 tape cassette audio

I got interested in writing my own code to parse tape cassette formats for a few platforms. I did OK with both Spectrum and Apple 2 tapes based on info I could find online. Speccy and Apple 2 seem to ...
  • 5,033
29 votes
3 answers
3k views

What exactly did the "UNFORMAT" MS-DOS command do?

I found only this: The UNFORMAT command is used to undo the effects of formatting a disk. The command is available in MS-DOS versions 5 and later. Source: https://en.wikipedia.org/wiki/...
  • 291
2 votes
2 answers
162 views

How do I save data from a program with CC65 [closed]

I wanted to have a calculator program be able to save a set of answers on a floppy disk or tape but I have no idea what I should do. I am aware that the "cbm.h" library can be used to load ...
0 votes
0 answers
111 views

Laser FD-100 5.25 drive isn’t working?

I recently inherited an apple IIc plus computer and it came with a 5.25 Laser Fd-100 drive. I noticed it wasn’t working so i opened it up and noticed the laser reader wasn’t moving across the tracks. ...
  • 1
5 votes
1 answer
124 views

How to avoid error when a macro package is included multiple times in ca65 assembler

Using the .MACPACK directive, predefined macro packages can be included in the assembler source code with .macpack name. For example .macpack generic defines macros like add, or sub (see https://cc65....
  • 4,267
9 votes
1 answer
263 views

When was let introduced to Lisp?

Similar to When was DEFUN added to Lisp? when was let introduced? It seems like a fundamental feature but unless I missed something even maclisp didn't contain it.
  • 511
17 votes
2 answers
4k views

What is this diskette drive?

I am preparing a BBC Model B micro computer for sale which has been in storage and needs cleaning. There is a 3½" diskette drive with it, which was unfortunately stored with the slot uppermost ...
1 vote
0 answers
120 views

How can software including drivers be moved from one windows (2000) installation to another?

I have a Windows 2000 system which no longer boots. We've narrowed it down to disk corruption of some Windows components, and a clean install of Windows should fix that. But there's some specialist ...
  • 351
4 votes
2 answers
181 views

Drive icons for LaCie Tsunami

I am restoring a LaCie Tsunami 240 external disk for the Macintosh. I found a replacement Quantum LPS240 and the hardware side is well on its way. This drive displayed a custom icon in System 7 (a ...
  • 233
3 votes
0 answers
113 views

Can MAME save to cassette tape formats other than WAV? [closed]

MAME seems to be extremely unintuitive to use and extremely poorly documented. But it supports a ton of machines, some of which I haven't found other emulators for, so I've been persevering with it ...
  • 5,033
1 vote
2 answers
99 views

Dump Mask ROM on MAB8421

I am trying to find a way to dump the rom contents of several MAB8421 microcontrollers. I know that on many 8048 MCUs, you can use the external access pin to dump the rom, but the 8421 doesn't have ...
8 votes
2 answers
2k views

Which order does the 6502 read its vectors in?

I'm looking at gianlucag/mos6502 and Mike Chambers' fake6502. They have observable differences in the way that they read the reset vector. Rubbermallet reads the $fffc first, and then $fffd. I'm ...
  • 35.2k
17 votes
1 answer
2k views

Why would installing a 486DX2 make the system freeze for minutes on boot?

In the mid-1990s, a friend of mine had one of those Compaq Presario desktop PCs that had an integrated CRT SVGA display built in the same cabinet as the CPU, in a similar fashion as the early iMacs. ...
  • 349
7 votes
2 answers
1k views

Can you load machine code programs for cassette tape on a TRS-80 model 1 level 1?

I'm trying out TRS-80 model I/III emulators. I know there was Level 1 and Level 2. I think this refers both to the ROM and the BASIC on the model I. Level 2 ROMs were a common upgrade to the model I ...
  • 5,033
9 votes
1 answer
555 views

x86 PC/Dallas Semiconductors RTC style general purpose NVRAM usage

The RTCs of x86 PCs commonly include some amount of general purpose NVRAM, e.g. the DS12885 has 144 bytes general purpose (GP) NVRAM. The ACPI Specification specifies some RTC also with GP NVRAM, ...
6 votes
2 answers
392 views

BASIC : POKE and PEEK prohibited on the same line?

Having been raised on an 8-bit Commodore, I was never afraid of PEEKs and POKEs. I remember trying to accomplish something on a computer, in BASIC, using PEEKs and POKEs, and discovering that this ...
  • 1,208
3 votes
1 answer
174 views

How to change graphics modes from BASIC on a Timex/Sinclair 2068?

I've got the Timex/Sinclair 2068 emulation working under MAME and wanted to play with its extra graphics modes the original version of the Sinclair ZX Spectrum didn't have. But despite an hour of ...
  • 5,033
15 votes
4 answers
1k views

Video playback software/formats for a 386?

Wanting to have my 386DX @ 20MHz play a video (any video), just as a demo. I'd prefer it to be watchable (eg 10fps and not a tiny 10x10 pixel) as opposed to a slideshow. What player software could I ...
  • 275
21 votes
2 answers
1k views

How did LaFarr Stuart's "Forth without an input buffer" work?

In Thinking Forth (also here), Leo Brodie writes: LaFarr Stuart...didn't like the input buffer, so he implemented Forth without it, and discovered that he didn't really need an input buffer. How is ...
  • 22.2k
29 votes
5 answers
4k views

What made some 8-bit BASIC interpreters especially slow?

Most 8-bit systems had a BASIC interpreter that ran at a rate roughly commensurate with the CPU type, speed, memory bandwidth and interrupt status. Some systems, however, had interpreters that ran at ...
  • 17.6k
22 votes
4 answers
3k views

Was it possible to cause persistent changes to a mid-1980s IBM-PC using POKE in GWBASIC?

TL;DR: Using the DEF SEG and POKE commands in GWBASIC, was there any way to make changes to an IBM-PC compatible computer that would (a) persist even after a reboot and (b) cause an increase in crash ...
  • 926
8 votes
3 answers
410 views

Why does CP1252 have these unused codepoints?

The CP-1252 (sometimes called Windows-1252 or many more stupid names) encoding has five unused codepoints, 81h, 8Dh, 8Fh, 90h, 9Dh. The placement of these is not immediately obvious to me. Are they ...
  • 35.2k
2 votes
2 answers
202 views

Is the volume wheel value wrong on the GBA schematics?

This GBA schematics says the GBA volume wheel (VR2 at the center bottom) is 30k ohms. Another schematics can be found here and it also says 30k. However when you do a ebay.com search for GBA ...
  • 383
6 votes
1 answer
774 views

Can I use a volume wheel with different specs for the GBA?

I bought a replacement volume wheel for the GBA. There are no other potentiometers available for the GBA. The original one has 30 kΩ as shown on the schematics. The one I bought has 10 kΩ and can be ...
  • 383
14 votes
3 answers
1k views

How can one do bitwise Boolean operations in later versions of Applesoft BASICs?

According to this answer, Apple changed the AND, OR, NOT operators in later versions of BASIC to perform Boolean instead of bitwise logic, so for example (1 AND 2) = 1. Which raises the question, how ...
  • 381
0 votes
2 answers
248 views

How did Atari RF output work?

I know that RF stands for radio frequency but what chip in the Atari handles the video output and does anybody know if something similar would work on a modern tv?
9 votes
0 answers
270 views

What's so different about Super Mario Brothers World T-1 that it doesn't look like level data at all?

Youtube video here: https://youtu.be/E6qRbk5Cscw?t=1127 Most of the glitched worlds are clearly ROM fragments of world data being loaded, most of them out-of-alignment and being rather messed-up. This ...
  • 953
11 votes
2 answers
2k views

How does MS-DOS 6 cache the DIR results?

I was wondering how the MS-DOS 6 DIR command works. I noticed that the floppy drive directory is cached so that the drive isn't read again when you run DIR a second time. In thinking there may be a ...
  • 2,853
5 votes
1 answer
1k views

How does the GameBoy Colors' display work in color?

I know the GameBoy originally worked in a 2bpp display functionality, with 4 shades of grey, but how does the GameBoy Color tiles work with colors? No website seems to have a obvious and ...
7 votes
1 answer
259 views

Software that emulated VGA high res mode on an EGA board

I have this very faint recollection from my late elementary school days back in the end of 1980s of a very specific piece of MS-DOS software that claimed to do what was an incredible thing to an ...
  • 349
8 votes
1 answer
397 views

BASIC Output to RS-232 with Tandy Model 100

I want to use a program like this on a Tandy Model 100: 10 REM COM Port SetUp 9600 8N1??? 20 PRINT "TRS-80 Model-100 is sending this out!" 30 GOTO 20 I need to know what line(s) to replace ...
  • 141
9 votes
1 answer
315 views

What were the typical game development toolchains for the pre-i386 IBM PC era

On i386 and beyond (assuming MS-DOS as the target OS and IBM PC as the target platform), my impression is game developers most typically used Watcom C / DJGPP plus one of the DOS extenders (DOS4GW, ...
  • 1,834

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