All Questions

6
votes
1answer
171 views

What's the difference between Kansas City tape standard and CUTS?

A number of a different computer systems use a tape encoding based on either the Kansas City or CUTS standards. There's a very brief overview on Wikipedia, but it's not clear what the difference ...
8
votes
1answer
1k views

Which operating systems for 80286 computers allowed a process to use more than 128k data?

Out of all the operating systems for the 80286 processor I found, only two make use of the protected mode's ability to load more than one segment for text and one for data. These are MS-DOS (through ...
2
votes
1answer
213 views

Which CPUs had instructions leaving data registers in an unspecified state?

When an ALU performs a floating point division operation using the non-restoring or the SRT algorithm, it maintains the current value of the "remainder" (in quotes, because it is not a true non-...
5
votes
0answers
154 views

Possible cause for C128 A/V output containing faintly coloured columns and failing shortly after?

I recently acquired a Commodore 128. It worked fine for about an hour, in both C64 and C128 mode, at the exception of some coloured bars, before displaying garbage and not booting anymore into any ...
4
votes
2answers
444 views

Why does R.O.B. wear “glasses”?

So recently, I've been playing Gyromite (which sucks), with R.O.B. (which also sucks), and I noticed that he comes with sunglasses that he doesn't actually need to work properly. This was the case ...
14
votes
1answer
2k views

How do accelerators and CPU cards work on the Apple II?

An Amiga 1200 exposes the entire CPU bus on the expansion port, so that an accelerator only needs to assert BR which causes the onboard CPU to stop all computation and electrically disconnect from the ...
5
votes
0answers
196 views

How many Amiga 3000's were produced?

While revisiting this question: Seeking details relating to Amiga 3000 serial numbers I began to wonder how many actual Amiga 3000's were produced by Commodore. I suspect (like most production ...
1
vote
1answer
132 views

Support for 5.25-inch floppy drives on IBM Thinkcentre 8187 KUR

I have an IBM ThinkCentre 8187KUR desktop system. It has a bay for 5.25-inch floppies but no support in the BIOS. My question is, can I put in a PCI card to support floppy drive access and run the 5....
2
votes
2answers
206 views

MS-DOS, save data from COM1: to file and display on console at the same time

I have a MS-DOS 3.22 laptop that will receive simple text data over serial COM1. I can make it save to file by doing TYPE COM1 >> data.log and I can make it show the data on the console with ...
3
votes
1answer
184 views

Windows 98 SE PC refusing to network using NIC/modems

The problem is basically as the title stated. I have a Compaq Presario PC from the late 90s running Windows 98 Second Edition. It was handed down so I'm not exactly sure what it went through in its ...
11
votes
1answer
191 views

Can I trigger the Amiga ROM debugger from the boot prompt?

Suppose I have an Amiga computer without any working boot disks. Is it possible to trigger the built-in ROM monitor (RomWack or SAD, see https://theamigamuseum.com/amiga-kickstart-workbench-os/guru-...
4
votes
3answers
249 views

How can I debug a Mac OS Classic application?

I have a Mac OS Classic application (a game) that I want to "debug". It has data files in a unique format than I am attempting to reverse-engineer. I've made some progress with a hex editor, but ...
2
votes
3answers
502 views

When did “Zen” in computer programming become a thing?

What the roots of the endless analogies to Eastern philosophy, 1990: Zen of Assembly Language: Volume I, Knowledge 1995: Zen and the Art of the Internet: A Beginner's Guide (Prentice Hall Series in ...
1
vote
2answers
274 views

Using C64 floating point kernal routines with 16 bit integer

How to use floating point kernal routines for 16 bit arithmetics such as: $1234*$ABCD or $1234/$ABCD ?
1
vote
1answer
94 views

EPROM software at conflicting addresses on Nascom computers

Nascom computers had a wide range of software distributed in EPROM; as the Z80 didn't really have very good support for relocatable code, however, this means that each program is required to be ...
16
votes
5answers
2k views

Was 1991's Hellcats the first instance of incremental screen updates?

In case you have never seen it, 1991's Hellcats was a seminal release on the Mac. It ran at full 8-bit color and could, on a newish machine, drive three 1024x768 screens at the same time. Nothing on ...
4
votes
1answer
427 views

Where can I find macrofun.hlp?

In the days before Visual Basic for Applications, the macro language for Microsoft Excel was called XLL. The syntax was similar to that of ordinary Excel formulas, except for two things: Macros were ...
11
votes
1answer
575 views

What undocumented 8085 instructions is Steven Morse referring to in “In The Beginning”?

In S. P. Morse's 1980 allegory, "In The Beginning", he writes And Intel said, "Let there be an 8085 with an oscillator on the same chip as the processor, and let an on-chip system controller ...
5
votes
1answer
167 views

Macintosh System 6 on Quadra?

System 6 is not officially supported on 68040 Macintoshes, but has anyone successfully run System 6 on an early Quadra, e.g. the Quadra 700?
5
votes
2answers
267 views

Do TG16 games and software suffer from lag frame similar to NES Super Mario Bros?

As a speedrunning fan, I've watched hours of Super Mario Bros speedruns, and have heard the term "lag frame". I don't think it's similar to typical computer lag, but instead an extremely technical ...
24
votes
6answers
8k views

How did the early Macintosh computers update the display?

This question is about the Macintosh 128k, but if you can give an answer which describes one of the other very similar machines, that's good too. The bitmap was 512 by 384 pixels. Assuming that one ...
9
votes
2answers
1k views

What's the relationship between the Nascom computers and the company Lucas Electrical?

Researching the Nascom 2 computer, I found these schematics for the system. Interestingly, after the schematics for the computer itself, there is an added schematic for a disk controller to use with ...
5
votes
1answer
271 views

How to install System 7.5.5 on a Macintosh SE/30 using floppies?

I have a Macintosh SE/30 with a formatted Disk. I'd like to install the latest System 7 on it that will run. According to Wikipedia that should be 7.5.5. According to several sources Apple has made it ...
7
votes
1answer
392 views

Colorful print ad in ca. 1990 magazine

I'm trying to find a software ad in a comic book style that I remember from one of my father's computer magazines in the early 1990s. I know this is a long shot, but somebody might recall it or even ...
7
votes
1answer
817 views

Why does this 6502 code push a function address onto the stack before calling?

I am learning how to program the Atari 800 by examining some tutorial code that came with the IDE/Assembler I am using. I am using the MADS assembler for this. putchar_ptr = $346 csrhinh = 752 ...
8
votes
5answers
1k views

PDP-11 stack may grow in either direction?

According to this answer, the stack grows downward. It's in §4.4 of the cited document: As another example, the DEC PDP11 range has a hardware stack which grows with decreasing store addresses....
8
votes
1answer
478 views

RAM for Socket 7 Motherboard - 64MB sticks appearing as 16MB

I hope this is the right place to ask this and that it is "retro" enough. I have a Socket 7 machine that I am working on. It's my 1st PC from childhood that I restored, and now I would like to ...
13
votes
2answers
3k views

Why was the 6809 so expensive?

The 6809 was released in 1978, but looking at the usual source for price quotes for old computer components, Byte magazine, I cannot find any quotes for 1979. December 1980 lists it at $38, compared ...
8
votes
2answers
757 views

How useful were the 6809/6309's indirect addressing modes?

Much like the VAX, the 6809 and 6309 have a preponderance of indirect addressing modes (in VAX parlance, "deferred"), though neither go so far as to include a VAX-like doubly-indirect mode. To what ...
14
votes
2answers
4k views

What does “jmp *” mean in 6502 assembly?

Right now I am learning 6502 assembly. Currently I am using the MADS assembler to program for the Atari 800. This program is just a small tutorial program that came with the assembler zip file I ...
11
votes
4answers
1k views

How to use USB flash drives with Windows 98 SE?

I have a Compaq desktop computer running Windows 98 SE. It's been handed down a few times, and I don't recollect it ever being online but it does have a version of Firefox from 2007 so I could be ...
2
votes
1answer
176 views

What is the format of a TurboGrafX instruction (modified 6502 instruction set)?

What is the general format of TurboGrafX processor instructions? For example, and this is made up: one word for opcode + two words for flags + one word for every parameter listed under that ...
3
votes
1answer
197 views

How big is one word in TG16 hardware?

My goal is to recreate the TurboGrafx at gate-level, however there isn't much documentation of the system, probably due to its relative obscurity. What I want to know is how long one word (processor ...
4
votes
1answer
167 views

Why did PAL Apple //e motherboards have the AUX slot inline with Slot 3 instead of near the power supply?

The Apple II architecture supported 7 memory-mapped expansion cards which could be optionally installed towards the rear of the motherboard in individual expansion card connectors. On the Apple //e, ...
1
vote
2answers
272 views

Resource for 6502 assembly directives?

I am currently learning about 6502 assembly. One of the documents I am learning about it from is a super mario bros. disassembly document. When I was reading the code I noticed part of the code had ...
7
votes
2answers
2k views

6502 CMP instruction doesn't compare as expected

I am trying to code in 6502 assembly and for some reason the CMP instruction doesn't work. For example: CLD LDY #$03 LDA #$00 LDX #$05 CMP Y BEQ Equal STX $0200 Equal: BRK ...
4
votes
2answers
187 views

Method for adding firmware to a Commodore 64 expansion card?

The C64 expansion port can and does support multiple IO devices without conflicts. There is 0.5 KiB that is decoded for $DE00-$DFFF, using /IO1 and /IO2 on the expansion port. As long as the devices ...
19
votes
2answers
3k views

How did the ZX80 store both a useful program and screen memory?

I have a vague recollection from my earliest days that the ZX80 only shipped with 1K of RAM. If this RAM was used to store both the program and the contents of the 32x24 screen, wouldn't that mean ...
11
votes
1answer
1k views

How did the RCA1802 'call' and 'return' instructions work?

The RCA 1802 processor was used in a number of systems such as the ELF and COMX-35, and also apparently in the US space program (with its hardened variant). From memory, it had a rather unusual set ...
7
votes
2answers
399 views

When did Intel undergo the SEX change?

I am reading the book "The 8086 / 8088 Primer Second Edition" by Stephen P Morse. In it on page 54, it says The 8086 provides instructions to facilitate the task of sign extension. These ...
1
vote
0answers
123 views

Are Unisys ClearPath Libra mainframes still in use in Australia?

By use, I mean are they still actively being developed for. I know this is the case in New Zealand and USA. In particular, is ALGOL code still being written on them?
1
vote
3answers
173 views

Was parsing or operating systems the first user of dollar sign as end of string/input?

According to the question Why did DOS use dollar-terminated strings? DOS uses dollar-terminated strings, inherited from CP/M which used them because DEC also used dollar as the string terminator. ...
14
votes
2answers
2k views

First language with C-like memory management

This is a nerd question but I can’t find anything in google. So, in which programming language did the classical memory management system first be implemented? I mean the division into value types (...
9
votes
2answers
858 views

What is an “unused” memory address?

Reading this page on Commodore 64 memory structure and usage I stumbled across a cell where the table claims that this memory is unused. What exactly does this entail? Does this mean that if you ...
31
votes
7answers
9k views

Last computer not to use octets / 8-bit bytes

I am old enough to remember computers that were not octet oriented. E.g. the first that I used was an ICL 4120. It had 24 bit words which were, when necessary, divided into four 6-bit characters. ...
13
votes
1answer
269 views

C-64 Exchange News Service

I am trying to recall the name of a peripheral I use to have for my C64 in the 1980s. I believe it was called Exchange or X-Change. You hooked it up to your cable TV service and it would decode a ...
10
votes
3answers
776 views

What is the instruction set of the Z4?

I am able to find a few instructions, such as: Fin (presumably "Fine", as in the end of a musical score, ends a program), Fin', (a conditional Fin), St (possibly "Start" -- the need for this is ...
5
votes
3answers
401 views

What to check before powering on TRS80 Model III in unknown condition [duplicate]

Having managed to source a TRS-80 Model III that I'm told hasn't been powered on for quite some time (and I suspect this is a massive understatement), I'm worried that the first thing that might ...
8
votes
2answers
539 views

Instruction set support for multiplication with a constant

Before integer multipliers in silicon, several cpus had some support for multiplication. For instance SPARCv7 has the MULScc multiply-step instruction (several other cpus also have this). As far as ...
1
vote
2answers
237 views

Acorn System 1 - is it a collectable? [closed]

I have one of these things gathering dust at home: Acorn System 1 I have the original manual (when I find it?) too. It did work, the last time I powered it up, 35 years ago. Should I throw it in ...

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