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11
votes
2answers
3k views

Are BIOS ROMs interchangeable among different vendor's PCs?

For PC/AT, 80386, and 80486 machines from the late-1980s through early 1990s (e.g. retro machines, not modern), can you expect to pull a BIOS ROM from one machine and have it work fine in a different ...
47
votes
2answers
8k views

What is the origin of this bizarre advert of people wearing swimsuits in a room with computer hardware?

This image of people wearing swimsuits in a room with computer hardware popped up on Twitter recently. Where was this advertisement published, and what computing product or service is it offering?
7
votes
5answers
1k views

Pulling my hair out over a 4-bit architecture, there ought to be some law here somewhere, is there? [closed]

I am trying to build the most simple CPU possible. And doing it on bread boards. There is a popular movement, one of the biggest protagonists of that being a certain Ben Eater, who is a good teacher, ...
8
votes
0answers
195 views

Behavior of lesser known illegal M6800 opcodes

The M6800 had a few illegal opcodes, including the (in)famous HCF (Halt and Catch Fire). The following illegal opcodes were revealed in BYTE Magazine, December 1977: $14: NBA $87: STAA immediate $C7: ...
7
votes
1answer
116 views

Understanding the DMK disk image file format used by TRS-80 emulators

DMK is a low-level disk image file format used by TRS-80 Model I & Model III, Tandy Color Computer, Dragon 32 & 64, and MSX emulators. It's capable of representing copy-protected disks and all ...
3
votes
0answers
28 views

On the TRS-80 models I and III when is the directory track number written in the third byte of sector zero, and when in the second byte?

Earlier I had found that many but not all TRS-80 Model I and Model III disks begin with the three bytes 00h FEh 11h. This is the beginning of the boot sector where the CPU interpets it as a NOP ...
3
votes
0answers
228 views

What is this 2000s-era Windows XP or earlier educational computer game? [closed]

So I asked this question a while back asking for help with identifying a retro computer game, and got the answer I was looking for. Thus, I've decided to ask for help identifying another retro game ...
8
votes
1answer
112 views

Is scratchpad register 15 directly addressable on the F3850 (except as QL)?

The Fairchild F8 CPU, the F3850, has 64 scratchpad registers. The first 12 of these are directly addressable by several instructions. For example, the opcodes $CX add the contents of scratchpad ...
11
votes
1answer
160 views

What are the added opcodes for MC6801/MC6803?

What new opcodes were added to Motorola MC6801/MC6803? Background for the question, and what I've figured out so far (correct me if I'm wrong): The Motorola MC6801 (and MC6803) had an "enhanced ...
51
votes
14answers
11k views

Did many programs really store years as two characters (Y2K bug)?

The claim that programs stored dates as two ASCII or similar characters because computers were limited in resources seems wrong to me because it takes more memory than one 8-bit integer would. Also in ...
4
votes
1answer
234 views

Back in the day, were games coded to run better with more (not faster) RAM? [closed]

Let's say the year is 1999 or something like that. I have a PC with 400 MHz, no graphics accelerator and 64 MB RAM, and try to run some Need for Speed game or something. I notice that it goes laggy. ...
7
votes
1answer
196 views

How to make bootable CD with multiple games for CDTV

How to make a disc with multiple titles on it, available to select from a menu? Did anyone have any luck creating a bootable CDTV disc using software mentioned on English Amiga Board and is is ...
3
votes
2answers
105 views

Which Commodore CDTV models came with keyboard with grey caps

I've noticed on the Big Book of Amiga Hardware site, that CDTV keyboard came in 2 versions, one with black caps, one with grey ones. Which one came first and with which model of CDTV?
22
votes
2answers
2k views

Which is the minimum set of interrupts/functions I should implement in a replacement BIOS for a home made IBM PC class computer?

I'm at the early stages of implementing a home-made IBM PC class computer (maybe AT class, I don't know yet). The CPU will be an actual 8088 chip, but everything else (except memory) will be ...
3
votes
2answers
146 views

Printing German umlauts with cc65

I want to print German texts with umlauts with a compiled C program on the C64. I'm aware that these characters are not in the charset and that I will have to change the character set. However, it ...
1
vote
1answer
154 views

Why didn't the Whirlwind I use a high persistence crt or something?

Why didn't the Whirlwind I use a high persistence crt or something ? On this video Whirlwind I at 1:48, you can see the text being diplayed, it is only very briefly visible, apparently they would take ...
2
votes
3answers
161 views

'What' used spare memory on the TMS9918?

'What' used spare memory on the TMS9918 Video Display Controller? By 'what', was it Something pre-installed on the computer like Bios or Basic or something, I assume the main cpu s themselves were ...
8
votes
4answers
429 views

Why did later CPUs use microcode instead of PLA's?

If you look at a die photo of a 6502, about forty percent of the chip is taken up by what's obviously microcode, both by its regular structure and by the obvious need for such from the instruction set,...
8
votes
5answers
2k views

Why did raster displays require semiconductor memory

This source states that introduction of raster graphics display began in mid-1970s only after affordable semiconductor memory had become available on the market. Would it be at all possible to make a ...
5
votes
2answers
192 views

Why does the Galaksija's latch include some kind of address remapping?

The Galaksija has a 6 bit latch used for various bits and bobs, notably the part of the scanline counter which contributes to character generation, but also, it has a bit for clamping A7 high, and ...
4
votes
1answer
226 views

Address of ISR for Interrupt INT 13H

The memory address in the Interrupt Vector Table of an 8086 associated with INT13H should be: 13H * 4H = 4CH But a book I was referring to says that: The physical address of the memory location ...
55
votes
19answers
16k views

Why were computer customers called “Users”?

The term User for computer hardware and software customers has been universal for as long as I can remember. It has always applied to both hardware and software customers - There were "Lotus Users" ...
2
votes
1answer
156 views

Are all Slot 1 motherboards compatible with Coppermine?

I want to put together a Pentium III tower using a beautiful Coppermine SL3XL CPU I found with a Slot 1 form factor. However, I noticed that many slot 1 motherboards do not officially support ...
16
votes
2answers
2k views

Is there a Commodore 64 emulator that can profile running code?

I am developing some software for the Commodore 64, and I am concerned about its runspeed. Is there an emulator that can report, after running my code, where exactly it spent most of its time? I'm ...
18
votes
1answer
2k views

Identifying late 1990s embedded 486 UNIX-like system

I'm trying to identify the operating system on a Thermo-CRS C500 robot arm controller. From the specifications I know it runs on a 100 MHz 486 processor, and has 4 MB RAM and 2MB of flash/NVRAM ...
4
votes
2answers
201 views

What is the purpose of ROM switcher mods in CDTV

I've seen a lot of information on CDTV ROM switchers, but it is still unclear to me what is the actual purpose of it. As I understand it allows some compatibility with A500 games, but this disables CD ...
4
votes
0answers
121 views

Are there any copies of ICL MS-DOS 4.1 available for emulation?

The first PC I ever owned was the ICL DRS PWS 300 as described in this press release. It was originally supplied with a copy of multitasking MS-DOS 4.1 (and Windows 1.0, which isn't mentioned in the ...
5
votes
1answer
104 views

How to get GOTEK to work with CDTV?

I'm trying to connect Gotek drive to my CDTV using external caddy (amitek). The drive has 3 digit LED display, after boot i can see F-F. When I insert Flash drive it detects images on it, I can ...
1
vote
0answers
218 views

Is the thirty something year old RJ45 jack as small as it will ever get? [closed]

Why are micro-ethernet adapters not a thing? A physical adapter that takes our thirty year old standard sized RJ45 jack on one side and and plugs into a TabletPC on the other. Every other form of ...
2
votes
3answers
194 views

Webservers: When did www.domain.net/dir/file.html first not point to $WWWROOT/dir/file.html but to something virtualized?

If I'm not mistaken, the first webserver simply served all files and directories in a certain local directory (WWWROOT) in the identical hierarchy at a certain domain. This is in line how e.g. an FTP ...
1
vote
1answer
127 views

What are the sizes of the hex nut drivers in the classic “nine piece” computer toolkit [closed]

Back in the 1990's many vendors sold those cheap nine piece kits that held, among other things, two Philips screwdrivers: #1 and #2, a couple of flat head screwdrivers, and a pair of hex nut drivers. ...
4
votes
2answers
289 views

Aside from legacy systems, are there any contemporary uses for magnetic core memory?

Core has some interesting properties (nonvolatility, high reliability, resilient to radiation) that might make it useful in some situations. I know early versions of the computers on the Space ...
7
votes
0answers
134 views

Need help checking an ADC0808 / ADC0809 chip in a arcade shooting game

Main Question: How can I check a ADC0808 chip to determine if it needs to be replaced or if my issue is something else? Any advice you can offer is SO appreciated! ADDITIONAL INFO When the arcade is ...
17
votes
4answers
3k views

How did dot matrix printers do Landscape?

In the 1980's, few people could afford laser printers and other page printers (e.g. inkjets) were not yet affordable. Most had inexpensive dot matrix printers with tractor feeds, such as my own Star ...
3
votes
1answer
175 views

What bug in first version of game Karateka for Apple 2e cause this game reset in Apple 2c?

If try start first version of game Karateka for Apple 2e in Apple 2c, Apple 2c will restart after computer read game from disk after few seconds. Later version of Karateka for Apple 2c work. What is ...
27
votes
3answers
4k views

Why did many 9-pin printers use only 8 pins for graphics?

In the answer to another question about printers, the following claim is made about 9-pin printers: The Epson MX-80, upon which many other printers were based, had nine round pins which were ...
1
vote
1answer
124 views

Opening a .zbd file

I have a .zbd file from my military service with sensitive information on it from 2004. I have downloaded the ZoomBrowser from Canon, it does not recognize it as a file. I downloaded the Zebedee ...
32
votes
4answers
5k views

Why was 'echo on' chosen as the default setting within batch scripts in MS-DOS?

In my experience, just about every single MS-DOS (and thus Windows cmd) batch file starts with the line @echo off, to silently switch off echoing of the commands in the batch file to the console. This ...
1
vote
1answer
202 views

Using Bresenham's circle algorithm (or another alternative algorithm) to draw an arc [closed]

I'm trying to create some graphics function for a ZX Spectrum (Z80) machine in assembler. I already have the basics except for the arc. I know that there must be some way to draw an arc using the ...
20
votes
3answers
3k views

Typical dpi of dot matrix printers available in the 1980s

I have several printouts from what is presumably a dot-matrix printer, dated 1987. When zoomed in on these, you see the usual stair-step patterns on diagonal lines. However, it's difficult to ...
5
votes
2answers
327 views

Why when outputting registers' value the result is a wrong fluctuating value in a Z80 CPU?

I got an EEPROM AT28C64 and loaded it with instructions with my handmade STM32 EEPROM programmer, the instructions are very simple: Load A register with decimal number 85 which is, in binary, ...
7
votes
1answer
289 views

IBM PC 5150 board layout

How did the parity check DRAM chips work? In particular, is there a reason for the gap in the motherboard (IBM calls this system board) between the parity check DRAM and the "normal" DRAM ...
3
votes
1answer
136 views

Loading a Tandy CoCo or a Dragon 32 machine code program from cassette with multiple “name blocks”

For the Dragon 32 and the TRS-80 Color Computer I've found two documents describing how loading from cassette tape works:Dragon 32 doc, CoCo doc. They both say that a standard program consists of a ...
12
votes
2answers
3k views

How did the /dev file system work in early Unix?

UNIX did not have support for virtual file systems (vnodes) until 1986. S.R. Kleiman, “Vnodes: An Architecture for Multiple File System Types in Sun UNIX,” Summer USENIX 1986 I remember this quite ...
8
votes
1answer
554 views

On the LR35902, what does the assembly 'LD (HL-),A' do?

I'm working on implementing the instructions of the z80 chip inside a gameboy for an emulator. I'm starting with the instructions in the boot rom that sets everything up. I've implemented the first 3 ...
1
vote
1answer
48 views

How to configure HDD controller for CF in CHIPS LeAPset 117 (R1.09) bios

I'd like to use Compact Flash with 2,5" IDE adapter in i386 laptop. The bios is CHIPS LeAPset 117 (R1.09) and it requires specific configuration for HDD in order to work. I have 4GB CF card, where I ...
4
votes
2answers
698 views

How does the RST operation of GameBoy (SHARP LR35902) work?

The GameBoy CPU Manual talks about restart operations on page 116. Each of these operations push the current address onto the stack, and then jumps to a specific address (0x00, 0x08, 0x10, etc, ...
5
votes
2answers
1k views

Is solder-on memory upgrade an option here and how to check it

I have this system with 2MB onboard RAM, but I noticed there are additional soldering pads to the right from memory chips (NEC 424400-80L, but there are also TOSHIBAs TC511664JL-10 on daughter board ...
26
votes
3answers
3k views

What were the HW specifications for the actual PC speakers, before they were replaced by buzzers?

Back in the early 2000s, I remember that, what were at the time older, PC cases had actual loudspeaker instead of the buzzer, which was popular as the PC speaker on the PC cases of the time period. ...
18
votes
3answers
3k views

Where to buy a 6502 chip

I want to purchase a 6502 40 pin CPU in order to verify if my 6502 is faulty, I've seen I can buy from Hong Kong but would prefer closer (to the UK), RS and CPC don’t seen to have any. Most answers ...

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