All Questions

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 ...

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 ...

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 ...

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 ...

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 ...

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?

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. ...

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 (...

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 ...

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. ...

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 ...

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 ...

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 ...

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 ...

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 ...

I have a working C128 desktop that I'm using to troubleshoot a non-working C128D-CR. I suspected a problem with CIA 2 on the C128D, so I swapped its chip labelled "6526A" with a 1988 year stamp with ...

According to this answer to Why were early personal computer monitors not green? they had a severe disadvantage in that you had to choose between 'too dim' and 'rapid burn-in' whereas amber could ...

If I attach a 16 KIB EEPROM to a 6502 or similar, and put some kind of operating system on it, it will run fine, but won't have access to any other chips. So, when a Commodore VIC20 had 5k of ram and ...

I have asked several questions about IRIX compilers. I have gone from GCC to searching the web for Java Development Kit for IRIX (which I wasted 6 hours trying to find). Is there any website that has ...

I've got ImageDisk installed on my old 486, and I've been ripping some disks for archival purposes (some 3.5", some 5.25"). It spits out .IMD files, which contain some amount of header and metadata, ...

I'm trying to identify a game I remember from my first exposure to computers (the Apple II at secondary school back in the late '70s). I remember two games I really enjoyed, the first a Star-Trek-...

Recently, Microsoft published the source code of old MS-DOS versions on GitHub. What is odd in my opinion is the use of x86 assembly language for everything. The assembly language would not be my ...

I have an Indy running on IRIX 6.5. The main web browser cannot run very many websites. Are there any other more modern browsers that I can use to run websites such as wayback machine? When I try to ...

I was reading on this page about the Final Fantasy demo cartridge, and I wondered why more cartridge games didn't have demos. From this wiki page: The availability of demos varies between formats....

Basically any computers from the mid 90s and earlier perform a slow memory check on every single boot. The more memory there is present, the slower that process becomes, for example: https://www....

I'm building a FDD controller out of a $10 microcontroller. It's mostly working pretty well, and I can read both 720kB and 1440kB PC MFM disks (the only ones I have to test with). However... if I ...

Have video game developers blocked the ability of GameShark to find unused content in games (that they either didn't have time to remove unused, or plan to use in an updated version or sequel) I ...

I have several retro machines and add-on cards for the Amiga that use ZIP RAM. This vertically mounted chip design enjoyed a brief popularity in the early 1990s, in between the original DIP DRAM and ...

How did the vendors using copy protection create weak bits on the floppies? This always fascinated me as a kid. I ended up finding a weak bit emulator that would intercept the floppy disk interrupt ...

I'm building myself a floppy disk interface based on a microcontroller. I'm successfully reading the bitstream off the disk and (probably) decoding the MFM bitstream into actual bits, based on the ...

I'm trying to emulate programs from the 80s, but with an accurate clock-speed¹ (pretending its an 8086). Meaning that if a 8086 would take X ms/opcode, the emulator should take X ms (+- a bit of ...

From what I read, most line printers have 132 columns. Also, the VT-220 and presumably other terminals may be switched between 80 columns (that's a usual width) and 132 columns. As I recall, 80 ...

I was just What is linux-gate.so.1?, and it says this Intel recognized this problem early on and introduced a more efficient system call interface in the form of sysenter and sysexit instructions. ...

Whilst working on a personal project, I discovered the existence of an old version of the XSLT specification, identified by the namespace http://www.w3.org/TR/WD-xsl instead of the modern https://www....

We all know that "640K should be enough for everyone". But who actually set this limit? The quote is often attributed to Bill Gates, but it doesn't seem like a decision for an Operating System vendor ...

Considering all those early home computers, the ZX Spectrum, the Galaksija, the VIC-20, the Apple I/II/III, and all of those, they all have some 8-bit CPU which does integer arithmetic and no floating ...

In the last century, a brand of video cards that rhymed with quality, Matrox, was very popular and the choice for professional applications and to some extent for 3D gaming. The benefits of upgrading ...

I have this beast, the Canon X-07: The product by itself was of high quality, Z80 and RS-232 compatible and with a lot of peripherals available such as: thermal printer 4 colors tracer infrared ...

I know from this answer that, Modern x86 CPUs are binary compatible with 8086. You can literally run 8086 binaries on a modern PC, in real mode. (The species analogy is a stretch here, but works ...

The title pretty much says it all. I'm looking for information about an operating system called I/OS by a company called Infosoft in the early 1980's. I think it might have been a CP/M variant and ...

The Z80 has the surprising feature of a second set of registers. I suppose these were intended to be used for rapid task switching or interrupt handling, though I think if I were programming a Z80 ...

TL;DR: With what values are the I/O port registers (locations $00 and $01) on the 6510 initialised when it is powered on? I'm writing a Commodore 64 emulation. The Commodore 64 uses a 6510 ...

I read in some forums that some 286 boards support UMBs and thus can load drivers and TSRs into the upper 384 KiB of conventional memory. What chipsets support this and do I need special drivers?

I have a Panasonic "Penwriter" model RK-P400C electronic typewriter/plotter from circa 1985 I'd like to be able to connect to a modern PC. And hopefully even use to draw graphics! Bought in almost new ...

The Z80 indirect I/O instructions are a little quirky: the instructions with the standard mnemonic in r, (c) (where r is a stand-in for any of the normal registers) actually puts the register pair bc ...

I was reading an Wikipedia article named "History Of Microsoft Flight Simulator" and I noticed something weird about Microsoft Flight Simulator 1.0: November 1982 sometime during 1981-82 ...

How do I compile my code that I have typed on my SGI Indy computer? I have already tried to install the GCC/G++ compilers, but when I run my application, I get the error that says: gcc: ...

The bi-directional 8-bit data bus of the Intel 8080 was split into two unidirectional 8-bit data buses. Later these two 8-bit busses would be combined to support a 16-bit data width for more advanced ...

S-100 was, as I understand, a very popular way to connect various computer equipment together in the past. Also, from what I understand, S-100 closely matches the same signals as the Intel 8080, as ...

I tried to install GCC on Irix, but it did not work. I tried to install Code::Blocks on Irix, and it did not work. The GCC gave me parse errors in iostream.h and streambuf.h, and NetScape does not ...