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17 votes
1 answer
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Why is the Apple II hi-res HGR command so slow?

The Apple II hi-res screen sits on 8KB of memory, so it should be possible to erase it quickly. The Applesoft HGR command is slow enough that the "Venetian blind" erasure is clearly visible. ...
fadden's user avatar
  • 9,060
36 votes
6 answers
4k views

Why did the Bell 103 modem use a data rate of 300 bps?

Virtually every telephone modem in existence runs at a data rate that's a multiple of the Bell 103A's 300 bps. Why was the base 300 bps chosen in the first place?
Mark's user avatar
  • 8,657
5 votes
1 answer
154 views

Extended Color BASIC TIMER Function

How does the TIMER function work in Extended Color BASIC? How does the number keep incrementing even when the computer appears to be doing nothing?
tlindner's user avatar
  • 2,367
33 votes
1 answer
4k views

How does the command.com shell work with MS-DOS?

On my systems that are running MS-DOS, I change the default command.com to 4DOS for more features. How was the shell system designed and how did it with the operating system in MS-DOS that it enabled ...
Thraka's user avatar
  • 2,913
12 votes
2 answers
888 views

What did disk-validator do?

...besides relabelling the disk to 'Lazarus' and helping the Saddam virus spread? I know it was supposed to 'fix' corrupted disks that were ejected during a write operation. I don't think I've seen a ...
SF.'s user avatar
  • 7,115
10 votes
2 answers
577 views

Acorn Electron fails to load .UEF files converted to .WAV

I have an Acorn Electron that came without tape recorder, so I'm using Audacity to record and replay programs which works fine. Now I also have some software as UEF (Universal Emulator Format) files. ...
Cees Meijer's user avatar
12 votes
1 answer
248 views

Is my Atari Falcon's filesystem messed up?

I use the Cecile driver for the Kingspec DOM (basically an IDE flash drive0 in my Atari Falcon. I've noticed on occasion that in file dialog boxes (save, open etc.) I sometimes see weird files, called ...
Matt Lacey's user avatar
  • 2,320
19 votes
1 answer
901 views

How did XBAND modems transmit game state?

The XBAND Video Game Modem and Network allowed owners of Sega Genesis and Super Nintendo game systems to play head-to-head over a phone line in 1994, before "twitch" gaming over the Internet was ...
fadden's user avatar
  • 9,060
10 votes
2 answers
443 views

How to bring up the firmware console on a SunBlade 100

I've got an old SunBlade 100 workstation that I'm trying to install OpenBSD on. The first step in the process is to bring up the OpenFirmware prompt to select the boot medium, which you do by ...
Mark's user avatar
  • 8,657
19 votes
2 answers
877 views

Atari 2600 paddle controllers slow, jittery

I recently picked up a pair of Atari 2600 paddle controllers for use with my Atari Flashback 6. The Amazon store said in the product description that they had been "tested." However, they are barely ...
Aaron's user avatar
  • 2,384
16 votes
4 answers
506 views

What was the first intentional malware that got spread over multiple machines?

I would like to know which program can be seen as the first malware. To define the term "malware" in this question, I would suggest those criteria, but you may modify them if you feel the need: real ...
Byte Commander's user avatar
13 votes
1 answer
672 views

What does Personal Paint documentation actually refer to by "unmaskable interrupt" for its "crash protection feature"?

Personal Paint was a gfx program for Amiga that introduced many novel concepts, some quite ingenious, some... controversial. Among all, it had a "crash protection" feature, that was meant to enable ...
SF.'s user avatar
  • 7,115
24 votes
3 answers
1k views

How can you measure time using BASIC on Atari XL computers?

Some time ago, I benchmarked some 8-bit computers to find out the fastest BASIC interpreter. I ended up using the classic SAXPY benchmark, as I didn't want any I/O overhead to fool the measurement: ...
mcleod_ideafix's user avatar
20 votes
1 answer
1k views

What did the cassette bootloader in 8 Bit Ataris do?

...or for that matter, what didn't it do, so that you'd use the "bootloader/main program" separation instead of loading everything at once. Normally, when loading games or any non-BASIC software from ...
SF.'s user avatar
  • 7,115
22 votes
4 answers
2k views

How did programs/patches stopping Amiga idle floppy drive noise work?

The Amiga computers would by default automatically detect a disk being inserted and respond by reading from it and displaying its icon. Polling the drive(s) for a new disk would produce a clicking ...
nsandersen's user avatar
  • 1,753
15 votes
3 answers
1k views

Atari 800XL showing a red screen

My friend has a Atari 800XL in mint condition. When the device was turned on, the only thing that appeared was a dark red screen. Another friend of mine figured that the memory chips were to blame, ...
Anthony Pham's user avatar
  • 2,474
17 votes
4 answers
4k views

Booting an Amiga 1000 directly to the hard drive without Kickstart floppy

The Amiga computers such as the Amiga 1000 required a Kickstart floppy to be able to boot directly into a hard drive. I have a Amiga 1000 as well but missing the Kickstart floppy. I would like to ...
Anthony Pham's user avatar
  • 2,474
3 votes
1 answer
706 views

Why won't the game "Ultima I" work on my Apple IIe system? [closed]

I'm trying to complete the original Ultima I on an Apple //e. These instructions explain space flight, but I can't seem to destroy enemy ships in order to become a Space Ace, even when I should be ...
Nick Westgate's user avatar
19 votes
2 answers
839 views

What are the common sources of incompatibility on different MSX computers?

I remember that a LOT of games for my MSX (I live in Brazil) don't work without some modification. For example, several need some kind of tweak on the loader, like poke -1,0. I would like to know ...
flavio's user avatar
  • 580
15 votes
2 answers
1k views

What information is encoded in the 22-digit barcodes on the Amiga's case?

What information is encoded in Amiga's 22-digit barcodes? For example: 0103791363642010121234
snips-n-snails's user avatar
17 votes
2 answers
2k views

Comprehensive test suites for MOS 6520 PIA / 6522 VIA / 6526 CIA

Are there any automated test suites for MOS 6520, 6522 and 6526 chips? I am looking for test suites aimed at making sure datasheet-based independent reimplementations of the above chips (e.g. FPGAs or ...
Cactus's user avatar
  • 2,760
19 votes
1 answer
6k views

Is it possible to use an Amstrad CPC464 with a modern monitor or TV

During a recent move I lost the monitor for my Amstrad CPC464. Is it possible to adapt the output of this to work on a modern monitor or on television set?
404 User not found's user avatar
31 votes
5 answers
6k views

What were the differences in floppy disk formats between Amiga and IBM/PC compatible computers?

The capacity in Amiga Old File System format (OFS, OS version 1.x) was 840KB, with the Fast File System ("FFS" (!)) introduced for OS 2.x onwards able to store 880KB. The PC format stored 720KB on the ...
nsandersen's user avatar
  • 1,753
16 votes
2 answers
587 views

Inserting NOPs to improve IIgs shadow copy performance

The answer to this question discussed a technique on the Apple IIgs for copying memory onto itself. The motivation for the technique was to maximize use of "fast" (2.8MHz) RAM over "slow" (1MHz) RAM ...
fadden's user avatar
  • 9,060
24 votes
5 answers
3k views

How much benefit should be expected on a more advanced compiler for z80/r800 based computers?

I am self studying about compilers, and get hands on very good textbooks about the subject. I am thinking in develop a compiler using the almighty llvm infrastructure to cross compile to old computers,...
flavio's user avatar
  • 580
41 votes
3 answers
6k views

80286 can switch from real mode to protected mode - but why not back?

It's been a while, but I've read in a system programming book that you could switch your Intel 80286 CPU from the normal real mode to a more powerful protected mode. I clearly remember that they said ...
Byte Commander's user avatar
14 votes
3 answers
2k views

What format is the (Timex) Sinclair ZX Spectrum SCREEN$/.SCR file

What format is the (Timex) Sinclair ZX Spectrum SCREEN$/.SCR file and how is the fore/background and attribute data encoded within this format?
John Parker's user avatar
26 votes
3 answers
4k views

Linux 68k Macintosh emulator

I'm currently using the absolutely ancient "Fusion" emulator to emulate a 68k Macintosh (specifically, a Quadra 700), but it only runs under MS-DOS, so I'm using a VirtualBox VM to emulate that. I'd ...
Mark's user avatar
  • 8,657
17 votes
1 answer
906 views

How can I interface with an old Atari from a modern computer?

I have an old 8bit Atari at my dad's house which would be fun to play with. It has a keyboard, computer and screen, turn it on, and program BASIC. But I'll possibly want to load the code from a ...
dwjohnston's user avatar
21 votes
2 answers
2k views

What size screws were used in the Amiga desktop cases?

On the Amiga 500, 500+, 600, and 1200, what size screws were used to hold the chassis together? Is it the same size screw for all, different screws per machine, different screws front and rear, or ...
snips-n-snails's user avatar
6 votes
2 answers
427 views

How do I interpret the old Mac character set?

Older Macintoshes and the Apple IIgs used a custom character set for documents and filenames. Each character was held in an 8-bit byte, using 0x00-0x7F for ASCII, and 0x80-0xFF for various symbols ...
fadden's user avatar
  • 9,060
17 votes
3 answers
2k views

Atari 800 CPU - 6502 vs. Sally

Regarding the Atari 800... What's the difference between the 6502A and the 'Sally'? Is it simply a revision, or do the changes improve performance?
Brian Blake's user avatar
  • 1,731
22 votes
5 answers
6k views

How can I power a C64?

I was chatting with our neighbor and after some long talking, I found out that he has a Commodore 64. I'd love to test it, however I'm not sure how to power it. How can I power a C64?
ave's user avatar
  • 860
50 votes
11 answers
13k views

What is the oldest computer capable of running a modern version of GNU/Linux?

A bit of a trivia question: What is the oldest hardware capable of running a modern Linux-based operating system, including user-space? (Not necessarily GNU userspace, but running a standard GNU/Linux ...
Jonas Czech's user avatar
8 votes
3 answers
1k views

What are the options for installing a 6309 in a TRS-80/Tandy Color Computer

The Hitachi 6309E CPU is a direct replacement for the 6809E in the CoCo. What are the options to upgrade to this processor?
Brian Blake's user avatar
  • 1,731
11 votes
1 answer
482 views

Differences in disk storage between systems

Coming from the TRS-80/TandyColor Computer lines, I had always heard of how slow some other systems disk storage were, regarding data transfer rates, etc... The CoCo lines disk storage was pretty fast ...
Brian Blake's user avatar
  • 1,731
13 votes
2 answers
2k views

Expansion port on the Color Computer

The Color Computer has an expansion port. What is the pin out? What are the kinds of devices that can be used with it? How was the Multi-Pak involved?
tlindner's user avatar
  • 2,367
14 votes
3 answers
2k views

How do I connect a modern display, keyboard, and mouse to a Power Macintosh 6100?

I recently got a Apple Power Macintosh 6100 for free. It powers up and seems to work, so I want to try it out and see what it's like. Unfortunately, the important ports and connectors are "non-...
Jonas Czech's user avatar
49 votes
4 answers
5k views

Why do older computer cases turn yellow?

Why do plastic cases of old computers turn yellow? Is this yellowing a problem that has been solved in modern plastics?
CommonerG's user avatar
  • 713
12 votes
3 answers
2k views

How should I clean the plastic exterior of my computers and parts?

What is the most effective way to clean cases, keyboards, old calculators, etc. without harming or discoloring plastic finishes or printing/paint?
CommonerG's user avatar
  • 713
8 votes
2 answers
564 views

Toshiba T2000SX can't boot from non-original HDD - "02" all over the screen

I used to have an old Toshiba T2000SX laptop, but some day its HDD died. I found a newer laptop HDD that fit in and I could format it to appear to have a small enough capacity to get detected by the ...
Byte Commander's user avatar
13 votes
1 answer
913 views

What was the difference between CLOAD and LOAD "C:"?

8-bit Atari Basic had three different formats of storing programs on tape. CLOAD/CSAVE LOAD "C:"/SAVE "C:" ENTER "C:"/LIST "C:" I understand the specifics of the last one - it behaved as if the ...
SF.'s user avatar
  • 7,115
15 votes
1 answer
746 views

How does one convert Atari assembly to A=USR(ADR("[garble]")) style BASIC wrapper?

Some small utilities, tools etc for Atari were distributed as BASIC programs that would consist of just one line, that looked something like this: 10 A=USR(ADR("p$PHHLéúÿÿÇEéúÿÿ@éüÿÿ2A$éòùÿÿE°U´è§...
SF.'s user avatar
  • 7,115
20 votes
2 answers
2k views

What was the earliest non-valve, non-mechanical computer?

Just wondering how history questions will fare here. They could be a good addition to our scope. Pretty much exactly as the title says. Some of the earliest computers were based on valve systems or ...
Åna's user avatar
  • 431
14 votes
3 answers
2k views

How did Atari cassette "turbo without hardware mods" work?

There were some cassette copying programs for 8-bit Atari, that boasted saving the games in a way that would load it at up to 1800baud - versus the standard 600baud, which was a significant ...
SF.'s user avatar
  • 7,115
12 votes
1 answer
507 views

How did the Lazer Systems Graphics Plus board work?

The first two Apple II models (the ][ and ][+) were unable to display lower case on the text screen. Some 3rd parties made lower-case adapters that replaced the character ROM (e.g. Dan Paymar's ...
fadden's user avatar
  • 9,060
27 votes
5 answers
4k views

Did any Amiga 500 games or programs (apart from paint programs) use more than 32 colours?

While the Original Chip Set (OCS) and Enhanced Chip Set (ECS) Amiga computers had the 32 x 2 colour EHB (Extra Half-Brite) and 4096 colour HAM (Hold And Mofify) screen modes, where these ever used ...
nsandersen's user avatar
  • 1,753
15 votes
1 answer
919 views

What format is used for CoCo cassette tapes?

Color Computer machines initially used audio cassette tapes for storage. How was the data stored? What was the maximum bit rate?
tlindner's user avatar
  • 2,367
7 votes
2 answers
422 views

What are these bus/tag connectors for?

I have a pair of connectors that mate with each other. One is labeled BUS, the other TAG. What are they for?
fadden's user avatar
  • 9,060
29 votes
2 answers
3k views

Why does 6502 indexed LDA take an extra cycle at page boundaries?

On the 6502 CPU, this instruction: LDA $0380,Y takes either 4 or 5 cycles, depending on whether the indexing crosses a page boundary. But this instruction: STA $0380,Y takes 5 cycles regardless ...
fadden's user avatar
  • 9,060

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