Most Popular
1500 questions
39
votes
2 answers
Can a USR command damage a ZX Spectrum?
I recently came across this magazine snippet; specifically this section:
Aprovechamos para avisar a los usuarios del Inves, que nos ha Ilegado el rumor de que haciendo:
BORDER 5
RANDOMIZE USR 4665
se averia el ordenador. No hemos tenido aún…
wizzwizz4
- 18,543
- 10
- 78
- 144
39
votes
11 answers
What's the origin of terminating strings by setting the high bit of the last character?
I was looking at a hex dump of the ROM BASIC from the original IBM PC and found some byte strings like this (ASCII dump is on the right):
50 52 49 4e d4 9d 4c 49 53 d4 9e 50 4f d3 1b 45 PRIN..LIS..PO..E
With a closer look, I saw that 50 52 49 4e…
user22483
- 383
- 3
- 5
39
votes
1 answer
How did voice dialing work in old Nokia phones?
For example on S40 or the 3310, users were able to set voice tags (also known as voice commands) for contacts. The phone could then recognize the command later and dial the right number.
With neural networks and much faster computers, this is not…
Luc
- 423
- 4
- 7
39
votes
1 answer
What was "the shrinkwrap issue?"
I first read "Alice in UNIX Land" (by Lincoln Spector, Texas Computer Currents, Sept. 1989), probably around the time when it was written — and at that time didn't understand very many of the jokes. Having gradually gained some experience (or at…
StayOnTarget
- 3,856
- 1
- 24
- 41
39
votes
4 answers
What was the design rationale behind multi-port and multiple connections (and back-connections) designs of the early protocols like NFS or FTP?
Originally, the FTP protocol connected back from the server to a client to actually transfer files through that new connections. 14 years later after the introduction of the FTP, the 'passive mode' was added to it, so that only client connects to…
lvd
- 10,382
- 24
- 62
39
votes
5 answers
Apocryphal (?) tale of hard drive platter propelled through a wall?
In the mid-1990s while a student at a US university during a computer science lecture, my professor (not a TA or grad student) told us a story of "witnessing" a large, then old-fashioned metal hard disk platter somehow breaking free of its mounting…
StayOnTarget
- 3,856
- 1
- 24
- 41
39
votes
1 answer
Z80 CPU address lines not stable
I just got a Z84C0020PEC and wired it up to test it, using this circuit:
Except that I've added LEDs to A0 through A9. It appears that A0 through A6 operate correctly, but A7 though A9 (I've not tested the rest of the upper bits) are only active…
Mike
- 493
- 4
- 5
39
votes
4 answers
When did computers stop checking memory on boot?
I remember my old 8088 used to do this (640K OK) but can't remember seeing anything like this since. Does this still happen and it's just not visible? If not, when did it stop, and why? (Imagining it might take too long with today's memory and/or…
dashnick
- 1,258
- 12
- 17
39
votes
3 answers
Why did the VIC-II and SID use 6 µm technology in the era of 3 µm and 1.5 µm?
In short, 3 µm looks like it was the "standard" process size at the time, and it was available to Commodore before the chips were designed. Therefore it looks like using the larger 5 to 7 µm process nodes was a deliberate choice in designing these…
supernoob5000
- 719
- 6
- 9
39
votes
8 answers
Why did computer video outputs go from digital to analog, then back to digital?
While early microcomputers used analog video outputs (often to use a television as a display), higher end machines such as the BBC Micro or Commodore 128 supported a digital RGB (or RGBI) video output. In the IBM-compatible world, the CGA and EGA…
Kaz
- 8,086
- 2
- 38
- 81
39
votes
1 answer
Fixing obscure 8080 emulator bug?
I'm using cpudiag.bin from http://www.emulator101.com/files/cpudiag.bin to test my emulator. I've already implemented the CP/M CALL function at 0x05, offset the program at 0x100 and fixed the offset at byte 112 + 0x100, as per this site:…
dav
- 1,059
- 1
- 10
- 16
38
votes
2 answers
Can an x86 CPU running in real mode be considered to be basically an 8086 CPU?
When an x86 CPU is running in real mode, can it be considered to be basically an 8086 CPU (or maybe 8088)? Or are there differences between the two?
user12245
- 381
- 3
- 3
38
votes
1 answer
How did the 8086 interface with the 8087 FPU coprocessor?
The 8087 has many instructions - too many, it seems, to be encoded as part of the 8086 instruction set. How did the Intel 8086 interface with an Intel 8087 FPU that a user added?
Consider the following x86 assembly code sample:
// c = a + b;
fld …
Jet Blue
- 1,995
- 3
- 18
- 25
38
votes
4 answers
History of Ctrl-S and Ctrl-Q for flow control
Which OS was the first to use Ctrl-S and Ctrl-Q on the console for pause and continue?
I first discovered Ctrl-S in IBM PC DOS 1.1.
Old Geezer
- 483
- 1
- 4
- 6
38
votes
3 answers
What was the point of Apple Pascal having its own file system?
Apple's UCSD Pascal for the Apple II used its own file system rather than the existing DOS 3.3 of the day. I'm not sure if it overlapped SOS at all, but regardless of timelines it seems that the Pascal file system was separate and incompatible from…
bjb
- 16,259
- 46
- 141