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1500 questions
48
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2 answers
Why does the 80486 take longer to execute simple instructions than complex ones?
The 80486 processor can execute many instructions in a single cycle, such as a register-to-register add instruction (ADD EAX, EBX, for example), which one would generally assume is fairly complex, requiring two registers to be read, a full 32 bit…
occipita
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47
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8 answers
Why were chips socketed in early computers?
In many early computers, many of the chips were in sockets rather than soldered directly to boards, e.g. this series of pictures of the Tandy CoCo 1 has a note to the effect that all the chips are socketed:…
rwallace
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47
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3 answers
What's the relationship between early 90s Pentium microprocessor and today's Intel designs?
My simplified understanding of the evolution of the Intel processors over the last 20 years is that the Pentium II and Pentium III architectures were sort of "dead-ends", and today's Intel processors were built on an earlier design introduced with…
Brian H
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47
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6 answers
What is a Dumb Terminal?
There seems to be some confusion what a 'Dumb' terminal is as visible in answers and comments to this question about portable dumb terminals. So:
What is a Dumb Terminal?
Points that would help to distinguish might be:
What features or missing…
Raffzahn
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47
votes
3 answers
What happened to the SEV instruction on the 6502?
The 6502 has a group of opcodes which copy bit 5 from the opcode into one of the status flags.
(I know it's not implemented this way, but it looks as though the bit fields are: 2 bits to select the flag out of CIVD, one bit to clear or set,…
Omar and Lorraine
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47
votes
3 answers
How did C64 games handle music during gameplay?
On the C64 there was no threading, so how did games handle treating at the same time music and game code? Music requires exact timings, and the SID had to be instructed to change the note at the right time. How did they achieve this? I suspect…
Stefano Borini
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47
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6 answers
Why does the 6502 have the BIT instruction?
The 6502 has a bit instruction which
copies two of the bits into the N and V flags,
pretends to and the byte with the accumulator, but discards the result and only affects Z.
I'm having a hard time picturing a use for this. And curiously, it's…
Omar and Lorraine
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47
votes
5 answers
Why are C64 games inconsistent with which joystick port they use?
The Commodore 64 has two DE-9 joystick ports. If I'm the only person that ever plays games on it, you would assume that you could just leave a joystick plugged into Port 1 and be done with it. However, there are a number of games out there which…
bjb
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46
votes
4 answers
Why would older video games include fragments of source code?
One thing that was surprisingly common in older video games (around the same era assembly language was king) was the inclusion of uncompiled, plaintext source code in the ROM. You can see many examples of this here.
My question is...why? It doesn't…
Mike Nielsen
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46
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2 answers
What computer system is this from 1984 Doctor Who?
In the 1980s, the popular BBC science fiction series Doctor Who used some real computer system(s) to display impressive (for the time, OK, maybe not!) graphics. They actually ran the software real-time and simply filmed the output on the…
CJ Dennis
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46
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1 answer
Which "very esoteric processor instructions" are used by OS/2?
According to the Oracle VirtualBox 6.0 manual, "Certain rare guest operating systems like OS/2 make use of very esoteric processor instructions that are not supported with our software virtualization. For virtual machines that are configured to…
TeaRex
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46
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4 answers
Commodore 64 to modern TV
I've been thinking about getting a Commodore 64 machine. However, I realise there's obviously no video cables I have that will work. But when I looked online there are many people using S-Video to VGA and stuff like that. My TV is quite old and has…
crabcrabcam
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46
votes
2 answers
Why are paddles called paddles?
A paddle is a sort of input device, common on early video game consoles and home computers, consisting of a handheld wheel with one or more fire buttons. Unlike dial boxes, which spin freely, paddles rotate through a fixed arc, with stops on each…
Psychonaut
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46
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2 answers
What did the DoD think Fortran lacked?
According to https://en.wikipedia.org/wiki/COBOL the project to design COBOL began when
On 28 and 29 May 1959 (exactly one year after the Zürich ALGOL 58 meeting), a meeting was held at the Pentagon to discuss the creation of a common programming…
rwallace
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46
votes
6 answers
How should we interpret Dave Cutler's criticism of Unix?
Dave Cutler is well known for his contributions to operating systems, having led the effort on VAX VMS at DEC and Windows NT at Microsoft. According to his Wikipedia page, he is also known for his attitudes toward Unix.
[Cutler] expressed his low…
Brian H
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