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35
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2 answers
What BBC Microcomputer features were requested specifically by BBC engineers?
When requirements for the BBC Microcomputer were developed as part of the BBC Computer Literacy Project, an outline specification was created by an independent consultant, the late John Coll. This specification was then fleshed out by the BBC and…
Mick
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Why does the GameBoy Pocket produce a blue line on power off?
Ever since I first had my GameBoy Pocket, I've noticed that the line drawn across the screen at power off (which I'm guessing is because the CPU has stopped sending clock signals to the display driver, and it's still pumping a little power into the…
jameswilddev
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What API did the "math box" provide?
Some classic vector arcade games, such as Battlezone and Red Baron, were based on the 6502 CPU. The processor wasn't fast enough to do the 3D computations, so a co-processor commonly known as the "math box" was used for vertex transformations.
How…
fadden
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How did Elite (BBC Micro) compress resources?
Elite, an Acornsoft game for the BBC Micro, is a game set in space.
Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is.
— Douglas Adams
There are a vast number of planets, resources, other ships...…
wizzwizz4
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What mid-1970s to mid-1980s home computers had their graphics characters added to Unicode 13?
The Unicode 13.0.0 release notes mention among the symbol additions:
214 graphic characters that provide compatibility with various home computers from the mid-1970s to the mid-1980s and with early teletext broadcasting standards
Which computers…
natevw
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4 answers
How much did IBM save by limiting the PC to 4.77 MHz?
My understanding is the CPU clock speed on the Intel 8088 in the IBM PC was selected as 4.77 MHz to simplify the design of the system. This despite the 8088 coming in two versions - 5 MHz and 8 MHz. Since later PC's routinely operated at higher…
Brian H
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Can the two CPUs in a Commodore 128 run at the same time?
The Commodore 128 has two CPUs. One is some variant of the 6502, and the other is a Z80.
One CPU is there for compatibility with the Commodore 64 and the other is there presumably to give basic compatibility with the CP/M titles that were…
Omar and Lorraine
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35
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5 answers
Why did Super-VGA offer the 5:4 1280×1024 resolution?
Before the age of LCDs, PC displays almost always targeted 4:3 CRT displays. And indeed, VGA and most super-VGA modes had 4:3 aspect ratio resulting in square pixels - except the odd 5:4 1280×1024 mode. This mode even caused 17″/19″ LCD monitors to…
Jonathan
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Why did connecting the IBM PC 3.5" FDD backwards cause the problems it did?
When the 3.5" FDD was introduced for the IBM PC and compatibles (or possibly earlier), someone made a decision to make the data cable between the controller and drive unkeyed. This, of course, meant that you could plug it in the wrong way if you…
user
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Are there vintage or historical bitmapped fonts available for non-commercial use?
I'm looking for a source for one or a few 1-bit black-or-white bitmapped fonts used in the past, available in a set of sizes.
Current incarnations might be available for large LED displays, but those may work best for point LEDs rather than square…
uhoh
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8 answers
How to put a delay in AUTOEXEC.BAT
I have this MS-DOS 6.22 machine which maps a network drive to a SAMBA share on a Raspberry PI. The PI is powered by a USB lead from the DOS machine, so the two power up together.
The mapping starts when this happens near the end of AUTOEXEC.BAT
net…
Rodney
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34
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1913 mystery computer below Grand Central Station
Over on the twobithistory Twitter channel, I came across this post from Gothamist about a computer from 1913 under Grand Central that was purportedly developed by Westinghouse.
According to the tour guide who was giving the talk,
Westinghouse in…
dashnick
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What are the registers W and Z inside a Z80?
Looking at the Z80's architecture diagram, there is the obvious register file in pink near the middle of the diagram. But four of those registers are not usable by programmers. Those are W, W', Z and Z'. So what operations did these registers…
Omar and Lorraine
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34
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5 answers
Why was nil defined as a reserved word in Pascal?
In Pascal, nil (the pointer value to "nothing") is a reserved word. Why wasn't it simply a predefined identifier as true and false are, for example?
This is stated in PASCAL User Manual and Report p. 109, as well in the ISO documents ISO 7185:1990…
JeanPierre
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How can you connect an Amiga 500/600/1000/2000 to a modern monitor?
I have an Amiga 500 that I'd like to get up and running again, but the 1084 monitor with which I used to use it has flyback transformer issues.
What options are available to hook it up to a modern display? From what I understand, adapting the…
Jim MacKenzie
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