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Was the MC680x0's TAS instruction forbidden on Amiga systems only when operating in CHIP memory?
(Note: a previous version of this question asked about the CAS instruction, that was added by Motorola from the MC68020; the original one is the TAS instruction).
TAS is the acronym for Test And Set, an instruction that is used to create…
user180940
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24
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Was it possible programmatically to manipulate the volume as well as the pitch on computers with no sound chip?
On early versions of many 8-bit computers like the Apple II, Spectrum, and even the IBM PC, there was no sound hardware other than the simple "beeper".
Programmers made sound by hitting a hardware register that pulsed the beeper on and off.
You…
hippietrail
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24
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History of ARM Linux and FPA
ARM Linux, at least Debian was traditionally (pre eabi) built for the FPA floating point unit*. Unfortunately under old ABI it was not easily possible to mix soft-float code with FPA code. The result of this is that many arm Linux systems ended up…
Peter Green
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Why are branches relative in many 8-bit CPUs?
I was looking over an old article on the 6809 and was perusing the opcodes and noticed that the branch instructions came in two flavors, long and short. That sparked a memory about one of the 6502-series CPUs that added similar long-branches -…
Maury Markowitz
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24
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9 answers
Why does the single dot entry exist in file systems?
There is plenty of literature about its meaning, the current directory, but I would like to ask about why such thing do exist in first instance.
While CHDIR .. usefulness is obvious, i.e. go to the parent directory, CHDIR . is a bit confusing since…
Eric Cartman
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24
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8 answers
Why is the Intel 8086 CPU called a 16-bit CPU?
Based on my understanding, the bitness of a CPU specifies how much memory it can address (which is determined by the size of the CPU's address bus I guess). For example: a 32-bit CPU can address 232 bytes of memory.
But why is the Intel 8086 CPU…
user14660
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Why was hardware diversification an asset for the IBM PC ecosystem?
The IBM PC was cloned very early on, and many third parties made hardware peripherals. This required users to run an OS, install drivers, manage IRQs and hardware bus addresses, etc. Why was this a strength of the platform, instead of a…
nexus_2006
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How good was Woz's FP code?
I just came across this amazing 1976 article by Woz. In it he describes a relatively complete floating-point system for the 6502 with a 32-bit format (similar to earlier MS code).
I understand the code, mostly, but I am curious about its…
Maury Markowitz
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5 answers
How well known and how commonly used was Huffman coding in 1979?
Infocom's Z-Machine, designed in 1979, compresses text using a basic 5 bit code which is not very efficient in practice, achieving maybe a 1.5:1 compression ratio.
Huffman coding would be far more efficient, although more complex to decode, possibly…
curiousdannii
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Why did ScanDisk exist?
As far as I can tell, CHKDSK has been part of DOS and Windows since day one. However, in later versions of DOS, CHKDSK was shipped along side ScanDisk. As of Windows 98, running CHKDSK will result in the program printing a recommendation for…
TSJNachos117
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6 answers
How to use ISA card in modern PC
(Posted this on HW Rec but got no responses.)
Would like to use an ISA expansion card in a modern PC. There are
Expensive PCI - ISA adapters (but I cannot find any actually for sale now)
USB-ISA adapters, which may not work
New motherboards with…
Tomas By
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24
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3 answers
Documentation for the ZX Spectrum ULA
I am writing a Spectrum emulator, however I am finding it difficult to find official or reliable information about the ULA, its functioning and its pins.
Are there official sources documenting its inner workings?
Sklivvz
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Was Objective-C really a hindrance to Apple software development?
I have heard stories from some of the greybeards I have met on the Internet that Objective-C was by all accounts a nightmare to work with. Was that just a thing about all the low-level languages of its era or is there some sort of feature that made…
Neil Meyer
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23
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2 answers
What was the last x86 CPU that did not have the x87 floating-point unit built in?
This Wikipedia page says the following:
Most x86 processors since the Intel 80486 have had these x87
instructions implemented in the main CPU
So the above quote implies that some CPUs that were released after the Intel 80486 CPU did not have the…
user12280
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4 answers
What was the effect of the Video Game Crash of 1983 outside of North America?
The Video Game Crash of 1983 is well known for the effect that it had on the video game console market in North America. A prime example is Atari burying thousands of unsold game cartridges in landfill. However the effect on other global markets is…
Kaz
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