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1500 questions
16
votes
1 answer
Why does the Z80 not have EX DE, IX?
Reading Decoding Z80 Opcodes, There's a section about the 0xDD prefix. This instruction prefix causes the next instruction to use the IX register instead of the HL register. That makes sense. HL and IX (also IY) are designed for holding pointers.…
Omar and Lorraine
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16
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9 answers
Besides the VIC-20 did any other micros have fewer than 32 columns available for text mode?
On early microcomputers it was common to have 40 columns of text with the alternative usually being 32 or 64 for technical reasons as well as ambitious 80 column models that became more common as technology improved and prices for memory and…
David
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16
votes
2 answers
How to transfer file(s) between modern Linux host and HP48 handheld calculator?
Context at the time
Handheld graphing calculator HP 48 series - Wikipedia, produced between 1990 and 2003, include infrared and serial communication ports to send and receive data and programs between each other and computers using the Kermit…
Stéphane Gourichon
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16
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3 answers
Why is the Unix epoch January 1st 1970?
In honor of this weekend being 1,600,000,000 (1.6 billion) seconds since the Unix epoch, I was wondering if anyone knows why January 1st 1970 was chosen?
According to Wikipedia,
The earliest versions of Unix time had a 32-bit integer incrementing…
Captain Man
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16
votes
2 answers
When did FORTRAN decide on signed integers?
I have personally always been of the opinion that it would make sense for the default integer type to be unsigned, though it's been a long time since that would've been a live issue for debate; C in the 1970s was already defaulting to signed…
rwallace
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16
votes
1 answer
What does the H protection bit mean under classic AmigaOS?
The AmigaOS file protection bits allows for Read, Write, eXecute, Delete permissions on files, similarly to Unix (save for the Delete permission). Additional bits are Archive (reset when a file is written), Pure (signals that the program code is…
user180940
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16
votes
2 answers
Why would installing Windows 9x on a Sager NP8200 or Wedge 466/DX2 laptop brick the system?
In the setup.txt file on the Windows 95 and 98 CDs (located in the \WIN95 [Windows 95] / \win98 [Windows 98] folder), which contains important information on setting up Windows and solving or working around problems that can occur thereduring, there…
Vikki
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16
votes
1 answer
Why did some MOS 6502 packages have holes in them?
Someone was recently selling an early MOS 6502 CPU on Ebay (date code 0277) in a ceramic package that had a couple of holes in it. You can see them clearly (under the tape, which presumably was not applied by MOS) in this image:
Another chip I've…
cjs
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16
votes
2 answers
How was a line of Commodore 64 BASIC code stored in its memory?
I am reading up on old C64 stuff and I am using the Vice emulator to play with it. Currently I am studying about how the C64 stored BASIC programs in RAM.
This is quite clear (it starts on address $0800 and goes from there, etc) and the Vice monitor…
Bart Friederichs
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16
votes
12 answers
How can a Z80 assembly program find out its own memory address?
I'm wondering how to write a program in Z80 assembler that discovers its own memory location.
I thought that maybe I could somehow load the program counter PC into, for example, BC.
Is there a way of doing this?
I'm messing with a single board Z80…
twisted
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16
votes
4 answers
Why did 1-bit DRAM chips have separate data input and output?
Many 1-bit DRAM chips provide two pins for data communication, one for writing data (typically described as Din or D on datasheets) and one for reading data (Dout or Q). Examples I've found include the 2118, 4164, 41256, 4532, 4816, and 4116…
Kaz
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16
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1 answer
Can I use all features of a Commodore 1571 external drive from a C64?
I know that the Commodore 1571 drive works perfectly well with a C64, since the 1571 will detect it is connected to a C64, and will enter 1541 emulation mode. After which, the 1571 just behaves as a 1541.
BUT, the 1571 is a much more capable drive.…
Brian H
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16
votes
5 answers
Why isn't the WDC 65816 available in "externally" 16-bit versions?
Actually, unless there are actual design notes from WDC available, the
question is really one too long for the title field: "What, precisely,
are the disadvantages of having a version of the WDC 65816 with a
16-bit data bus and/or non-multiplexed…
cjs
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16
votes
4 answers
Why are old computers so vulnerable to temperature changes and moisture?
Interesting discussion by someone thinking of procuring a PDP-11/34, though having difficulty finding suitable space for it: https://www.reddit.com/r/retrobattlestations/comments/dztvci/minimum_viable_system_for_pdp11/
A comment that caught my…
rwallace
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16
votes
4 answers
Is there any way today to recover/dump 2M disks?
2M disks where formatted using 2MGUI to increase 3"1/2 & 5"1/4 DD/HD/ED disks' capacity.
Is there any way today to recover/dump these disks to a file with modern hardware? Specially the 5"1/4 ones...
I've got both kind of floppy drives but not…
NataliaPC
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