23

If you watch enough YouTube videos of repairing old micros — and even ones that aren't that old (486s didn't come out that long ago, did they?) — you'll see a lot that have suffered some sort of damage due to storage over the years. Some damage, such as corrosion due to battery leakage or cracked circuit boards, is not due to climate. However ...


10

Yes, for the IBM 360/30 at least the 16 32-bit registers (and 4 64-bit floating-point registers) were stored in the same core memory as the main memory. The IBM 360/30 used the IBM 2030 Processing Unit as it's CPU, and the IBM 2030 Processing Unit Field Theory of Operation manual states on the page 1-4 that "The sixteen general registers and the four ...


10

Since I know that little machine quite OK I think I'll throw my 2 cents. When the ZX81 came out it was advertised with a character based screen of 24 lines by 32 characters, each 8x8 pixels in black and white. Of these 24 lines only 22 lines are available for user programs per default. The system variable to change this setting was documented, though. Its ...


6

The Commodore 64 advertises 38911 bytes free for BASIC upon startup. It's a 64kb machine. Non-BASIC programs could use the full 64kb rather than the ~38kb. Therefore using more memory than is available to BASIC was routine. The difference was primarily that BASIC and the rest of the kernel don't need to be present, so if you're not using them then you can ...


5

Caviar, as a word, is associated directly with luxury. That's most likely what the marketing focus group were thinking when they put it forward as a possibility. Most likely only one possibility of several, which were then selected by C-level executives. Relatively few people know what the eggs actually taste like.


5

Is there something about the technology with which the older minicomputers were built, that makes them more susceptible to moisture damage? No, it's about any human made - in fact even any pysical item at all. I've been working with personal computers of various kinds for going on four decades, and I have never seen hardware rendered inoperable just by ...


5

Computer "Composit" (Leningrad+). http://sblive.narod.ru/ZX-Spectrum/Composite/Composite.htm http://sblive.narod.ru/ZX-Spectrum/Composite/CompositeSCH-MONT.gif Left to right: KEMPSTON Right Left Down Up Attack/Fire Common TAPE Input Ground Out TV Red Green Audio Out Blue Video Out Ground +5V 0.6 Ampers +5 Volts, 1 Amper Ground Ground Ground ...


4

If by "unavailable to store BASIC program text," the general answer would be "all sorts of stuff." A typical memory map for an early Apple system would be along the lines of the following: $0000 - $00FF (0 - 255): Zero Page (system variables) $0100 - $01FF (256 - 511): 6502 Processor Stack $0200 - $02FF (512 - 767): GETLN Line Input Buffer $0300 - $03CF (...


4

Let's take for example an MSX computer with 64K RAM. That's what you get on boot: Where does this 28815 come from? To start with, a MSX is a Z80 based machine. The Z80 has an addressing space of 64K. The MSX standard divides these 64K in four 16K pages that can be independently switched to any internal or external memory slot. When booting in BASIC mode (...


4

Did any 360-compatible machine ever actually implement its registers with magnetic cores? Yes, of course, in fact, it was standard for low end machines. Beside IBM, as Ross Ridge details, many early compatible manufacturers did so. Examples are Sperry's Univac 9000 series, RCA's low end Spectra 70 models 15 and 25, or Siemens 4004/15.


3

On ZX Spectrum there where these approaches I know of: using Border area the border has single color but by fast alternating it (in respect to CRT electron beam position) it can be used for rendering. Demos and even some games used it for printing some text or stuff. IIRC there was one flight simulator that used it to show the horizon cant remember its ...


3

Answers for the Apple II: (Please have a look at this answer to understand the memory layout, and where the areas used by BASIC are placed). 1) Were there any games/software that used memory beyond what was advertised as available to BASIC on the machine? Assuming that "advertised as available to BASIC" means "between $801 and DOS", then yes, machine ...


3

Someone can correct me if I am wrong, but I think larger components/contacts create larger shear forces due to the different rates of thermal expansion in different materials. For instance, a tiny solder joint will have a much smaller difference between the expansion of the solder and of the plastic.


2

The specifications for most computers include (or used to) prohibition of 'condensing moisture' conditions. The 'condensing moisture' means dew. On a ship, below waterline, if there's no air conditioning, you'd violate that condition. The reason is that the electronic parts of a computer have multiple different small metal parts. Adjacent dissimilar ...


2

One other thing to consider, in addition to having the correct interface, is whether the electronics are damaged in some way as to cause the drive to overheat. I've had some success in the past pulling data from "dead" drives by putting them in a refrigerator or freezer and cooling them down to the point where it's possible to get (some) data off the drive ...


2

For nearly all machines with BASIC, I would expect any non-BASIC programs to use BASIC's workspace. Also, people (inc me) would not allow the OS to get a look-in and use its memory too ;)


2

On the VIC-20, you only had character mode (22x23) but you could redefine the character set, allowing 128x128 I think (may have been less) or what looked like more if you repeated characters around the screen. The BBC Micro had a 6845 CRTC which allowed very flexible displays and you could display 640x512i (although as this used 40K of the available 32K, ...


1

For standard displays the Atari ST purports to offer at most a 640x200 pixel resolution, with a classic '80s big old border around the display. In PAL world the border is about 36% of the vertical time, which is conservatively at least 20% of the visible area, and 37.5% (/~22%) of the horizontal. Clever programming allowed Atari ST programmers to remove the ...


1

There are a lot of easy and simple constructions, based on the Z80 CPU. I prefer the simple Grant Searle's Computer. If you prefer the more simple way, you could try the ready-made solution, like the RC2014 Homebrew Computer.


1

There was a simpler but much more expensive solution used in the 1981 BBC Micro, it used 4MHz RAM and a 2MHz 6502A and let the 6845/VideoULA have the other 2MHz (every other 4MHz cycle). There is a modern blitter for the BBC Micro, but it wouldn't have been available BITD. https://stardot.org.uk/forums/viewtopic.php?t=14125


1

For the Librascope/Royal Precision/General Precision computers, i.e. the LGP-30 and its little and big brothers (LGP-21 and RPC-4000), the actual data transmission is 6 bit parallel. Two sets of 6 data lines, to and from the Flexowriter respectively. This is complemented by a handful of handshake and sync signals, to indicate that characters are available, ...


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