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.
In general: there were some system variables, system stack, display memory, buffers, etc. On some systems, there was a RAM area "under" the ROM (it means on the same address, but not accessible in a straight way) - for example, the Atari XL.
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.
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 ...
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.
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 ...
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 ...
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 (...
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 (...
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 ...
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.
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 ...
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, ...
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 ...
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
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.
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 ...
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 ...
Computer "Composit" (Leningrad+).
Left to right:
+5V 0.6 Ampers
+5 Volts, 1 Amper
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 ...
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, ...
The ST-238R shown in the image is an RLL (Run Length Limited) drive and will not work correctly with a standard MFM controller, although it has the same ST506 electrical interface and cabling. To read back your data, you will need an RLL controller, which unfortunately are less common than MFM controllers and might not be easy to find.
RLL is an encoding ...
The fact that there are two edge-connectors on the drive tells me that this drive uses the MFM or ST506/ST412 interface (or related interfaces such as RLL or ESDI). These were used on the earliest of PCs and compatibles, as well as other computer systems of the 1980s. This predates the use of SCSI and IDE (ATA) hard drive interfaces that were common from the ...
The 6502 is one of the few CPUs without build in capabilities to share the bus (*1,2). It always drives the bus. Any sharing will need external logic to detach the CPU and let others drive the bus (see CMOS Enhancements below as well).
Full bus access can be gained (*3) by waiting for any non write cycle (R/W = high during PHI2 = high) and halting the CPU ...
The 6502 drives the address bus full-time, but the "Phi2 low" or "Phi1" phase of the bus can be (and often was) used for non-CPU data transfers without interfering with the CPU's performance. Most often the Phi1 phase was simply dedicated to video display reads, with the side-effect of performing DRAM refresh cycles.
If your system design includes this ...