Chenmunka
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6 answers
31 votes
4k views
Could you see what you are typing in a Teletype?
Accepted answer
51 votes

You could see what you were typing because it appeared on the paper in front of you. A teletype is just an electric typewriter at heart. There was no screen, the picture is just as the system was. ...

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3 answers
28 votes
5k views
Magnetic exposure to floppy disk damages file system and requires complete reformat?
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39 votes

A formatted disk contains markers which identify the start of each track and the start of each sector within the track. These markers are fixed magnetic sequences that are picked up by the drive ...

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3 answers
36 votes
5k views
What was the point of Apple Pascal having its own file system?
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37 votes

UCSD Pascal was a product of UCSD - The University of California at San Diego. It was not a product of Apple. UCSD Pascal was available on a number of machines, including the PDP-11, TI99/4, the BBC ...

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17 answers
22 votes
2k views
Was there a retro computer susceptible of being damaged only by issuing instructions at it?
28 votes

This was, and often still is, a deliberate design feature of safety critical computers. The Harmon VHLC, which is a 80186-based solid state interlocking used for railway signalling has been around ...

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1 answers
14 votes
788 views
How did the Sideways address space work?
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25 votes

Sideways ROM (also RAM in later models) was paged into the processor's address space. Sideways memory sat in the address range from $8000 to $BFFF. The BBC Model B had four slots on the motherboard ...

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5 answers
29 votes
5k views
How did the BBC Micro stay cool?
20 votes

The chips on the motherboard were quite widely spaced. This is still a design consideration when making boards more heat tolerant. Also, the chips didn't generate the sort of heat that more modern, ...

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3 answers
22 votes
2k views
What makes slot 7 of the Apple ][ unique from 1-6 and how was this used?
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20 votes

When the Apple ][ launched, it was marketed first in the USA. It was one of the first microcomputers to have built-in video circuitry for direct connection to a television monitor. The television ...

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3 answers
26 votes
2k views
What's the TUBE interface of the BBC micro all about?
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19 votes

The Tube interface was intended to enable the addition of what was known as a Second Processor. Although this was something of a misnomer as the additional processor became the main CPU of the system ...

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4 answers
7 votes
901 views
Identify an early 90s optical mouse
19 votes

Graphics digitisers like this were not optical, they were magnetic. The tablet contained a grid of wires which encoded a small magnetic signal. You moved either a stylus or, as you say, a device with ...

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2 answers
10 votes
980 views
How were Lisps usually implemented on architectures that has no stack or very small stacks?
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18 votes

You are misinterpreting the nature of the Lisp stack. The 256 byte hardware stack of the 6502 processor was not used for the large stacks required by Threaded Interpreted Languages (TILs) like Lisp ...

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3 answers
16 votes
1k views
Why did the Sinclair ZX-Spectrum use a membrane keyboard?
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16 votes

On the one hand it was clearly down to cost - being very much cheaper than a conventional keyboard. However, remember that the Spectrum was the replacement for the ZX81 and ZX80. These had ...

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4 answers
33 votes
10k views
History of Ctrl-S and Ctrl-Q for flow control
15 votes

It was nothing to do with an OS as such. Ctrl-S and Ctrl-Q are simply XON and XOFF in ASCII. These codes are used in serial communications to pause and resume sending. With hardware handshake on ...

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2 answers
13 votes
1k views
Heating issues in Apple II?
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15 votes

The Apple ][ could overheat if it had a number of cards installed. Especially if they were close together. So, yes, it affected (almost) all of them. This would affect the airflow within the case ...

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4 answers
14 votes
1k views
How can a computer use the drive's momentum for emergency power?
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15 votes

Any real attempt to use the momentum of the spinning disk to generate power would cause the disk to come to a halt very quickly. In essence, this is the principle behing regenerative braking of ...

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2 answers
12 votes
3k views
Found an IBM 5291. What is it, from when, and how much is it worth?
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14 votes

The IBM5291 is one of the IBM5250 series of terminals. It provides a user interface to an IBM minicomputer. The interface will be by Synchronous Data Link Control (SDLC). The hardware being ...

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3 answers
8 votes
468 views
Origin of dealer networks
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13 votes

You'd be surprised. There were specialist microcomputer shops in the late 1970s. I'm talking now about the UK and the shops that I used to visit. These were either individual shops or small chains, ...

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8 answers
43 votes
5k views
Executable ASCII files before x86?
12 votes

It was standard practice on the Sinclair ZX80 & ZX81 to put executable code into a REM statement at the beginning of a BASIC program. REM statements are, of course, text comments, so this meets ...

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22 answers
106 votes
38k views
Was there ever any reason to wait 30 seconds to restart a c.1995 PC?
12 votes

You are still recommended to wait about 30 seconds when turning a modern computer off and on again. The risk of any damage was very small but not zero. The risk nowadays is probably even smaller due ...

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3 answers
11 votes
743 views
BBC model B, 20 pinouts port on keyboard below speaker used for what?
12 votes

Most hobbyists put a ZIF socket onto those pins. This then was connected through to the sideways ROM sockets on the motherboard. The socket enabled you to insert language ROMs as required, thus ...

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2 answers
10 votes
540 views
S-100 bus and device drivers
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12 votes

Like most busses of its time, you had to write your own software to communicate between the cards. The term device driver wasn't widespread at the time, but that is what you were writing. The S-100 ...

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2 answers
20 votes
2k views
Actual code written by Ada Lovelace?
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12 votes

Ada Lovelace didn't write any code as such. This is largely because the Analytical Engine, being created by Charles Babbage was never finished and so no code could be run. Babbage designed the ...

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3 answers
11 votes
939 views
Was the PDP-11 coroutine instruction actually used?
11 votes

Well, I used it. Back in the late 1980s, I led a small team who produced a signalling message distributor for British Rail (as it was then). This was on the PDP-11 in a mixture of C and Assembler. ...

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1 answers
10 votes
732 views
How can I hook up my Acorn RISC PC 600 to a LCD monitor?
11 votes

The RiscPC was Acorn's first to use a separate RAM bank for the video. It was intended that the video drivers would auto-synch to the monitor. However, there was often a failure to synch, leaving ...

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2 answers
5 votes
323 views
Could we change the baud rate for the two serial ports on a terminal and on a computer?
10 votes

The short answer is yes. You can change the baud rate of a VT100 talking to a PDP-11. On the VT100, this is simply done using the Set Up facility. This is entered using the Set Up key on the top ...

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1 answers
10 votes
371 views
What should I do to clean up a Power Mac G3 that's been outside for two years?
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10 votes

From your description, it sounds as though there is no fundamental reason why you shouldn't get this machine working again. The main risk is something somewhere causing a short circuit. So, don't ...

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4 answers
26 votes
42k views
How can I connect a DIN plug keyboard to USB?
10 votes

There are two aspects to this. The cable for the physical connection and the driver for the communications protocol. I suspect with adaptor upon adaptor you are either losing voltage and therefore ...

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2 answers
12 votes
887 views
How do I replace a ZX Spectrum 48k keyboard membrane?
Accepted answer
10 votes

For the keyboard itself: Undo the screws from the bottom of the case. Lift the top of the case gently off. Disconnect the ribbon cables from the keyboard (CAREFUL fragile) Slide out the keyboard. ...

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1 answers
8 votes
361 views
How many bits are stored in a memory location in a PDP-11?
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9 votes

The PDP-11 could address 64kb of memory. It handled data as words, each word being addressed at an even memory location. So it depends on what your "data read instruction" is. If you issue a MOV ...

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1 answers
14 votes
240 views
What happens on a VT102 when you use delete character on a reverse video line?
Accepted answer
9 votes

I can only provide my memories of a dozen or so years of programming for these DEC terminals. The 'new' character at the right hand end of the screen is inverse video. If I recall correctly, on the ...

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1 answers
3 votes
197 views
Porting of software from the m68k family architecture to the DEC VAX
8 votes

I can give you an anecotal answer. I did this a few times. I suspect that porting in this direction would have been unusual. We only did it where the customer insisted on the use of Vax hardware. ...

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