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Questions tagged [sinclair]

For questions regarding computers made by the Sinclair group of companies: Sinclair Research, Sinclair Radionics and Science of Cambridge.

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What does Spectrum BASIC have that ZX81 lacks?

The Sinclair ZX81 has 8K BASIC interpreter ROM; the Spectrum has 16K. What extra features does the Spectrum put in the extra 8K? The most obvious thing is commands for color graphics, which are absent ...
rwallace's user avatar
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11 votes
1 answer
1k views

Using Sinclair ZX Microdrive is it possible to random access a text-file?

I wish to build a small database using Sinclair ZX Microdrive: one can think to create a text file using some simple BASIC. For simplicity let's say the record is 512 bytes in length, i.e. the same as ...
Matteo Vitturi's user avatar
8 votes
3 answers
391 views

What is the correct power supply for this SD card/cassette reader for Sinclair computers?

I bought this some time ago, but I did not keep the power supply with it. It does not have any product name on it, and I can't locate the correct information. What is the correct power supply and what ...
Zhro's user avatar
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14 votes
4 answers
3k views

Why does Sinclair BASIC have all of the characters twice in the token table?

I'm looking over the table of tokens for Sinclair BASIC and I'm struck by two things. One is that it's not ASCII. Some parts are in the same order, but others are not, so it would seem conversion is ...
Maury Markowitz's user avatar
5 votes
1 answer
271 views

How many units of the ZX81 RAM pack were sold?

The Sinclair ZX81 was an extremely popular low-cost home computer, on strength of price, being a computer for less than 100 pounds. It sold over 1.5 million units, according to https://web.archive.org/...
rwallace's user avatar
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34 votes
8 answers
4k views

What made some 8-bit BASIC interpreters especially slow?

Most 8-bit systems had a BASIC interpreter that ran at a rate roughly commensurate with the CPU type, speed, memory bandwidth and interrupt status. Some systems, however, had interpreters that ran at ...
scruss's user avatar
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14 votes
3 answers
2k views

What was Sinclair's intention with the Microdrive?

The ZX Spectrum was announced with support for both standard cassette tapes and Sinclair's new Microdrive format -- although the latter wasn't released for another 17 months. Given that the necessary ...
Den's user avatar
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16 votes
3 answers
2k views

Is there any significant difference in Sinclair BASIC of ZX80, ZX81 and ZX Spectrum?

I'm trying to write some programs from an old magazine that were specified to run on an ZX80/ZX81 but I'm using a Sinclair BASIC interpreter for the Spectrum. Is there any significant changes in BASIC ...
d'Arby's user avatar
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3 votes
2 answers
458 views

Spectrum 128K +2 Power Supply Buzzing and over voltage

I've seen a similar question to asked here but but I'm not sure it fully addresses the issue I'm having. I'm using a PSU the same as this one from the 128K +2 According to this site, this PSU ...
iamkl00t's user avatar
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9 votes
1 answer
405 views

Can the TMS1802/0102, or specifically the Sinclair Executive calculator, handle an attempt to divide by zero?

There's a sort of urban legend among people I've spoken to about Sinclair that the Executive calculator can't divide by 0. Specifically, if you do this then it goes into a busy loop, cannot be used, ...
Graham Lee's user avatar
9 votes
1 answer
382 views

Can you switch the ZX81 ROM to RAM w/o write protecting it and still use ZX81 BASIC?

I built an external 8K RAM circuit that replaced the 8K ROM of Sinclair ZX81 and I also pulled out address lines from the ULA (dogsbody) so that character generation worked. I wrote a small machine ...
mobluse's user avatar
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19 votes
1 answer
3k views

Why does the ZX81 not have user definable characters without extra hardware i.e. why could the character ROM not be in RAM?

I know you can use different parts of the 8 KB ROM in Sinclair ZX81 as character ROM by changing the I register, but it seems one cannot change the I register to point to RAM [and have character mode]....
mobluse's user avatar
  • 505
25 votes
4 answers
6k views

When did half-bad RAM chips stop being available?

The ZX Spectrum sold with either 16 or 48K RAM, necessitating an optional 32K memory bank which was achieved in a characteristically (for Sinclair) cleverly frugal way: with half-bad 64kbit DRAM chips,...
rwallace's user avatar
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2 votes
0 answers
147 views

How many people were employed in the UK making Sinclair computers?

According to Wikipedia Sinclair Research had only 140 employees at its peak in the 1980s. I was surprised the number was so small for a company that sold something like five million computers, then I ...
rwallace's user avatar
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7 votes
1 answer
899 views

What non-Spectrum computers did Sinclair sell 4 million of?

Reading Alan Sugar : The Amstrad Story, I just came across one of those little oddities that initially manifest as 'huh, wait a minute' and sometimes just mean someone has made a typo, and sometimes ...
rwallace's user avatar
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8 votes
4 answers
777 views

Who produced all-in-one / wedge style IBM compatibles?

The RetroManCave YouTube channel recently made me aware of the Sinclair PC-200 / Amstrad PC-20 and I already knew about the Tandy 1000EX / 1000HX but were there any other IBM-compatibles (or mostly ...
Sam's user avatar
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9 votes
2 answers
703 views

Sinclair's microdrive -- was it based on compact cassette technologies?

Recently I've also looked inside microdrive drives of Sinclair QL and inside microdrive cartridges for it. The tape looked like a compact cassette tape cut longitudinally to a half width (which seems ...
lvd's user avatar
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14 votes
4 answers
2k views

Were there really any cost savings in Sinclair QL because of it being 8-bit design with 8-bit bus 68k CPU?

I've recently looked into the Sinclair QL schematics and found that it actually has two 8bit ROMs, 16 4164 DRAM chips and yet it is purely 8bit machine, even the 68008 there has 8bit bus. With very ...
lvd's user avatar
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6 votes
1 answer
413 views

Are all 64k x 4-bit ICs interchangeable for Amstrad-era ZX Spectrum 128k +2/+3?

There were 4 64k x 4-bit Integrated Circuit chips in the Amstrad-era Sinclair ZX Spectrum +2 and +3 models. These are known as the +2A, +2B (both +2 "black"), +3 and +3B (also both black cases). I ...
popeymon's user avatar
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11 votes
3 answers
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Is it possible to PRINT AT 23,0 in ZX Spectrum BASIC?

The ZX Spectrum BASIC doesn't (ordinarily) let you print on lines 23 and 24 to allow for user input. Is there a way around this? I found a fairly recent post that suggested I could POKE 16418,0 but ...
Remy Sharp's user avatar
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12 votes
2 answers
2k views

Why did the Sinclair QL keyboard lack a Delete key?

It seems like an odd key to omit, given how frequently used it is and given that both the Spectrum + and 128 have one, which acts like backspace does on a modern PC. They could have swapped it for two ...
user3570736's user avatar
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13 votes
1 answer
1k views

Why did the ZX81 16K RAM pack use two PCBs?

The ZX80/81 16K RAM pack used two PCBs joined with a connector in the middle. I'd initially assumed this was due to reuse of the original 3K RAM pack case (which has a single PCB and uses static ram)...
PeterI's user avatar
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2 votes
1 answer
194 views

Did the ZX80 RAM pack pass the expansion bus through?

The ZX80 only came with 1K of RAM, which had to be shared between program and screen memory, so many customers bought the Sinclair 16K RAM pack, which plugged into the expansion bus (the edge ...
rwallace's user avatar
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29 votes
3 answers
6k views

Why did the ZX80 CPU run at only 3.25 MHz?

The Sinclair ZX80 used a Z80A running at 3.25 MHz. But this chip was rated for 4 MHz. Why was it run below rated speed? Apparently the master clock in the machine ran at 6.5 MHz, so the CPU clock ran ...
rwallace's user avatar
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10 votes
1 answer
1k views

How did the ZX80 RAM pack use DRAM?

The Sinclair ZX80 was the most popular personal computer in Britain at the beginning of the 1980s, due to its low price which was enabled by extreme minimalism; it consisted of not much more than a ...
rwallace's user avatar
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7 votes
1 answer
692 views

Why is ZX80 much faster than Spectrum on Rugg/Feldman benchmarks?

If you look at the results of the Rugg/Feldman benchmarks, shown in this Wiki entry, you'll see that Sinclair ZX80 is much faster than Sinclair Spectrum on all tests despite the fact that both ...
neutrino's user avatar
  • 173
4 votes
1 answer
333 views

How to determine PCB revision of a Sinclair ZX-81

I have a ZX-81 in my collection, but do not know what revision it is. The board text just says "Sinclair ZX81". As far as I know, there were 3 revisions of the ZX-81. What are the landmarks I can ...
user avatar
6 votes
1 answer
582 views

Timex Sinclair 1500 and screen "jail bars"

I have tried to eliminate "jail bars" on the screen after UHF mod to video out (based on that: http://zx81stuff.org.uk/zx81/ts1500_video.html) by adding 460uf 16V capacitor between +5V and GND but it ...
JackTheKnife's user avatar
18 votes
8 answers
1k views

Cambridge Z88 Production Run

While this is not a technical question per se, I finally found something I have no idea and couldn't find any answer online: How many Cambridge Z88s were made and/or sold? As it's related, a sub-...
Raffzahn's user avatar
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28 votes
2 answers
4k views

Why does this BASIC program declare variables for the numbers 0 to 4?

On pages 150 to 154 of William Tang's (1982) Spectrum Machine Language for the Absolute Beginner, there are these lines of code. (Note GOTO 9000 is the first non-REM statement in the program). 9000 ...
harlandski's user avatar
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23 votes
6 answers
4k views

ZX Spectrum tokenisation

The BASIC used in the early ZX Spectrum (and also its ZX predecessors) had this weird thing where every single BASIC token was printed onto the keyboard, and for example PRINT or LOAD were entered by ...
Omar and Lorraine's user avatar
29 votes
2 answers
5k views

Why did Sinclair choose the Z80 for its range of home computers?

The Sinclair computers are known for their low cost compared with other computers that were popular in the early 1980s. This is why they had membrane keyboards, or that rubber stuff in the case of the ...
Omar and Lorraine's user avatar