BEEP VAL

The place for codemasters or beginners to talk about programming any language for the Spectrum.
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ZXDunny
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Re: BEEP VAL

Post by ZXDunny » Thu Jul 18, 2019 6:34 pm

"ok, we need to make an upgraded ZX81. What can we get for the same cost as the '81 cost when it was launched?"

"We can add colour. We could use full or empty RGB channels to get 8 colours, and probably a halfbright by setting an extra bit."

"No interesting colours like the commodores then?"

"Not if you don't want to spend any money."

"Ok, that'll do then. We'll call it a 'Spectrum' and they'll love it. What else?"

"We could get a full 64k of RAM?"

"With a 16k ROM?"

"No, that would cost more, we'd need some sort of paging"

"Bugger that, let's launch it as 48k. It's still more than 1kb. And we could launch two models, and charge more. What else?"

"Sound?"

"Can we do sound? What's the minimum we could go for?"

"A piezo buzzer that we can toggle on and off. We could add it to the graphics chip. But there are better chips out there for sound."

"f*** 'em. A buzzer will be plenty good enough, it's not like anyone will make music with it, this is a glorified calculator like the last one.
Hmm. That graphics chip. What else can we cram in there?"

"Tape loading? We could use it to listen to the tape. Oh, and we could use it to read the keyboard too."

"Do it. Just keep the cost at a minimum. We're not going to make any money if this thing costs £300."
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Re: BEEP VAL

Post by AndyC » Thu Jul 18, 2019 7:08 pm

1bvl109 wrote:
Thu Jul 18, 2019 5:55 pm
AndyC wrote:
Thu Jul 18, 2019 5:29 pm
... they didn't even get all the Interface 1 code into the ROM as they had originally planned.
Interesting. I never header about this. What ROM are we refering here to?
The BASIC ROM, it was originally supposed to contain all the microdrive code, but it wasn't ready it time and so got dropped for a slightly hacky solution in the Interface 1
1bvl109 wrote:
Thu Jul 18, 2019 5:55 pm
AndyC wrote:
Thu Jul 18, 2019 5:29 pm
They had been producing a new model on a yearly basis, they could always do things better in the "ZX83" - the Speccy was never envisioned as staying around even half as long as it did.
Fair enough. However I'm not satisfied with the 128k either.
The.128 design wasn't really a Sinclair thing, it was a Spanish spin off (Investronica?) that stemmed from rules at the time which applied additional taxes on computers with less than 64K (they were seen as entertainment items). They threw in a few extras to make it a bit more appealing, but it was a quick and dirty upgrade. Not quite as cheap a solution as Amstrad, who made a CPC472 by just soldering and unconnected 8K of RAM inside a standard 464 to solve the same problem!
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Seven.FFF
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Re: BEEP VAL

Post by Seven.FFF » Thu Jul 18, 2019 7:24 pm

ZXDunny wrote:
Thu Jul 18, 2019 6:34 pm
"Tape loading? We could use it to listen to the tape. Oh, and we could use it to read the keyboard too."
Expanding on my earlier observation that the ULA beeper circuit is the same circuit that outputs the tape MIC signal... it's almost certainly similar to the ZX81 tape circuit too. It's not like Altwasser invented it from scratch for the Spectrum.

I'm veering into conjecture here, but he already had the ZX81 circuit, was aware of it's reliability issues, fixed those in a minimum viable way, then bingo, free buzzer feature too! Job done, with the absolute minimum of work.
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Re: BEEP VAL

Post by Seven.FFF » Thu Jul 18, 2019 7:27 pm

1bvl109 wrote:
Thu Jul 18, 2019 5:55 pm
My theory is that the ZXs should appeal to hackers. And to gamers, i.e hackers who do games. So hackers it is. They like things which are transparent, pushed to the limit and extendable.
That may be what we'd all like to be true, but the reality is different. Many of the decisions they made make it much harder for hackers, and edge connector hardware designers :)
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1bvl109
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Re: BEEP VAL

Post by 1bvl109 » Thu Jul 18, 2019 8:01 pm

ZXDunny wrote:
Thu Jul 18, 2019 5:37 pm
But it would have pushed up costs. Adding any extra hardware would have pushed up manufacturing costs.
As would have better software.

So, don't add it, just make the machine flexible enough to be able to add it later. Then sell it. Maybe you need a few lines more on the edge connector. And here's your ULA+ for a nice steep price. How about a 128/256/1024 RAM pack?

Alternatively just bring out an early successor which can do this. Going incompatible where you need to. We have lots of revisions of the board already.
ZXDunny wrote:
Thu Jul 18, 2019 5:37 pm
So it was never going to happen. This was a computer done as cheap as possible but still, as has been pointed out, a recognisably better ZX81.
You have to pay for recognizable better however.
ZXDunny wrote:
Thu Jul 18, 2019 5:37 pm
And besides, Sinclair didn't add anything. We can't go back and change it so there's no real point to this.
I don't mean, repeat don't mean to bugger the old man. He had to organize a company. I never did such a thing. I have some basic understand of electronics 40 years ago. This is it.

Of course hope goes on forever and maybe somebody somewhere is sitting down with a Z80e thinking what would be needed to make a cheap as dirt successor.
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1bvl109
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Re: BEEP VAL

Post by 1bvl109 » Thu Jul 18, 2019 8:23 pm

Seven.FFF wrote:
Thu Jul 18, 2019 7:27 pm
That may be what we'd all like to be true, but the reality is different.
You caught me with my pants down, Mr. Feuerbach.
Seven.FFF wrote:
Thu Jul 18, 2019 7:27 pm
Many of the decisions they made make it much harder for hackers, and edge connector hardware designers :)
Doubtlessly. But were they "After careful consideration we'd rather not"-, "We don't give a sh*t"- or "We have no time to even considerate this"-decisions? Or what else was the consideration behind the decision?
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1bvl109
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Re: BEEP VAL

Post by 1bvl109 » Thu Jul 18, 2019 8:36 pm

ZXDunny wrote:
Thu Jul 18, 2019 6:34 pm
"We could get a full 64k of RAM?"

"With a 16k ROM?"

"No, that would cost more, we'd need some sort of paging"

"Bugger that, let's launch it as 48k. It's still more than 1kb."
I especially like that.

But we would also be able to bring out revisions of the ROM on tape. And sell memory extensions as we did with the 81! And bring out hardware extensions with new custom ROM routines! Of course there will be competition, e.g. like the race for the lowest price for the 16k RAM for the ZX81, but we will always have an edge, knowing the design already and therefore being first to the market.
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ZXDunny
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Re: BEEP VAL

Post by ZXDunny » Thu Jul 18, 2019 10:03 pm

Having 64k RAM with the ROM on a media was a thing with the Amiga 1000 - Kickstart up to 1.3 came on floppy disk to be written to the "ROM" (which I use in quotes there as it was only semi-permanent; it survived a soft reboot but not a power-down). The thing was it only took a few seconds to read and you were good to go. I upgraded my kickstart a couple of times that way as I went from 1.0 to 1.3.

But for a Speccy? 16kb of tape took a while to load. Having to do that every time you booted up would be a real PITA. And as the Speccy had no soft-reset system (which would have cost more to put in - witness the 48k+'s reset switch that literally cut the power, grounding the CPU - minimal cost) the ROM would have to be re-loaded after every game you played.

It's unlikely that as attractive as a full 64kb was making it work just was either too expensive or too unfriendly to the user.
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Re: BEEP VAL

Post by 1024MAK » Thu Jul 18, 2019 10:05 pm

Hmm, I think something got lost, now what was it?

Ahh yes, Sir Clive Sinclair set the specifications. As the owner of the company he was responsible for deciding what features were in and which were dropped.

And you do know that Clive aimed the ZX Spectrum at the educational market and the hobbyist market. It was never intended to be a games machine.

From the limited information available, I get the impression that the ZX Spectrum ULA was the most complex ULA that Ferranti has made at the time. So it may already have been pushing the limits...

Oh, and by the way, Sinclair expected the 16K byte ZX Spectrum to be the most popular, not the 48K byte model. The 16K byte ZX Spectrum was upgradable internally or externally, hence 32K byte RAM packs do exist.

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Re: BEEP VAL

Post by 1024MAK » Thu Jul 18, 2019 10:10 pm

ZXDunny wrote:
Thu Jul 18, 2019 10:03 pm
And as the Speccy had no soft-reset system (which would have cost more to put in - witness the 48k+'s reset switch that literally cut the power, grounding the CPU - minimal cost) the ROM would have to be re-loaded after every game you played.
Err, the ZX Spectrum+ reset button is connected to the existing resistor/capacitor ‘power on’ reset circuit that in turn connects to the Z80 /RESET pin. Nothing wrong with that. The only cheap bit being no proper PCB connector.

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