Spectrum +3 differences.

[McKlain]

Just put some midi on it and I'll bought it XD

[redbox]

I thought so, so it's SID we'll be concentrating on

I'd be happy with having a SID attached to the CPC[nb]Having said that, I do still love the AY.[/nb].


And when the C64 fanboys start smarting, I would also point out that it's the only part of the breadbin worth worrying about.


CPC with SID attached = ultimate C64 killa. 

[Badstarr]

Ok I think this could be a really cool project! Sound synthesis is my thing and the SID looks quite interesting! Apparently it has an audio in pin, so it can be used as an effects processor. So we could go one better than the Commodore gang and have the AY routed through it to get all sorts of circuit bendy sounds! It has also plenty of waveforms and 3 oscillators so it could be possible to have some sort of synth frontend that ties the two chips together, a bit like Reason if anyone has used it, although the number of different configurations would be limited.


I will have a more in depth look but I think it may even be possible to create a basic FM synthesis by combining both the SID and the AY via the audio in pin!

[McKlain]

You can see a lot of videos in youtube with people modifying the C64 to add external controls for the sid filters, there are also midi cartridges and sequencers for the c64 and I think that the audio processing have been used in some of the later "reimplementations" of the chip, but I can't remember well.

http://en.wikipedia.org/wiki/MOS_Technology_SID#Hardware_reimplementations

As the wiki says: 'Even though Yannes was partly displeased with the result, his colleague Charles Winterble said: "This thing is already 10 times better than anything out there and 20 times better than it needs to be."'

An outstanding work indeed, he did it in just 6 months from scratch.


By the way, the fact that the sid is not stereo makes sense if you look at the features and synthesis capabilities of the chip, as it doesn't have "channels" but "oscilators" that can even modulate each other or be hard-synced.

[Badstarr]

If the oscillators can modulate each others frequency at above say 15-20 Hz then we have hardwired FM synthesis built into the SID. What would be fantastic is if it can do the same to the audio in pin signal, the possibilities increase a hell of a lot! With the AY becoming a 4th Oscillator ! Imagine being able to make sampled speech sing for example. If the SID can delay and feedback signals, basic physical modelling synthesis is possible too. 

[McKlain]

I remember that many of the classic songs from c64 videogames used hard syncing, ring modulation and filter tricks to make "strange" synth sounds.

By the way TFM/FS, you can hear some deep bassdrums on this one 

Well, hearing that bassdrum you could say that Rob Hubbard invented the Gabber drum sound on the c64 in 1987 

[Jase]

Yes, 2 AYs would be possible too, but do you know anyone with a spare AY?

Um. Yes. Me.
I was thinking of piggy-backing it onto another one, but having 1 AY on a clean power, and hopefully getting clean outputs.
But it was a silly idea that never got further than extracting the AY out of a 464 board.

[Executioner]

If anyone can get their hands on a box full of AYs, I'll build them whatever they want out of them. Hell I'll even do 8x AY if the parts are available.......

Deafening silence......

Err, is 128 enough? http://www.ebay.com.au/itm/1-AY-3-8910-8910A-YM2149F-AY38910A-Sound-Generator-IC-/360363014602?pt=LH_DefaultDomain_0&hash=item53e74f39ca

[TFM]

To compare...

[Gryzor]

Err, is 128 enough? http://www.ebay.com.au/itm/1-AY-3-8910-8910A-YM2149F-AY38910A-Sound-Generator-IC-/360363014602?pt=LH_DefaultDomain_0&hash=item53e74f39ca

Bryce, hope your hat is tasty enough :p

[McKlain]

To compare...

And still a great song. Last night I saw Rob Hubbard giving a speech on Assembly 2007 I think, and as a programmer he wasn't too fond of the spectrum or the amstrad (he said that the machines were "a dog to program to" XD) In fact he didn't like the Z80 or the AY too much.

[Bryce]

For $9.70 (€7.27) I'll leave my hat where it is. (I don't recall claiming I'd eat it anyway though). Also, these are AY-3-8910, ie: the 40pin version with Port B available. I'd prefer to work with the AY-3-8912, due to PCB real-estate, and the fact that I really don't need four extra ports.

Bryce.

Edit: I just checked my own supplier. He can supply the AY-3-8910 for €5.50 including postage.

[Gryzor]

Ah, you're going into fine-print mode now, ain't ya?

[Bryce]

Mode 2

Bryce.

[dragon]

I have received the spectrum ula book,Basically is centred in the ula(sinclair) era,and only a pair of annotations is dedicated to amstrad era.


Basically the spectrum ula as a fault design in memory contaiment.(The circuits control the z80 and the ula not access to the ram at the same time).In revisións of spectrum,the spectrum received external patchs to solve it.But in all ula revisions,internally is not complete solved.(in part to compatibility games questions,in part to time necesary to implement the solution)

When amstrad take control of spectrum desing.As they had to rewrite the circuit to implement the new ASIC.They pulled out of the way down the street.And rewrite the cirtuit memory contaiment.And ported the memory map of cpc to spectrum(memory divide in 16k bloks).

Also the book is very interesting,it's help understand how are constructed the microcomputer in generally.So indirectly it can help understand the gate array.Because it's explain how the pixel clock is calculated in base a resolutión and a general tv parameters.And how palette colours is generate.And explain the general methods to memory contaiment in z80.

[Bryce]

Sounds like a great read. Any chance that you might throw it onto a nearby scanner and let some more people read it?

Bryce.

[MaV]

While I don't have any qualms about copying old 8-bit software and scanning old computer books, the ZX Spectrum ULA book is still on sale (Published August 2010). Scanning is not a good idea.

[Bryce]

It is?? I thought he was referring to some old 80's book! Do you have a link to where I can get it?



Bryce.

Edit: Found it already myself

[MaV]

Edit: Found it already myself

Argh! Too late. What's even worse, when I wrote the first post, I already had the intention of inserting the link. *grml*

[Bryce]

And..... Ordered

Bryce.

[Gryzor]

Ok, I'll wait twenty years, then I'll ask you guys to scan it

(reminder set...)

[McKlain]

Interesting note: the book is cheaper in amazon.es (the spanish site) than any other amazon european site.

http://www.amazon.es/ZX-Spectrum-ULA-Design-Microcomputer/dp/0956507107

[dragon]

So I the only of amstrad that buy the book?(bryce apart).


Its very interesting how is designed a color palette with a primitive dac.(a bunch of resistances lol).I sure that the gate array uses the same system but with 3 bits,an more more resitances XD.

Basically the diference of gate array and ula is than amstrad enginers uses external chips to make stuff that ula make internally(the keyboard with ay for example).This saving space in amstrad gate array.And amstrad can inftroduce more circuity dedicated to video.Also amstrad use stardad tecniques to pixel generatión.when spectrum use tecniques totally unstandard.I think amstrad limited the 16 colours in mode 0 to maintain a 16k standard memory video and save  logic gates.

So,if you like z80 harwdare stuff (even without a spectrum) i recommend the book.

[Bryce]

The Amstrad techniques are interesting, because you can see that almost every decision was made to reduce the cost. Right down to the stupid idea of putting both joysticks on one socket. The Spectrum is a very strange design from an electronics point of view. There were already very good standard solutions for many of the issues they had, but they came up with new and sometimes very inventive solutions. Although I suspect (based on the solutions they came up with), that some of the hardware designers came from a radio/analogue background and had no significant microcomputer experience. One of the very creative solutions can be seen in the 16K/48K ZX Spectrum, where they chose a single 9V power supply and then built a cheap but rather complicated circuit to produce 5V, 12V, isolated 12V and -12V. All made from a few standard components.

I doubt there's much for me to learn from a technical point of view in the book, but it's the nostalgic stories of the "whys and hows" that I'm really looking forward to.

Bryce. 

[dragon]

The books is repleat of why and how  .

The principal problem in  the design of the spectrum is the capacity of the ula.

The ula is a matrix of 11x11x4(726 gates Nor or and).I'ts very litte space.And many of the decisions is influenced by the space.

I not know the why of voltaje(I no read the entire book XD).

The curiosity is if you counter the number of ttl chips in the pic of cloned ula and the number of ttl in amstrad gate array simulator.is almost the same number of integrated ttl chips.