Internal AY-8912, has anyone tried it?

[1024MAK]

Definitely ask any questions, there are both hardware and software tinkerers here

Mark

[kokkiklhs]

Please don't let anything I say put you off. I just wanted to give you a few pointers that's all.

The joy of doing a project to completion doesn't matter if any body else wants it because it is for your satisfaction of a job well done,the journey and problem solving along the way, and remember there are a lot of very knowledgeable gurus on this forum (not me ) who I know would be happy to share their expertise with you.


If you look at the posts above by anightin then you will see he/she is trying to get something to work for the ACE so perhaps you can swap ideas etc.

Please persevere with it as all zeddy projects are worth it and I wish you all the best for it.

Moggy.

Gee, thanks, I know exactly what you mean! It's a great pleasure to see any project finished, even if it's totally useless or pointless... I'll try it, but it needs a lot of time (for studying/asking about some details before) which I don't have right now... The only caveat is the lack of software, but if something like that is finally made one day, it will be perhaps a good chance for software developers to produce more stuff for stock AY-equipped Zeddies, without ZXPand etc...

Definitely ask any questions, there are both hardware and software tinkerers here

Mark

Thanks, once I start, I will surely be needing A LOT of advice!!

Cheers to both of you and Merry Christmas to the whole Zeddy community!!!

[shock__]

How much height does the original ZX81 case have left for the CPU socket? On an Issue One it should be possible to add a pretty daughterboard if you have ~15mm left (or less if you solder in the CPU and solder the daughterboard directly on top ... or none at all if you design a daughterboard that replaces the through hole CPU with a SMD one). Otherwise it should be possible in any case using "deadbug"-style ICs + loose wires.

I could definitely see this work, but recently got rid of my last ZX81 and to be perfectly honest here have no interest in designing hardware for the ZX81.

[1024MAK]

Not much height. About 18mm from the surface of the PCB to the plastic case. Slightly less at the front due to the case sloping downwards.

Mark

[Moggy]

The UK H4th ROM came on a daughter board that replaced the Sinclair ROM and the original US Pluri forth version on which H4th was based had both the original and Forth ROM on the same board along with the wiring that connected to the channel switch,now used for ROM switching, so some scope for fitting a board especially with modern small components I would have thought.

The area under the keyboard is a possibility too as I seem to recall that being a favourite space for fitting Karl's video boards.

The attached picture when zoomed in should give some idea of how a daughter board would fit .

Link to the original article.

https://archive.org/stream/SyncVolume4N ... 7/mode/2up

[jdfan1000]

Independence Research made a 64K internal expansion for the ZX81/TS1000. Based on the images, it looks like they mounted it through the Z80 socket. There is a very low res image here: https://www.timexsinclair.com/product/64kt-64kz/

[fordp2002]

I am working on getting the ZX21 sound working. I am using the YMZ-284 chip board option and I have typed some of the programs in from the ZONX81 Manual (Ian Priddey).

I will as at the very least add the .p files to my github.

[Mustermann]

Ok, four and a half years later....

I had some thoughts about that.
The biggest issue about internal AY are space and cables (at least from my point of view).

The schematic of ZonZ81 is known. AY+ 3 logic chips + audio amplifier.

I already got some experience with hiding SMD parts under the CPU or ULA.
As I also build an internal 96k ram expansion. so the only place left in my zx81 is under the ROM.

At the socket of the ROM D0-D7, A0-A4, and A7 are available.
/IORQ, /WR and clock are missing.

So number of cables can be reduced to 3 (plus audio output).

Now about space:
AY-3-8913 is the smallest one but still same size as the ROM itself, so will not fit below it.

Right this week I noticed that there is an AY-3-8913 emulator that is using an ATmega48 in an 32TQFP package.
https://github.com/Yevgeniy-Olexandrenko/avr-ay-board

I assume that ATmega, 3x74xx and a crystal will fit under the ROM if the PCB will stick out a little bit.

Audio amplifier and speaker can be mounted elsewhere under the keyboard.

Might this be feasible?
Is an emulated AY-3-8913 ok?