ZX-2012

[BlackCanyonFX]

Hello all,
Apparently I am being mocked, I.E.-

siggi-> "And enable ram for UDG and/or HRG"
"And a M1-NOT logic to enable execution of MC above 32K?
And a switch to disable the M1-NOT-logic to run also big basic progams (> 16K)"

Well, duh. Of course anything is possible. BTW - The 'MI-Not' mod is in my layout.

I am seriously thinking of goimg to copper on this. The thoughts,
comments that I expected were a bit more on the lines of, " How about
ususing the clock batt for the RAM as well?".

ATM the boards in 4-layers will cost me about $54ea through a fab house
that I have a current working relationship with. No Biggie.

I'll do it with or without constructive input, reguardless.

I'm not being snippy (I hope) but WTF?

Here is a link to a .3ds of my current route. I did this to see if I had the room
to go further.

http://www.timidbull.com/downloads/ZX-2012.3DS


On A personal note....
Siggi- Ya kinda just hurt my feelings...you and Wilf have always been the internet
"heros" I've never been able to talk to.

once again...I mean no hard feelings....

Gregory T. Blocker Black Canyon FX, AZ

[RWAP]

I don't think siggi was mocking you - certainly I think this is an interesting project, but I think the point siggi was trying to make, was that maybe before you go too much further, you need to consider some of the other improvements which have been made to the ZX81 over the years, rather than just make a new ZX81 motherboard.

Looking at your mock up design, you seem to still use the two cassette deck connectors - I wonder whether it would just be easier to go for an SD card adaptor (offering similar facilities to ZXpand, rather than that remaining as an add-on option).

I can see you intend using a USB keyboard - though I am not sure what the connectors are for down the bottom right hand corner of your picture - are they supposed to be molex keyboard connectors (they seem to be pin headers?)

As for the comment about "enable ram for UDG and/or HRG" refers to the fact that a lot of recent software (see http://www.rwapsoftware.co.uk/zx81/zx81_software.html ) is reliant on RAM which supports UDG and/or HRG schemes - the standard ZX81 plus 16K RAM pack do not support this without modification to the RAM pack (or use of the ZXpand).

We all want to support you in your efforts, I am sure, it is just that it would be nice to get the best features which were developed for the ZX81 over the years into one new compact machine (if it is possible within size and budgetary constraints).

[siggi]

I don't think siggi was mocking you - certainly I think this is an interesting project, but I think the point siggi was trying to make, was that maybe before you go too much further, you need to consider some of the other improvements which have been made to the ZX81 over the years, rather than just make a new ZX81 motherboard.

(..)

We all want to support you in your efforts, I am sure, it is just that it would be nice to get the best features which were developed for the ZX81 over the years into one new compact machine (if it is possible within size and budgetary constraints).

That is also my opinion.

And some enhancements (M1NOT-circuit with a jumper to disable it to run big BASIC programs, ram enabled for HRG, Wilf's new WAIT logic) do not require much effort, but having them on the main board would be a big advantage ...

Most of that features are built into my Laptop-Zeddy. But it required a lot of soldering ...

Siggi

[BlackCanyonFX]

It is I who must appologize...

"I don't think siggi was mocking you - certainly I think this is an interesting project, but I think the point siggi was trying to make, was that maybe before you go too much further, you need to consider some of the other improvements which have been made to the ZX81 over the years, rather than just make a new ZX81 motherboard."

I intended from the beginning to simply replace the ULA with the "ZX-97", "Mini-ZX", etc. circuits. My old PIO stuff fell in somehow and a few odds and ends.

I was very amiss in the way I started this thread. I really had two seperate questions.

1. Is the current sch correct as far as what I have 'stolen' from previous ULA replacement designs?
2. (and this is where the mis-understanding lies...) what should I change (i.e.Siggi's thoughts) before I order a test run?

So... I'm ready to go ahead and have a few made if they meet my weird req of fitting a stock ZX case (with a few cuts for conn slots).

Which leads to...
"I can see you intend using a USB keyboard - though I am not sure what the connectors are for down the bottom right hand corner of your picture - are they supposed to be molex keyboard connectors (they seem to be pin headers?)" Yes, they are, to remain ZX-compatible.

As to your last observations, Rich...

"We all want to support you in your efforts, I am sure, it is just that it would be nice to get the best features which were developed for the ZX81 over the years into one new compact machine (if it is possible within size and budgetary constraints)."

I deeply appreciate the help and community of this forum. I failed to make myself known to you, and the rest of this community. I failed to make my intentions clear with this board design as well.
I am not trying to make "big bucks" on this (though a few wouldn't hurt ). My fab house will cut me as may boards as fit in 155 sq.in. for about $300 for 4 layers or $110 for 2 layers. With two side silk, I figure $54ea 4-layer or $20ea 2-layer. GoldPhoenixPCB.com
I have worked with these folks before, and I have no problem with ordering the boards.

PS- "(if it is possible within size and budgetary constraints)"
It MUST fit a ZX case and ...and...I don't know...let's just see where it goes? 4-Layers anyone?

[BlackCanyonFX]

On a personal note to Siggi...sorry 'bout that.........

[siggi]

2. (and this is where the mis-understanding lies...) what should I change (i.e.Siggi's thoughts) before I order a test run?

Hi Gregory,
I would disconnect /OE of U28 from /CS of U28 to avoid possible timing problems. I described them here:

viewtopic.php?t=407#p3219

So
/CS(U28) = /RAMCS
/OE(U28) = /RFSH AND /RD

HTH Siggi

[BlackCanyonFX]

Hello All,
I'm sorry about my recent absence. I lost internet yet again (modem and computer crash at once).
TG for neighbors (with strong wi-fi and kind hearts).

Thank-you Siggi for the input. I totally missed that one. I also need to add the batt back-up to the
RAM. I have been working on the USB keyboard conversion from the AT version on the web, but it has
been a bit difficult without the net (normal speak= I haven't got it yet...).

Somewhere back at the beginning of the thread I remember saying why I named this project 2012 .

I was quite amiss in not defining the goals of my project.

After a few weeks away, and time to look through the thread, I now realize that that was a mistake.

So here 's the deal....

The goal for the project was to build a board that one could drop in as a direct replacement for the
original Issue One Sinclair board, but -> with upgrades if one wished to:

1} Add the necessary extra parts AND
2} Be willing to cut/modify the original case

BUT.....Still works as stock without 1 & 2 above.

It is also important (at least to me) to solve the USB keyboard problem. The same solution should
fit on the edge-card conn of a stock ZX before I can trust it in this design, anyway.

So... If anyone wants to lend a hand..I'm all ears. I just don't want to move too far away from
the 'roots' if you will. That's why I haven't bumped the RAM to 64k. There is little software written for
more than 16k so I haven't focused much on that area yet.

I would like to add every gooddie imaginable, but there's a limit - even with 4-layers .

Thanks to everyone for the help,
GTB

[siggi]

So... If anyone wants to lend a hand..I'm all ears. I just don't want to move too far away from the 'roots' if you will. That's why I haven't bumped the RAM to 64k. There is little software written for more than 16k so I haven't focused much on that area yet.

Hi GTB

welcome back

Yes, there are not too much programs, that use more than 16K ram. But there are a lot of programs, which run "around" the basic program: tools or assemblers or HIRES screens in address range 8-16K, machine code above 32K to load BASIC programs from MMC or USB-stick. And the block above 48 is sometimes used for bank-switching of more ram (the 1 MB ram card of the German ZX-Team, the 512kB ramdisk in my web-server). And battery-backuped ram at 0-16K is nice to play around with rom patches or new roms. So each more byte of ram is welcome

And have you noticed the SPONZY-thread? Perhaps your rom socket should be prepared for a 16 kB Eprom ...
Every new day gives new ideas, what could be done with a Zeddy

Siggi