Little spy told me there might be a new Zeddy on the horizon

[siggi]

I decided to stuff all the memory on this side of the fence so that I can have UDG.

But then you can't have WRX HIRES there (at least with the "normal" ULA) ...

Siggi

[Andy Rea]

Looking good C

It's fairly easy to get the switching of udg/wrx done in the CPLD ula. i have one of mine set so that the 8-16K can be either, and above 16K is always wrx.

Andy

[Paul]

I've settled on a memory board design. The RAM and EEPROM are sitting in the original ROM socket. It means that I have to implement a paging scheme in the ULA as there are only enough address lines to give me 8K banks. The EEPROM has a spare line and the RAM has 4. Currently they're all grounded so I'm stuck with 8+8K.

I decided to stuff all the memory on this side of the fence so that I can have UDG. The RAM will also be able to replace the ROM so I can run SPONZY

You can see the carefully drilled hole in the board which accepts the mounting post in the case. Nasty, but it works.

ultra-mem.jpg

It's currently a little too tall and the front edge of the chips foul on the slope at the front of the case so I'll either work on a 4th prototype with the chips set back a little, or remove the sockets or file down the chip's package :¬.

Hopefully in the next couple of days I'll have the ULA paging the RAM and ROM.

Hi Charlie,
did you consider to put the chips on the other side of the CPU, probably upside down, plugged into the ROM-Socket?
There is plenty of room there, or do you reserve this for your internal ZXPand?
Kind regards Paul

[sirmorris]

Hi Paul,

I've tried various orientations of the chips and I may well go back to the upside-down version for the last prototype. The space to the right of the processor is reserved for this

zxpand-inside.png (11.43 KiB) Viewed 1879 times