Sinclair ZX80 / ZX81 / Z88 Forums

I was thinking about making a small PCB that uses 2 or 3 16 kB RAMpacks to create 32 or 48 kB RAM expansion. Maybe som jumpers could change the settings for the backport to be expansion or straight-thru port.

While this is a funny idea, please dont do it.
the original 16k rampacks draw too much current to have tree of them attached.
And be aware that the bus is not allowed to be like a star because its going to be flooded with reflections. Bus wires need to go go from port 1 to port 2 then to port 3.
Each 16 K rampack wants to be in the 16-32k area. It is difficult to modify the bus in a way that each of the three ports show a different portion of 16 K Adressing while the others will not be adressed.

Its so much easier to create a 56K or even 64K (disabling the ROM as well) RAMPACK with the help of one 64K RAM, 128K RAM 512K RAM chip.

kind regards
Paul

Thanks for your reply

I vaguely remember this been discussed many moons ago on the old ts1000 site... I can't seem to get the search to work I came up with some fairly simple decode logic and provided you could supply enough power no reason it shouldn't work.

Would be ugly as hell
3 X rampack wobble to contend with
Power usage

When you can use a single ram chip and simple logic , low power consumption, whybwould you not go with a more modern approach

Regards Andy

If you unpackaged the rampacks they could be stacked in a shallower configuration and back to back. I have project sketches for a stackable adaptation for the bus.

Personally I prefer to try and find out whether it does or does not work meaning find out what is needed to make it work.

Fish paper can be used to isolate the flexible electronics of rampack from each other after they are modified so they can go in same case.

Words of encouragement!

unpackaged the rampacks in back to back with shallower configuration, what you are trying is good. I would like to see your progress in this project. please keep us updates with pictures of your current doing.

I was advised not to do it as it will not work.

I am stoopid enough to try. Making a new decoder...learning the hard way!