If you would see this ZX81" the first time, you wont believe your eyes. We call it ZX96 (not the ZX97 - this is Wilf Righters project- completely different!).
Basically we use another connector system with 64 pins in two rows, known as the DIN..... connectors. The pins are wired like the old ZX connector so you can use the PCBs also with ZX connectors.
As a base system we have added to an usual ZX81-PCB a new memory-system called the GIANT, which enlarges the amount of memory up to 144 kBytes!
But the advantage of the ZX96 are the expansion cards! We have a disk controller for 3,5" single-sided disk drives, which will give you 160kB per disc. An improvement will soon be available for double-sided drives and a disc format which is compatible to the ZX-Spectrum and to PC.
The Multi I/O card has not less than three PIOs and two RS232 ports. You need this to connect centronics printer (bubble-jet also!), modem and others.
We also solved the keyboard problem. There is an keyboard card, which connects an usual AT-keyboard to the ZX81! Because there was enough space on this PCB we added a video output for true or inverse video on a real Video monitor. For TV you can place a modulator on this PCB too and get so inverse video also on TV.
Modern computers have always harddisk drives, so the ZX96 has one too. This is the latest project we finished, with an extraordinary DOS!!
And at last the Megabyte-card gives you additional 1MB or even 4MB of RAM if you need.
PCBs available: for all of the above projects we designed 160x100mm PCBs, produced in the highest possible quality. There are only a few pieces left!
If you need more information about the above projects or if you are interested in the PCBs - don't hesitate to contact me: mailto: kai.fischer