Nude Bender on Futurama

[Karlos]

:lol:

I've still got some Z80 and Z80-180 evaluation kits somewhere.
The z80-180 is pretty cool. Runs at (gasp) double digit clockspeeds, has multiply and divide instructions (unlike its' predecessor), has an MMU supporting a meg of page mapped memory, on board UARTs etc.

At one point a friend and I were hell bent on an 'upgrade' design for the speccy that would use the z80-180 at 10 MHz and an eeprom containing a reassembled version of the original basic rom with various improvements built in. We wanted a 1Mb speccy, complete with task-switching kernel that supported an 'emulated' 48K mode. Never finished the design though :-(

[Karlos]

@bloodline

The 48K speccy's rear expansion slot was pretty much total CPU bus access. You could basically get at all the original IO lines and thus supplant completely the original CPU without having to remove it. Or so the theory goes. The design was to make a module that would sit on this bus and use it to access the various logic and video circuitry (such as it was :lol:) and basically do everything else on the module. 1Mb DRAM (we had 256KB to start with) with the first 64K mapped from the eeprom at startup.

The user programming model was very similar - you still only get to see 64Kb at once, but each 4K page can be anywhere in the 1Mb space. Better still the z80-180 was available up to 20+ MHz. Even at 10MHz it was more than 5x faster than the 3.5 MHz z80 in the speccy itself (a combination of higher clockspeed and better instruction timings).

My mate (a proper electronics whizz) was investigating using a cheap&nasty PAL video encoder chip from maplin (TEA2000-v1) on the thing that would have made 6-bit (wow, 64 colours!) colour possible which would have been more than feasable with the amount of RAM available. The chip generated PAL compatible composite output directly, which was handy. We did managed to get a test screen from the evaluation system using it :-D

Of course what we were ending up with was a new computer with a spectrum keyboard and tape interface :lol:

I wonder were all the schematics are now?