A project log for V-Tech Genius Leader / PreComputer Hacking

Turning a toy into a hardware tinkering platform

Bernhard Bernhard "HotKey" Slawik 05/16/2020 at 21:351 Comment

The other day, I decided to do something "completely different" for a change. So I went to my wall of VTech Genius Notebooks and grabbed a random one from the pile that had the same cartridge port as the 4000, but a larger screen.

My pick: the Genius Leader 6000SL aka. Genius PreComputer Prestige.

This time around I wanted to cheat a bit, since I didn't want to spend another 2 years analyzing it (as I did with the 1000/2000/4000 series). Instead of building a debugging cartridge and finding all the memory and port mappings myself, I just searched for some emulation source. And I found a driver in the trusty old MAME repository (src/mame/drivers/prestige.cpp). It is missing some functions (printer port, sound), but the basic stuff is there.

First thing that sparked my interest: The machine seemed to use a DMA based LCD (240x100, graphical), so there is no need for weird LCD initialization code and software frame buffer stuff. It's as simple as poking bitmap data into memory at 0xE000-0xEBB8 and it gets drawn on the screen automagically!

The keyboard is also pretty straight forward (matrix at ports 0x40, 0x41, 0x42) and didn't take much effort to get working. And even the mouse (yes, it has an external mouse!) is directly mapped to ports 0x04 and 0x05 for the X and Y positions. Nice!

I must say, I am quite impressed about how much easier it is to work with the 6000 compared to the 1000/2000 and 4000 series. It took just one day to write my first "Hello World" from scratch (including custom font rendering). I would call that an "instant gratification" :-)

The bank switching / memory mapping in the Prestige is also quite nice: It allows for the cartridge to be mapped to lower memory at address 0x0000. This means that a CP/M style system could run on that machine without any hardware modifications (i.e. no "Chip Select hack" needed)!

So maybe I'll just give it a try and create a Plug & Play CP/M cartridge for that machine!

Stay healthy!

Update: I have updated the VGLDK Github repository to allow compilation against the new "gl6000sl" target. Cheers!


Jonson26 wrote 05/24/2020 at 14:17 point

That's the one I have! I will definitely try to build that catridge as soon as you release some schematics. (I do have another cartridge as a connector donor.)

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