wiki:geniuspc

Version 14 (modified by pulkomandy, 8 years ago) (diff)

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The Genius PC is a home computer from VTech. Released in the late 90s, it is one of the last microcomputers. Not very much about it is known, the computer doesn't come with any useful hardware documentation and the integration of everything in a big ASIC makes it hard to know how it works.

Moreover, this computer have different names in each country, making it even harder to track down the information.

  • France : VTech Genius PC
  • Germany : VTech Genius IQ 128
  • UK : VTech IT Unlimited
  • USA : VTech Precomputer Unlimited
  • Also mentioned on the french packaging : Switzerland, the Netherlands, Canada.

Hardware :

  • Motorola MC68EC000, 16-bit external databus, 32MHz
  • 256K of RAM
  • 2M of ROM - Sharp LH537NWN mask ROM
  • Mass storage : 128KB flash memory - AM29F010
  • Cartridge port, apparently on memory bus with system ROM and storage flash. The french system comes with cartridges only containing straps, likely shorting some pins enable extra features...

The ROM is a 16-bit one, available directly on the CPU bus. The FLASH is 8-bit, but directly on the CPU bus as well. The cartridge port is connected to the same bus, and can be used for extra flash storage.

Both flash chips (internal and cartridge) are 8-bit only. This means they can't be used for executable code.

The RAM is accessed through the VTech 27-05793 chip, which likely handles memory refresh. I don't know if the RAM is mapped as 16 or 8-bit to the CPU, and if there are any wait states when accessing it or whatever. The VTech chip might also have some internal memory ?

Other chips

  • BH7236AF : Video encoder (PAL/NTSC + RGB output). On french motherboard RGB is used, composite is not wired.
  • LMT324 : LM324, used as audio amplifier
  • C807U : Toshiba microcontroller. Handles mouse and keyboard scanning, LEDs, on/off buttons, etc. Running at low speed out of internal RC oscillator, as there is no external crystal for it. Seems to communicate with the VTech chip through a serial link.
  • VTech 27-05793 : of course a datasheet of this one would make things easier. Seems to be also called "LS05PR730C102" ?

Output : RGB color video (french version, others have composite output) and mono sound.

Color palette is at least 15 colors :

  • White
  • Light grey
  • Dark grey
  • Black
  • Sky blue
  • Blue
  • Red
  • Green
  • Dark green
  • Yellow
  • Orange
  • Brown
  • Dark brown
  • Mauve
  • Pink

(the 16th color is likely "darker-than-black", used for blanking ?)

Resolution seems to be something like 480x200. This makes a 48K framebuffer. Top and bottom borders can have different colors.

Serial port

Turns out the serial port is standard. 9600 baud, 8N1, no control flow. You can connect with minicom and use the "chat" application. Files are transferred using the XModem protocol.

This means text is encoded in ASCII. Makes it easy to look for them in the ROM dump.

Rom DUMP

With the help of an AT90USBkey a dump of the ROM was made. You can download it in the attachment section below. The rom is 2MB big, but there is a big chunk of it which is actually text, graphics and audio sample, and disassembling the remaining 68000 code should not be too hard.

For now I only have the French ROM, but people are going to send me the German and UK ROM chips so I can dump them as well (thanks guys !). If you have other info about the hardware, let us know !

MESS core

I'm in the process of writing a MESS driver for this machine. So far it has the CPU, ROM and RAM (that was the easy part). Now I'm trying to figure out the memory mapping and the use of the hardware registers, as well as studying the ROM code and trying to understand how it works.

Attachments (9)