Hi,

Today I received an interesting piece of hardware.

It is a Nintendo Demo Boy II, which is a store demo unit for the Game Boy. A
modified Game Boy plugs into the box, and the GB picture appears on the TV
which connects to the unit.

What has this got to do with the NES? More than you might expect...

The unit is housed in a beige-coloured metal box, and plugs into the mains,
100-240VAC. Inside the case there is space for two boards, which would allow
two Game Boys and two TVs to be connected. Only one board is fitted in my
unit.

The Game Boy connects to the Demo Boy II via a 10-way ribbon cable. This cable
also supplies power to the Game Boy. During play, the GB game is also visible
on the GB's LCD screen. Adjusting the GB volume control adjusts the TV sound
volume as well as that from the GB internal speaker. On the TV screen there is
a border around the GB area, similar to one of the borders of the Super Game
Boy (the one which looks like the GB screen surround).

There are DIP switches on the board to set a timeout, after which the GB will
be reset.


The most interesting thing about it is that the unit is based on NES
technology! There is a NES CPU, PPU and MMC5A on the board, and a NES type RF
modulator section.

Apart from the CPU, PPU and MMC5A, a PAL (AMPAL20L10APD) is the only non-
standard chip on the board. All other chips are either SRAMs or standard
74-series logic. There are 33 74-series ICs, one 16Kbit SRAM, and five 64Kbit
SRAMs.

There are 64Kbit (8Kbyte) PRG and CHR EPROMs on the board. Their windows are
covered with labels that read:
        DV-PRG            DV-CHR
         U-47     and       U32
        REV. B             REV A

Text on the board reads:
        DEMOVISION
        PN 22930 REV B

My unit must have been made quite recently; several chips have date codes in
1994 or 1995.


Does this mean that Nintendo could have brought out a Super Game Boy-like
device for the NES? Well, it may well be possible to make a cartridge for the
NES that functions like the Demo Boy II. That is, a modified GB would plug
into this. Such a cartridge would need to connect to the expansion port on the
underside of the NES for the audio input.

A more complex cartridge may be possible, incorporating the GB CPU and hardware
to allow the NES controller to be used.


(I seem to remember reading something about a "Wide Boy" which plugs into a
Famicom to play GB games on a TV. Does anyone remember reading about this?)



I made up a .nes file of the Demo Boy II PRG and CHR data (PRG data had to be
doubled because of the minimum PRG size of the .nes format). Set as mapper #0,
the GB border is displayed. This is not of any real use.

If you do any testing on this image, remember that the Demo Boy II uses an
MMC5. I would like to know what addresses the program accesses -- this should
shed some light on how the MMC5 is used. I expect its EXRAM feature is used.


Finally, I can write down the Nintendo part numbers for single or dual US,
European or UK versions of the Demo Boy II if anyone is interested. Maybe it's
still possible to buy Demo Boy IIs from Nintendo???


-- Mark