Re: Apple II EUROMOD EUROPLUS, part numbers, etc.

[Linards Ticmanis <ticmanis@coli.uni-sb.de>]

Mark Cummings wrote:

> I guess yes it could. possibly the ROM was the same already, only I modified
> mine to accept lowercase input. As far as I know the euroPlus was just 240V
> 50Hz power.

Confirming. The ROMs were identical to the American II+. The difference
was in a) the case label,  b) some pad jumpers on the motherboard and c)
a very slightly slower frequency quartz (which is almost impossible to
get now, I think it was 14.025 MHz or so.)

This gave you a "sorta-NTSC 50" picture, i.e. the usual PAL 50 Hz 625
line beast but with sorta-NTSC color encoding. Just "sorta" since the
quartz was too slow. If you wanted to use a color monitor you had to add
the PAL interface in slot 7.

I have a 3rd-party PAL interface that has an onboard RF emulator in
addition to the video output so you could directly attach a TV set. Most
TV sets back then didn't have any inputs except for RF/Antenna in
Europe. I don't know if the original Apple PAL interface also had an RF
emulator on the card.

The PAL board is not a universal NTSC-to-PAL converter, it depends on
the way the NTSC signal is created in the Apple II hardware. The reason
you needed an extra card was that the Apple's video out circuit was
designed around the NTSC spec in a rather ingenious way (by creating a
finished chroma/luma signal without first creating separate chroma and
luma) that can't simply be transferred to PAL without causing major
software incompatibility. So the card basically had to take apart the
chroma and luma info with the help of a shift register of sorts, mixed
PAL's U and V components with a simple 2 resistors for each of the
Apple's 4 "basic colors" (lowres COLOR=1,2,4,8), and then it used a
cheap PAL-DE(!)coder chip but fed it "backwards" to encode PAL instead.
A rather clever trick.

-- 

Linards Ticmanis

 The Master said, "The business of laying on the colors follows the
preparation of the plain ground."