mjmahon@aol.com (Michael J. Mahon) writes: >Matt Jenkins wrote: >>On Mon, 08 Dec 2003 19:20:40 +0000, Michael J. Mahon wrote: >> >>> I'd always wondered why the PAL Apples had the AUX slot in line >>> with slot 3--picking up -12v sounds like the answer. >> >>That's the answer, but the machines aren't actually PAL; The video >>frequency has been changed to 50Hz, but the color-burst signal coming >>from the board is the same quasi-ntsc signal generated by US Apple II's. >>The was a modified extended 80 column card for Euro standard markets >>that delivered a PAL signal on a seperate connector on that card. Once >>the platinum IIe was released these became unavailable as the platinum >>IIe shipped with the same minature card here as in the US. Additionally >>Apple's Composite Colour monitor was capable of generating a colour >>picture from the 50Hz Apple's. Although for some reason the pre-platinum >>Euro boards produce 'wrong' colours from their composite port when >>connected to this display (which is I think the real reason the fancy >>80 column card was created) >> >>One thing that's really frustrating these days is that even with >>multi-mode tv's that support either a PAL or NTSC signal, you still can't >>get colour out of the Euro models on a TV set, as most of them seem to >>assume a PAL signal because of the 50Hz refresh. On the original II and >>II+, the 50 Hz version is created by cutting special pads on the >>motherboard (and maybe some other things, can't remember right now, it's >>in the Apple II Reference manual) so you can at least reverse it and >>create a real 60Hz ntsc signal. Unfortunately there's no easy way to do >>this on a IIe. The IIe motherboard used in PAL countries (like Australia, UK etc) was released in two main versions: "PAL" Rev A/B used in beige IIe. Uses a 50Hz IOU chip and a 14.25MHz main clock (instead of the 14.31818MHz main clock on an NTSC board. It has the equivalent of the PAL color card (used in EuroPlus Apples) integrated on the motherboard. The PAL color circuit has a 4.43MHz color burst crystal and a resistor network attached to a shift register to convert bit patterns into the appropriate PAL color (but not perfectly - the colors are noticably different from those on an NTSC Apple II). "International NTSC" used in Platinum IIe. Uses same 50Hz IOU and slower main clock just like the above but does not have the PAL color card integrated onto the motherboard so you cannot just plug the output into the A/V socket on a PAL TV. I guess the Aux Slot + Slot 3 video card was designed for this board as it would not have been needed on the earlier model. >ISTR that Apple just changed the vertical frequency, but left the color >burst (and implicit subcarrier) at the NTSC 3.58MHz. I suppose that >a main crystal change could bring the burst frequency to the PAL >standard, by shifting the frequency of everything a bit. You cannot just change the main clock from 4x NTSC to 4x PAL color burst as that would be a 23% speed increase which would break timing critical code like the Disk ][ driver etc. Also PAL alternates the phase of the color burst on adjacent lines so the colors would not work either. I actually have a 60Hz IOU chip in one of my PAL IIe systems as otherwise the Meg80z 1MB Aux slot RAM card gets the first 7 pixels in 80col/Double Res Graphic modes from the wrong bank of memory. -- David Wilson School of IT & CS, Uni of Wollongong, Australia