BTW, I fiddled around some more with the PWM -> charge-pumped-Vpp idea,
    and it looks like with a single PIC, you could get both +V and -V
    outputs, separately adjustable, of essentially any voltage. Possibly
    reinvents the switcher, but adds only about 0.25-0.50 USD to the cost
    of an embedded system, and the Vpp levels are s.w./Rs-232 controllable.

It would be tough to generate a high enough current to program actual
EPROM based cells this way, right?  My understanding is that the flash
parts pretty much use the 12V VPP as a digitial input, while the EPROM
parts use it as an actual power supply for doing the programming...

BillW