PC's and EFI

[Thor Johnson]

I've been seeing a lot of references to the 4.77 MHz Basic Pontiac EFI
system lately,
and wanted to thow out a point that I think many have missed.  If I remember
correctly,
the author of that one used Basic to compute the new values and load them
into
independant PWM circuitry (I forget what he used, I think it was just a
triggerable,
settable counter).  The PC didn't run the tight timing loops -- it was
offloaded to
the set of counters.

Another important note goes out to those who want to use the joystick ports
for analog
inputs: They are slow resistance measuring devices.  To get a value from
them, you write
the bit to a zero, and wait until it becomes a 1.  The value is the time it
took to get
back to a 1.  I think the original design for the PC used a pair of 555
timers to do this.

A soundcard is a much better analog input (2 ch @ 21KHz), though
SoundBlaster cards have
terrible frequency response and linearity problems (at least for the
ears!)...

This isn't to say a PC based EFI is good/bad, I just wanted to point out
what I think are
some important points to consider.

-Thor Johnson

ps.  Someone tell me if these aren't formatted well.  I am trying Outlook
now instead of
     Pine.