gnupic: Thread: ICSP with PIC18F4550

I've been trying to do low voltage in-circuit serial programming of an
18F4550 with a direct connection from the parallel port to the pic chip.
Why? Well, mostly because this is how I've been programming PIC16F874's
for a few years now (using prog84, mostly).

I've been experimenting with this using a short C program.

To make my first tests as simple as possible, I thought I'd try to read
the device id from the chip. There is sample code in programming spec
pdf for this, and it makes sense, and I think I've copied it correctly.

I look at the MCLR, PGM, PGC, and PGD signals on the scope and I think
they look right.

But its not working. I'm just wondering now:

1. The timing parameters (for things like data setup before clock
falling edges) are only given minimum values. I'm certainly meeting
these minimums; but maybe there are maximums I'm outside of. Has anybody
bumped into this before?

2. As the 18F4550 chips come from the factory, they don't need crystals
connected to be programmed, do they? As I see it, the internally timed
operations (like bulk erase) should be timed by an internal oscillator.
But I was hoping someone could confirm that if they've looked into it
before.

Any tips or suggestions would be appreciated.

Ben