Originally I was just going to post my numbers, but while I was trying out different settings to get more sets, I noticed some patterns I wanted to look at. Here's my theory:
I haven't looked at Z at all, and not much at Y, but I'm almost certain X and Y are sets of bitflags (I think probably Z too). That is, if you convert the numbers to binary, each bit represents a flag. 1 for on, 0 for off. It's about 7am and I haven't gone to sleep yet, so I'm going to make this quick and post what I've got so far and do some more tomorrow.
I'll describe them as:
X1X2 - X3X4
that is, X byte 1, X byte 2, etc.
And the flags I'll refer to as
X1.1 - 8
that is, X byte 1, flag(bit) 1 - 8.
Guesses so far:
X3.1 - IP Setup correctly
X4.4 - No cable detected
X4.5 - DNS Failure (set if both OR either DNS fails)
X4.6 - Manual IP config?
X4.7 - Cable detected, but not working
This would explain why working connections always seem to have X3 at F*. F means all four first flags are set, which appears to indicate success in those four areas. IE, in my test where I gave it the same IP as my PC and got an IP conflict, I got an X3 of 08, which means none of the first 4 flags are set. The only time I've seen flag X3.1 not set is when it can't get an IP.
Btw, fuzzy, did you actually get an X3X4 of F021 like you've used in your examples? If so, what was your setup? I've haven't seen X4.3 set and the X4s are what I've got the most on.
If anyone has info that doesn't fit with my theory lemme know, this is just what I came up with off no sleep at 7am
I'll post some of my more interesting numbers/conditions for you tomorrow fuzzy.