I found out a little more today on the HP Z4 G4. Userbenchmark reports the same MB part# for both CoreX, and W Xeon benchnarks. Since it's a workstation I'n guessing the BIOS allows both, but for a workstation the C422 chipset would be expected.. Dell used the X299 chipset for their Core X versions. Probably the better choice for an overclock.
Unclewebb hasn't tested this family of CPUs with Throttlestop. Intel XTU may be the way to go. But it might not want to play with a C422 chipset.
I've reached out to some HP overclockers, and some unlocked Xeon fans to try and get some more info. on this.
Throttlestop was written by Unclewebb for undervolting/ underclocking laptops for extended battery life. Then some wiseguys found out it could also overclock locked BIOS computers with unlocked CPUs. In my case I went from 0% overclock to 2nd and 3rd place at CPUZ with a QX6800 in a totally locked down Dell Dimension E520. Beginners luck.
http://valid.x86.fr/bg4n0r
That's about as far from an undervolted laptop as you can get! He's been following the OC projects in various forums, and participating here with the T3500 projects. It really isn't fair to expect him to run out and buy a system just because someone (like me) asks some questions here. I did my first one w/o any help from anybody. Since I had just about no computer skills to speak of that says a lot about how easy this can be.
So thanks to Unclewebb for making this possible.
Looking into this further HP notes in their datasheet for the Z4 G4 two different chipsets for the differnt CPU families.
The Core X runs the X299 chipset that allows overclocking. The W Xeons C422 that doesn't. Memory type and capacity differs also.
So what does that mean to us? IDK yet. Typically Xeons that match an unlocked CPU are unlocked too.
So IDK if this is a hard separation or not. Also IDK if it matters to us. TS might OC the W Xeon, chipset or not, if it's unlocked.
I'll see if I can get the HP guys interested in this. But it does look like there are Dell and HP workstations with an unlocked CPU and an unlocked Chipset out there