HP Zbook 15 G1 - Dual-Core to Quad-Core i7 CPU Upgrade Possible?

[pixelado_x64]

tl;dr: Has anyone tested upgrading a dual-core Zbook 15 G1 to a quad-core CPU?

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So, as the title goes, I currently own a Dual-Core Zbook 15 G1 which came factory-equiped with a Core i7-4600M CPU (2c4t).

I'm currently planning to upgrade it with a 4800MQ or a 4900MQ (both 4c8t) if possible.

Here's the thing, though: The service manual for this particular model lists different system board assemblies for dual-core (SPS: 734303-XXX) and quad-core (SPS: 734304-XXX) computers. A quick visual inspection of pictures found online tells me the only obvious difference is the lack of the two additional RAM slots under the keyboard[1], which I guess makes sense as a dual-core CPU would probably not be able to "see" the two extra DIMMs.

I could buy the desired CPUs off Ebay but most sellers won't accept returns in case of incompatibility, as that's the buyer's fault. It would be a shame to spend close to $100 in a CPU only to find it the computer isn't up for it!

I have looked hard in the local market but the best I could find is a Core i7-4710MQ, which is a bit slower than the 4800MQ and it lacks VT-d[2]. They're also asking about $150 for it so yeah, it's overpriced.

So, here's the big question: Has anyone been able to perform a dual-core to quad-core upgrade on this particular system? Or something similar? I guess there's been people would have tried to upgrade their dual-core Sandy Bride/Ivy Bridde EliteBooks to quad-core CPUs as well haha.

I've read about people successfully upgrading their dual-core mobile workstations but they were from different brands, most often Lenovo ThinkPads.

Thanks in advance for your time!

Regards.

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[1] Which I fully expected to get when I purchased this machine in used condition, **bleep** dishonest sellers!

[2] Which I plan to use for GPU pass-through under Linux.