SDH,
Thank you very much for your reply. I took your suggestion and did a Google image search. It turned up the photo you posted from an eBay listing, as well as some others that show a PCH heatsink. For example:
Also, going to the HP Customer Self Repair Services Media Library
http://h20464.www2.hp.com/index.html
and selecting:
Category: Desktops & Workstations
Product family: Personal Workstations
Product series; HP Z230 Small Form Factor Workstation
and then Remove/Replace videos finally directs to a page for the Z230 SFF:
http://h20464.www2.hp.com/results.htm?SID=5367813&MEID=AB9BA2FA-A355-4C16-90A8-B7FFAE07F88C
Clicking the "RTC Battery" link at left, going about a quarter of the way into the video, and looking at the bottom right corner of that image shows the corner of a heatsink on top of the PCH.
Maybe HP built some Z230 SFF motherboards with a PCH heatsink and some without? Or maybe the PCH heatsink is a separate part number that gets added to the motherboards that appear for sale on eBay?
I'm still surprised not to find a PCH heatsink in mine. I've built a couple of machines using Supermicro X10 motherboards with C23x PCH. Those came with PCH heatsinks, which do get hot.
If someone with a Z230 SFF can take a quick look inside and let me know whether your PCH has a heatsink that would be awesome.
Thanks,
Frank