HP Z400 keeps on disabling Hyper-threading when I turn it on in BIOS

[Ilegal_Banana]

Hey,

Basically when I go into task manager i only see logical processors as 6 and core count is 6 for my HP z400. I have the intel xeon w-3680 which has 6 cores 12 threads but only displays 6 cores 6 threads in task manager, I found out this was due to hyper threading being disabled in BIOS but when I went to change it, it keeps changing back to the disabled setting.

[savvy2 · Accepted solution]

a simple BIOS and CPU xeon issue.

is your BIOS updated? i bet not or you CPU is not authorized by HP or wrong CPU installed. or not reset correctly.

first tell what CPU is there,  real intel  p/n; ok you did thanks.

my Z600 uses CPU E5675

then go to intel.com see 1st page of your hyperthreading y/n it is yes

yours is here

https://ark.intel.com/content/www/us/en/ark/compare.html?productIds=47917

w3680  i see  x273 persons doing it here. benchmark pages.   so wrong version BIOS or not doing full pC reset after changing out RAM or CPU.  do you know how?

https://www.userbenchmark.com/System/HP-Z400-Workstation/67

• fully turning off PC with  button push long. time.  10 seconds.
• pull line cord AC now .
• reset it for one hour
• Ok AC back push power.
• then look inside BIOS again.

fails, then remove RTC battery  , NO AC power, at all , let it sit   awhile, test battery if good put it back

now BIOS is reset and well learn new parts, like RAM or CPU fully.

seen this many times BIOS tells fibs but reset it always works. (BIOS upgrades notwithstanding)

if still fails.

so wrong BIOS version or this CPU is not HP authorized or the RTC coin cell battery is marginal

RTC below 2.9vdc is NO GOOD.

[Ilegal_Banana]

Yes Hi, 

Thank you so much for the fix, I went ahead and followed your instructions on the BIOS since I only got this computer recently, and found out that it still uses the old BIOS by hp from almost 2011, I then downloaded the new BIOS from the official hp website for the z400 and it fixed the problem for hyper threading and probably other issues that I had (Yet to check). Thanks in advance.