problem with cpu usage

Version of Windows?

Right-click System on that list in Task Manager, and select Properties.  If it says ntoskrnl.exe in box at top of the General tab, close Task Manager and try the following:  

1. At desktop, open a CMD prompt window, Run as administrator
2. At the prompt, type in: chkdsk c: /r and press Enter. Accept offer to run chkdsk at next boot and reboot PC.  chkdsk will run before Windows loads so be patient.  When you're back at desktop, look at the chkdsk log to see if there were any "unfixed" errors.
3. Assuming no "unfixed" chkdsk errors, at the desktop, open CMD window again as in #1
4. At the prompt, type in: DISM.exe /Online /Cleanup-image /Restorehealth and press Enter. Include a space in front of each / and note any error messages when that's done.
5. Assuming no "unfixed" errors in #4, at the CMD prompt, type in: sfc /scannow and press Enter. Include a space in front of the / and note any errors when that's done.
6. Assuming no "unfixed" errors in #2, #4 or #5, reboot PC and check System for its CPU usage in Task Manager

@RoHe​  i  have. Windows 10

thank

but the   cpu usage 20% remain

Is Win 10 fully up-to-date on your system?

Does the listing for System in Task Manager show ntoskrnl.exe as the process that's running?

Did chkdsk, DISM and sfc all run without reporting any "unfixed" errors?

How much CPU time was System using before you did the BIOS update? What version of BIOS was previously running when you didn't have the high CPU usage?

How much CPU time does Task Manager show for Runtime Broker after running those commands?

Have you scanned thoroughly for malware lately? Malwarebytes (free) is a good tool for this.

Since this BIOS update is new, it's possible it has some issue or possibly just didn't get properly installed.  It's always safer to do BIOS updates entirely outside Windows using a USB stick and the F12 menu Flash Update option, rather than letting SupportAssist or Windows Update install them.

You might want to try reverting to the previously installed version of BIOS by doing a BIOS Recovery.  Go to the page listing the BIOS 1.23.0 update and click Older Versions. Click the version that was running previously, if you know it, or click BIOS 1.22.0. When the page opens, download the BIOS Recovery Image File (.rcv) for that version (not the .exe file).

Save the .rcv file (don't change its name) on an empty (non-bootable) USB stick, 2 GB (but not more than 8 GB), formatted FAT32. Then follow the instructions to do a BIOS Recovery carefully.

It would be a really good idea to image your entire boot drive before running the Recovery, just in case.  You can use any imaging tool you want, eg Macrium Reflect (free for 30 days), and save the image on an external USB drive. That way you'll have a backup...

@RoHe​ 

thank for reply 

Run  chkdsk, DISM and sfc  dont    show any problem

i receive the bios update  from   support assistant  in 21/12   and  the  22/12  morning  i  notice the usage cpu  20%   before  the  usage  cpu was  3-10  idle 

maybe is the problem of  the windows  not the bios

my system have receive  many bios  update in  past without problem 

I  check  for virus with eset  and i find   three  virus   after   delete  them

the  malware byte    don t  find anything 

i don t  take the risk to  make o recovery  bios  now because  i need the  pc

George

@RoHe​ the  file  in   task manage is  ntoskrnl  i  check that

I   run     eset  again   and   i find   4   virus

i   clean  again  with eset...   and  a  second    a scond scan     the system is  clear

Just because you've done BIOS updates in the past, doesn't mean the latest one doesn't have a problem and/or it didn't get installed correctly. That's why I suggested you do a BIOS Recovery, with a previous version where CPU usage wasn't so high.

So you had malware on this PC...  You might want to run another scan with SuperAntiSpyware (free) to check for malware the others may have missed. And you may want to (temporarily) disable Eset, if that's what you use normally, and activate Microsoft's built-in Windows Defender and have it run a full scan too. The more scans you run, the higher the odds of finding/removing any remaining malware.

BTW: Has the CPU usage gone down since you've run the scans and removed some malware?

hi

after  remove  the  virus   with ESET  the  cpu usage remain  20|%

Did you try running SuperAntiSpyware and Windows Defender, in case Eset and Malwarebytes missed something? 

I run. Window's defender  find. Twop. Virits  that clean 

I. Make a new scan with. Defender  and. The system wan cleat 

How did you get so much malware on this PC?

You may want to run chkdsk, DISM and sfc again (as above) to make sure everything is ok.

If that still doesn't solve the CPU usage issue, you may want to run a BIOS Restore using a previous version of the G5 5090 BIOS...

Maybe. A. Winduws. Upadate solve. The. Problem.