I am testing BOINC (above v6.1) on the Linux machine with two 12-core cpus (total 24 cores).
I set the preference file (global_prefs_override.xml) for 100% full cpu-loading as the following:
<max_ncpus_pct>100.000000</max_ncpus_pct>
But only 16 WUs are working on my system.

I got same result for the following setting.
<max_cpus>24</max_cpus>
<max_ncpus_pct>100.000000</max_ncpus_pct>

Is there any limitation of multi-core or multi-cpu?
If not, please let me know what is the optimal setting of preferences.

Many thanks for your help.

Which BOINC version are you using explicitly? "Above v6.1" isn't giving much of a clue. After you set the preferences override file, did you restart BOINC, or make it re-read the prefs file?

BOINC Manager->Advanced view->Advanced->Read local prefs file.
Or using a command line, navigate to where BOINC stores its files, then type boinccmd --read_global_prefs_override

Can you use the GUI (BOINC Manager)? If so, can you set the preferences through Advanced->Preferences (or when using a BOINC 6.12 version it's in Tools->Computing preferences)?

---

This is very much the same issue that I have been having. However, I run Windows 7 x64, WCG 6.10.58 and this seems to be an intermittent issue.
I have seen 13 cores used and at other times 16 cores used when this has happened. Checked on it later and all cores are utilized.

Temps are fine and I have restarted both BOINC and the system. When the BOINC restarted 13 cores were running. Next time I checked hours later, 24 cores running. Plenty of jobs in queue.

I have found only one way to "correct" the problem but it only temporarily corrects the malfunction. If I Advanced>Shut Down Connected Client, on restart all cores are used again. However, this does not prevent the failure from occurring again.

Thank you for any assistance.

Global_Prefs:
<global_preferences>
<run_on_batteries>1</run_on_batteries>
<run_if_user_active>1</run_if_user_active>
<run_gpu_if_user_active>1</run_gpu_if_user_active>
<suspend_cpu_usage>0.000000</suspend_cpu_usage>
<start_hour>0.000000</start_hour>
<end_hour>0.000000</end_hour>
<net_start_hour>0.000000</net_start_hour>
<net_end_hour>0.000000</net_end_hour>
<leave_apps_in_memory>1</leave_apps_in_memory>
<confirm_before_connecting>0</confirm_before_connecting>
<hangup_if_dialed>0</hangup_if_dialed>
<dont_verify_images>0</dont_verify_images>
<work_buf_min_days>0.000000</work_buf_min_days>
<work_buf_additional_days>5.000000</work_buf_additional_days>
<max_ncpus_pct>100.000000</max_ncpus_pct>
<cpu_scheduling_period_minutes>60.000000</cpu_scheduling_period_minutes>
<disk_interval>1500.000000</disk_interval>
<disk_max_used_gb>50.000000</disk_max_used_gb>
<disk_max_used_pct>50.000000</disk_max_used_pct>
<disk_min_free_gb>50.000000</disk_min_free_gb>
<vm_max_used_pct>70.000000</vm_max_used_pct>
<ram_max_used_busy_pct>80.000000</ram_max_used_busy_pct>
<ram_max_used_idle_pct>90.000000</ram_max_used_idle_pct>
<max_bytes_sec_up>100003.840000</max_bytes_sec_up>
<max_bytes_sec_down>100003.840000</max_bytes_sec_down>
<cpu_usage_limit>100.000000</cpu_usage_limit>
<daily_xfer_limit_mb>0.000000</daily_xfer_limit_mb>
<daily_xfer_period_days>0</daily_xfer_period_days>
</global_preferences>

BOINC Startup

1/27/2011 5:15:41 PM Starting BOINC client version 6.10.58 for windows_x86_64
1/27/2011 5:15:41 PM Config: report completed tasks immediately
1/27/2011 5:15:41 PM Config: use all coprocessors
1/27/2011 5:15:41 PM log flags: file_xfer, sched_ops, task
1/27/2011 5:15:41 PM Libraries: libcurl/7.19.7 OpenSSL/0.9.8l zlib/1.2.3
1/27/2011 5:15:41 PM Data directory: C:\ProgramData\BOINC
1/27/2011 5:15:41 PM Running under account User
1/27/2011 5:15:43 PM Processor: 24 GenuineIntel Intel(R) Xeon(R) CPU X5670 @ 2.93GHz [Family 6 Model 44 Stepping 2]
1/27/2011 5:15:43 PM Processor: 256.00 KB cache
1/27/2011 5:15:43 PM Processor features: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss htt tm pni ssse3 cx16 sse4_1 sse4_2 nx lm vmx smx tm2 dca popcnt aes pbe
1/27/2011 5:15:43 PM OS: Microsoft Windows 7: x64 Edition, (06.01.7600.00)
1/27/2011 5:15:43 PM Memory: 16.00 GB physical, 31.99 GB virtual
1/27/2011 5:15:43 PM Disk: 278.77 GB total, 221.30 GB free
1/27/2011 5:15:43 PM Local time is UTC -7 hours
1/27/2011 5:15:44 PM NVIDIA GPU 0: GeForce 8400 GS (driver version 26658, CUDA version 3020, compute capability 1.1, 488MB, 22 GFLOPS peak)
1/27/2011 5:15:44 PM NVIDIA GPU 1: Quadro NVS 295 (driver version 26658, CUDA version 3020, compute capability 1.1, 231MB, 21 GFLOPS peak)

Windows log of CPU going idle:
- <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
- <System>
<Provider Name="Microsoft-Windows-Kernel-Processor-Power" Guid="{0F67E49F-FE51-4E9F-B490-6F2948CC6027}" />
<EventID>26</EventID>
<Version>0</Version>
<Level>4</Level>
<Task>4</Task>
<Opcode>0</Opcode>
<Keywords>0x8000000000000000</Keywords>
<TimeCreated SystemTime="2011-01-28T00:15:27.760474200Z" />
<EventRecordID>7108</EventRecordID>
<Correlation />
<Execution ProcessID="4" ThreadID="64" />
<Channel>System</Channel>
<Computer>beast</Computer>
<Security UserID="S-1-5-18" />
</System>
- <EventData>
<Data Name="Group">0</Data>
<Data Name="Number">12</Data>
<Data Name="IdleStateCount">1</Data>
<Data Name="PerfStateCount">0</Data>
<Data Name="ThrottleStateCount">0</Data>
<ComplexData Name="IdleState">01</ComplexData>
<ComplexData Name="PerfState" />
</EventData>
</Event>