I have a dual quad-core processor, but only 4 cores are being utilized by the latest x64 Windows builds(5.10.13 and 5.10.20). In a previous build (5.10.2), all 8 cores were properly utilized.

Here is some of the output from my current message log:

28/08/2007 4:36:50 PM||Starting BOINC client version 5.10.20 for windows_x86_64
28/08/2007 4:36:50 PM||log flags: task, file_xfer, sched_ops
28/08/2007 4:36:50 PM||Libraries: libcurl/7.16.4 OpenSSL/0.9.8e zlib/1.2.3
28/08/2007 4:36:50 PM||Executing as a daemon
28/08/2007 4:36:50 PM||Data directory: C:\Program Files\BOINC
28/08/2007 4:36:50 PM||BOINC is running as a service and as a non-system user.
28/08/2007 4:36:50 PM||No application graphics will be available.
28/08/2007 4:36:50 PM||Processor: 8 GenuineIntel Intel(R) Xeon(R) CPU E5345 @ 2.33GHz [EM64T Family 6 Model 15 Stepping 7]
28/08/2007 4:36:50 PM||Processor features: fpu tsc pae nx sse sse2
28/08/2007 4:36:50 PM||OS: Microsoft Windows Server 2003 "R2": Enterprise x64 Edition, Service Pack 2, (05.02.3790.00)
28/08/2007 4:36:50 PM||Memory: 7.99 GB physical, 19.54 GB virtual
28/08/2007 4:36:50 PM||Disk: 29.56 GB total, 19.88 GB free
28/08/2007 4:36:50 PM||Local time is UTC -7 hours

28/08/2007 4:36:50 PM||Preferences limit memory usage when active to 4092.87MB
28/08/2007 4:36:50 PM||Preferences limit memory usage when idle to 7367.16MB
28/08/2007 4:36:50 PM||Preferences limit disk usage to 19.41GB
28/08/2007 4:36:50 PM||Running CPU benchmarks
28/08/2007 4:37:24 PM||Benchmark results:
28/08/2007 4:37:24 PM|| Number of CPUs: 4
28/08/2007 4:37:24 PM|| 2216 floating point MIPS (Whetstone) per CPU
28/08/2007 4:37:24 PM|| 6713 integer MIPS (Dhrystone) per CPU

In your preferences, how many CPUs do you say that BOINC can use?
Preferences not only on the website, but also in the Simple/Advanced preferences options.

---

I have it left it at its default setting of 16.

Sometimes, youll have to change the windows boot.ini, or update the HAL. For the HAL, just updating or reinstalling it will correct this. However, if it doesnt, youll have to update the boot.ini in windows from /numproc=*whatever* to /numproc=*the right amount*.