You might send this to the Boinc Mailing List as the dual Nvidia gpu's in a single machine problems you are seeing has been a thorn for a LONG time!! For some people at some projects it works just fine, for other people at the same project it does not work at all. You fill up the cache of one gpu and the other gpu sits idle. The ONLY solution so far is too put the two gpu's on different projects, then they both work fine

[buffers]
allow-update-from-altbuffer=no
buffer-file-basename=in
output-file-basename=out
checkpoint-filename=chkpoint

[misc]
run-work-limit=-1

[triggers]
restart-on-config-file-change=no
exit-flag-filename=exit
pause-flag-filename=pause

[display]
progress-indicator=off

[processor-usage]
priority=9

[networking]
disabled=yes

[logging]
log-file-type="no limit"
log-file=stderr.txt

[rc5-72]
random-subspace=1339

use POSIX qw(strftime);

my $path = "C:\\Program Files\\boinc";
my $url =  'http://moowrap.net/'; 
my $task = 'dnetc';
my $limit = 5*60;   # time in seconds (cpu time)

@tasks = `"$path\\boinccmd" --get_results`;
for $i (0..$#tasks) {
  if($tasks[$i]=~/^(\d+)\)/) {
    if($tasks[++$i] =~ /$task/) {
      $tasks[$i] =~ /name: (.*)/;
      $name = $1;
      $tasks[$i + 12] =~ /state: (.*)/;    #check if running
      if($1 == 1) {
        $tasks[$i + 16] =~ /time: (.*)/;   
        $cputime = $1;
        print $name, " ",$cputime;
        if($cputime > $limit) {
          print " (suspending)\n";
          `"$path\\boinccmd" --result $url $name suspend`;
           open(LOG, '>>cpu_watch.log');
           $now = strftime "%Y-%m-%d %H:%M:%S - ", localtime;
           print LOG $now, ' ', $name;
           close(LOG);
        } else {
          print "\n";
        }
      }
    }
  }
}

Thank you all for your suggestions, I will try to do something about this next monday an will let you know the results.

However, with my setup, I don't have cpu utilization problems with 12.1p, but I get errors like this from time to time:

06:11:12 (3760): premature exit detected, app exit status: 0xc0000005

To summarize:
- Catalyst 10.12 - no errors, high cpu usage
- Catalyst 12.1p - random errors (but still getting some credits even if marked invalid), low cpu usage

Thank you all again

06:11:12 (3760): premature exit detected, app exit status: 0xc0000005

06:11:12 (3760): input buffer 10 packets (1792 bytes), checkpoint file 2 packets (384 bytes), output buffer 0 packets (0 bytes)
06:11:12 (3760): premature exit detected, app exit status: 0xc0000005
06:11:12 (3760): wrapper: running dnetc518-win32-x86-stream.exe (-ini dnetc.ini -runoffline -multiok=1) - attempt 2/10