Over-reporting miner?

Question

I'm running the puddinpop rpcminer-opencl.exe that came with Guiminer. I'm running it with crazy settings -gpugrid=128 -gputhreads=256 -aggression=14 on a FirePro 2270 workstation card, and it's reporting about 20 GH/s which I understand is not even remotely possible. I assume something went wrong and all my hashes are broken somehow, but how do I troubleshoot this?

Update: The same miner works fine on one of my other machines. I did find this output on the console:

Build program rval=0
build STATUS:
build LOG:C:\Users\Sean\AppData\Local\Temp\OCLF1AC.tmp.cl(51): warning: attribute "vec_type_hint" ignored
__kernel __attribute__((vec_type_hint(uint))) WORKGROUP void opencl_process(__global opencl_in *in, __global opencl_out *out, const uint loops, const uint bits)
^
Create kernel rval=0
Done allocating OpenCL resources for (128,256)
Finding best configuration step end (128,256) 6ms  prev best=9223372036854775807ms
Done allocating OpenCL resources for (16,16)

So the warning is odd, but also that last extra (16,16) line doesn't show up on my other machine that works.

Update 2: With "crazy" settings I get no shares. If I run with no options, it reports 10 MH/s and seems to get about one share every 10 minutes. So somehow changing the settings makes it generate no shares at all!

Answer 1

I agree, that 15W card should calculate hashes slower than anything listed at https://en.bitcoin.it/wiki/Mining_hardware_comparison - 20MH/s sounds about right. You probably misread the units (1GH = 1000MH), or the software has a bug and miswrote them.

Answer 2

From memory, when pool mining I can solve about 220 shares per hour with 270MH/s. You could work out an approximate hash rate based on the number of shares solved.