SCommDll fails with strange status on multi core CPUs

FAQ #100674

 

Symptom
On a PC equipped with e.g. an AMD Athlon 64 X2 processor it is possible that the SComm driver fails with strange status messages. We have observed this problem on AMD Athlon 64 X2 processors produced in 2006 but the problem can potentially happen on all multi-core processors.

Reason
There is a serious problem with some series of AMD Athlon 64 X2 processors. The timing functions in the BIOS have a bug and can cause the SComm fail with strange status. The problem seems to be related to the variable clock rate feature of the CPU.

Solution
Microsoft and AMD had to fix this problem. Please refer to the links attached to this FAQ and apply the mentioned update on your system if necessary.

How to detect if your CPU is affected?
There is a simple test program that allows to detect if a CPU is affected. Procede as follows:
- store the attached dll vb6fr.dll in your /windows/system32 folder unless it is already present there
- run the attached projet.exe and go to the second screen. If everything is OK the fourth value in form1 is a rather stable value in the order of 350, if you have a negative or very big value the CPU is affected by the problem