Mixing memory in Acer Aspire laptop

EClyde

TS Evangelist
1 4gb samsung pc3-12800 1.35 v
1 4gb nanya pc3-10600 1.5 v

The timings are listed different on the stick.
HWInfo reports that at 666.7 both are 9-9-9-24
Crucial will sell me all 1.35 v memory as upgrades and the 4830T-6678 Timeline X came with the nanya@1.5v
The laptop boots and runs with both sticks installed

Any thoughts on this?

Thanks