[mythtv-users] Optimal RAM Allocation for Intel

[Jim C]

>> But when using onboard decoding and OpenGL painter, it's actually
>> probably about the minimum you can get away with for MythTV.  256MB
>> might work, but don't be surprised if it doesn't--or, more
>> confusingly, if it doesn't *always* work (meaning it may work when
>> you test things out, but after some time or for some shows or ...,
>> you get failures that you may no longer think are related to the
>> available graphics memory since it seemed like everything was fine
>> before).
> I think it just dawned to me why my wife's desktop couldn't run the
> frontend ...
>
> Thanks!
>
Info on the net from Intel indicates that their modern GPU 
implementation like the HD 4600 is not dependent on reserved RAM (beyond 
what small amount is needed at boot), and that the DVMT is more 
important. The RAM for the GPU is dynamically allocated, based on need, 
up to the limit set in the BIOS for DVMT. Provided there is sufficient 
RAM to avoid contention when the dynamic allocation is needed the GPU 
will get what it needs. In my case, if the DVMT limit is set to 
"Maximum" the GPU could use up to 2GB of the 4GB available in my system. 
I don't expect Mythtv's video requirements to ever reach the 2GB level, 
so I've set the DVMT limit to Maximum to allow for best flexibility. The 
next step down from Maximum was 250MB, and that seemed a little low.

The data also discussed the benefits of the Intel Unified Memory 
Architecture wherein the GPU has the same fast memory access bandwidth 
as the CPU, reportedly 25GB/s for the HD 4600.

Don't know if this is helpful to others - just passing it along for 
consideration. Certainly, other CPU/GPU combinations could have 
different specifics.