Intel integrated Graphics performance in flex asymmetric Dual channel

[7MikeG]

Hi All

 

I am trying to find any information regarding the operation of Intel integrated Graphics operating in Flex Memory mode. there are obvious proofs and substantial evidence that having dual channel memory operation increased the performance of an iGPU as the memory interface to the iGPU is now 128 bit, rather than 64 bit in single channel.

 

With the advent of DDR2 can Intel Flex Memory operation, which is as follows (from the Intel processor specs): "Memory is divided into a symmetric and asymmetric zone. The symmetric zone starts at the lowest address in each channel and is contiguous until the asymmetric zone begins or until the top address of the channel with the smaller capacity is reached. In this mode, the system runs with one zone of dual-channel mode and one zone of single-channel mode, simultaneously, across the whole memory array.

 

Since many modern laptops come with a fixed amount of soldered ram on the motherboard, say 4 gb adding a soDIMM of RAM is not only highly necessary (as 4 is too little for any sort of medium use in say chrome and Win 10), but will also result in gains in iGPU performance of 10-25% depending on application, as it now has a full dual channel 128 bit memory interface instead of the 64 bit that it had with just the single channel soldered on board memory. 

 

However with modern apps and programs (Chrome, Windows, Photoshop etc.) needing so much RAM, it would make sense to just up the capacity of the new soDIMM to say 8 gb, resulting in a system wide capacity of 12 gb. Now according to Intel, that is divided so that the first 8 gb (soldered + half of the soDIMM) will run in an interleaved dual channel configuration, and the last 4 gb, will be operated in single channel.

 

Which area of the system memory will the iGPU use?

Will it run in single or dual channel bus width?

Will it report transparently to the computer? (ie. report correctly that the iGPU might be running at 64 bit bus width, even though the memory controller tells windows that is in dual channel mode?

 

In otherwords, will upgrading a laptop with 8gb, instead of 4 gb have any effect on the expected gains in graphics power?

The brand of the ram doesn't matter, nor its speed. the question refers to what segment of the memory allocation table the iGPU uses in the Flex memory mode. How does the OS dynamically assign memory to the iGPU, (and which segment will be used). In the dual channel symmetrical mode, the interleaved operation of the ram is simple and alternating. Does running it in Flex mode introduce overhead, that reduced the throughput, or even reduce the bus with (since its impossible to be purely 128 bit bus width.)

 

Kind regards

 

Mike