According to Multi-channel memory architecture - Wikipedia you should prefer a "matched pair".
Otherwise check out: Frequently Asked Questions for Intel® Graphics Memory on Windows® 10
There is an urgent BIOS update available for your rig:
Thanks. I have already updated my BIOS. I have heard that 8GB + 16GB memory can make up the "Intel Flex Memory Technology", where 8+8 dual channel and 8 single. I just want more RAM, 32GB is best surely, but now the memory price.....emmmm u know. So 24 GB may be better to me if the bandwidth benefit to graphics works.
Honestly i wasn't aware of Intel Flex.
Anyway here is the official documentation, page 23f:
System Memory Organization Modes
The IMC supports two memory organization modes, single-channel and dual-channel.
Depending upon how the DDR Schema and DIMM Modules are populated in each
memory channel, a number of different configurations can exist.
In this mode, all memory cycles are directed to a single channel. Single-Channel mode
is used when either the Channel A or Channel B DIMM connectors are populated in any
order, but not both.
Dual-Channel Mode—Intel® Flex Memory Technology Mode
The IMC supports Intel Flex Memory Technology Mode. 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.
Channels A and B can be mapped for physical channel 0 and 1 respectively or vice
versa; however, channel A size must be greater or equal to channel B size.
Dual-Channel Symmetric Mode (Interleaved Mode)
Dual-Channel Symmetric mode, also known as interleaved mode, provides maximum
performance on real world applications. Addresses are ping-ponged between the
channels after each cache line (64-byte boundary). If there are two requests, and the
second request is to an address on the opposite channel from the first, that request can
be sent before data from the first request has returned. If two consecutive cache lines
are requested, both may be retrieved simultaneously, since they are ensured to be on
opposite channels. Use Dual-Channel Symmetric mode when both Channel A and
Channel B DIMM connectors are populated in any order, with the total amount of
memory in each channel being the same.
When both channels are populated with the same memory capacity and the boundary
between the dual channel zone and the single channel zone is the top of memory, IMC
operates completely in Dual-Channel Symmetric mode.
Note: The DRAM device technology and width may vary from one channel to the other.