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JimmyH
08-10-2016, 08:50 PM
What does it mean when it says 'When the M2 is operating in SATA mode, SATA Express 1 will only support PCIE modem (SATA6G will be disabled).

As I have dual GPU's in SLI, if I were to have a PCIE SSD in the third PCIE slot, is it slower. I don't understand the whole PCIE 3x16, x 8, x 4 thing.

ASUS-OP
08-15-2016, 01:28 AM
Hi JimmyH,

The Maximus VIII Formula utilizes the Intel Flexible I/O architecture, allowing resources to be shared on your board to enrich and maximize its expansion.
In your case, the first two PCIe slots are shared, while sharing direct resources coming from the CPU.
You can have the first slot at x16 when there is nothing on the second slot, or have them both occupied, and have them ran at x8 lane bandwidth each to share the x16 lanes of resources available.

The 3rd PCIe slot comes from the PCH (the Z170 chipset), which is interlinked to the CPU via DMI 3.0 bus at the bandwidth of PCIEe 3.0 x4 lanes max. This means devices installed on this slot will share bandwidth with all SATA, USB, and PCIe devices on the board (include the network card).
As the bandwidth of this slot shares with SATA5_6 port (mutual exclusive), if you want to use these two SATA slots, your PCIE SSD will perform at half the performance.

PCIe revision all has different bandwidth per each lanes. For instance:

- PCIe 1.0 has 2.5GT/s per a lane. So for x4 lane of PCIe 1.0 will give you roughly 1GB/s throughput at max. (This is theoretical value, actual value should be roughly 80% of it due to latency and other variables.)
- PCIe 2.0 has 5.0GT/s per a lane. So for x4 lanes of PCIe 2.0 will give you roughly 2GB/s throughput at max. (This is theoretical value, actual value should be roughly 80% of it due to latency and other variables.)
- PCIE 3.0 has 8.0GT/s per a lane. So for x4 lanes of PCIe 2.0 will give you roughly 3.2GB/s throughput at max. (This is theoretical value, actual value should be roughly 80% of it due to latency and other variables.)