Hi Iru,
I just found the memory performance on KGPE-D16 is lower when running with coreboot. I have two Opteron 6276 and 8 16GB DDR3-1600 RDIMM on all orange slots. I tested it with `hdparm -tT /dev/sda` and see the `Timing cached reads` result. With coreboot, this value is around 3000 MB/s, but with OEM firmware it can go to around 3600 MB/s. I think the disk cached read speed is related to memory performance.
Are you using DDR3L-RDIMMs? And did you check whether your memory really runs at 800 MHz? My experience is that coreboot sets the clock down to 667 MHz when running on 1.35V (low voltage), while the vendor bios seems to run modules at 800 MHz in low voltage mode, resulting in higher performance. According to Timothy, this is "over the spec" and thus not set in coreboot by default (you can choose between 1.5V 800 MHz or 1.35V at 667 MHz - but may depend on the used modules).
You can check e.g. in dmidecode. Below is an example (serial number x'd out):
Handle 0x000E, DMI type 17, 40 bytes Memory Device Array Handle: 0x0006 Error Information Handle: Not Provided Total Width: 72 bits Data Width: 64 bits Size: 8192 MB Form Factor: DIMM Set: None Locator: NODE 0 DIMM_D2 Bank Locator: Not Specified Type: DDR3 Type Detail: Synchronous Registered (Buffered) Speed: 800 MHz Manufacturer: Samsung Serial Number: xxxxxxxxx Asset Tag: Not Specified Part Number: M393B1K70DH0-YK0 Rank: 2 Configured Clock Speed: 800 MHz Minimum Voltage: 1.35 V Maximum Voltage: 1.5 V Configured Voltage: 1.5 V
Btw.: I am getting around 3700 MB/sec with hdparm -Tt on my /dev/sda (mechanical disk) and around 3840 MB/sec on /dev/nvme0n1 (PCIe M.2 SSD).
Cheers, Daniel