[coreboot] lower memory performance with coreboot on KGPE-D16
Daniel Kulesz
daniel.ina1 at googlemail.com
Fri Oct 5 21:58:04 CEST 2018
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
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