Discussion:
lower memory performance with coreboot on KGPE-D16
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Iru Cai
2018-10-04 08:23:24 UTC
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Hi,

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.

Iru
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Iru Cai
2018-10-07 07:12:29 UTC
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Hi Daniel,

Thanks for your reply, but it's not the case with me.

I'm not using DDR3L-RDIMMs. My dmidecode output of one DIMM is:

Handle 0x0007, DMI type 17, 40 bytes
Memory Device
Array Handle: 0x0006
Error Information Handle: Not Provided
Total Width: 72 bits
Data Width: 64 bits
Size: 16384 MB
Form Factor: DIMM
Set: None
Locator: NODE 0 DIMM_A2
Bank Locator: Not Specified
Type: DDR3
Type Detail: Synchronous Registered (Buffered)
Speed: 800 MT/s
Manufacturer: Samsung
Serial Number: 7FCC9C13
Asset Tag: Not Specified
Part Number: M393B2G70BH0-CK0
Rank: 2
Configured Memory Speed: 800 MT/s
Minimum Voltage: 1.5 V
Maximum Voltage: 1.5 V
Configured Voltage: 1.5 V

Iru
Hi Iru,
Post by Iru Cai
I just found the memory performance on KGPE-D16 is lower when running
with
Post by Iru Cai
coreboot. I have two Opteron 6276 and 8 16GB DDR3-1600 RDIMM on all
orange
Post by Iru Cai
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
Post by Iru Cai
firmware it can go to around 3600 MB/s. I think the disk cached read
speed
Post by Iru Cai
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
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
--
My website: https://vimacs.lcpu.club

Please do not send me Microsoft Office/Apple iWork documents. Send
OpenDocument instead! http://fsf.org/campaigns/opendocument/
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