Memory frequency information

[YuryG]

Hello, can I find actual memory frequency information on running FreeBSD with some command? Something like CPU-Z on Windows.
I have an AMD chipset oldish motherboard with FX-8300 CPU. And CPU frequency is visible via dev.cpu sysctl, but how about RAM?

 

[cracauer@]

dmidecode

 

[YuryG]

dmidecode

Thanks.

Then I have the next question. Somehow on Windows on this machine CPU-Z shows 800MHz (as it should since PC3-12800 is inserted and without any overclocking), but in dmidecode on FreeBSD I see 667MHz. Why this could be? ?
May be some memory benchmark measuring could help get the real speed?

 

[skunk]

Maybe you have two banks of memory and thus the clocking of the UDIMMs has been reduced to compensate for the extra bus load?
Maybe CPU-Z just reads the SPD data (dmidecode field "Speed"), but does not show the actual bus speed (dmidecode field "Configured Memory Speed")?
Anyway I am wondering also... this computer here has PC3-14900R and both banks are filled. Thus afaiu the bus speed should be reduced from 1866 to 1600. But "Configured Memory Speed" still shows 1866... *confused*

Edit: With AMD AM-2/3 and UDIMMs I recall something like 1 module: 1300MHz, 2 modules 1066, 3 modules 800, 4 modules 667MHz. Maybe this is what you are seeing?

 

[cracauer@]

No, using 2 modules in a dual-channel configuration should not lower the frequency. Only using multiple UDIMMs per channel should.

The BIOS might have an additional display of memory speed.

 

[YuryG]

It looks like the opposite: CPU-Z shows real-time data, since it is 803-804MHz (dual-channel mode) and a bit changing. The BIOS on this motherboard shows actual "auto" timings 11-11-xx which correspond to 1600MHz frequency, although do not show the frequency itself.

 

[SirDice]

The BIOS on this motherboard shows actual "auto" timings 11-11-xx which correspond to 1600MHz frequency

RAS and CAS wait states have very little to do with the frequency. You can get DIMMs with the same frequency but have different wait states.

 

[YuryG]

RAS and CAS wait states have very little to do with the frequency. You can get DIMMs with the same frequency but have different wait states.

I understand that. But for my DIMMs written parameters are 11-11-11-30 for 1600MHz and 9-9-9-24 for 1333MHz. Usually they are linked and I haven't modified them in BIOS settings.

By the way,

<...>
Maybe CPU-Z just reads the SPD data (dmidecode field "Speed"), but does not show the actual bus speed (dmidecode field "Configured Memory Speed")?
<...>

I do not see "Configured Memory Speed" in a dmidecode output at all, only "Speed" field.
So, I believe it is a lack of information on FreeBSD that is available for CPU-Z on Windows. Or could it be Windows-specific OS-level memory speed regulation? For example, I couldn't find a way to see (use?) Turbo boost mode for a core on FreeBSD, that is visible on Windows, may be the similar is for memory modes.

(And I understand that real performance difference from 1333MHz to 1600MHz memory modes is almost negligible, just like very restricted use of CPU's core Turbo mode.)

 

[cracauer@]

At this point I would go into the BIOS and reduce the memory multiplier by 1/3 or 1/2, and then consult CPU-z and dmidecode again to see who picked up the change.

 

[skunk]

I do not see "Configured Memory Speed" in a dmidecode output at all, only "Speed" field.
So, I believe it is a lack of information on FreeBSD that is available for CPU-Z on Windows.

My personal guess is that this is caused by incomplete DMI data, a common deficiency with consumer boards, and CPU-Z probably using other methods to determine/guess the actual values.

I just turned on a Supermicro experimentation computer with RDIMMs. It also shows "Configured Memory Speed", consistent with the value shown in the BIOS.
In the storage room I have two UDIMM-equipped computers, one with an AM-3 consumer board. I am already curious whether they'll contain the "Configured Memory Speed" in their DMI data block. Will report back when I look at them.