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Are there any tools to determine current memory clock speeds on Linux systems? (Specifically Debian 10.)

From my searching so far I am aware of dmidecode, but this does not report true current frequency settings. (It appears to report default DDR speeds. On one system I have it reports "Unknown", and on the other 800MT/s, which I don't know how to interpret, and it certainly isn't the current speed.)

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  • Are you sure 800MT/s isn’t the current speed? That matches DDR2-800 or DDR3-800, and corresponds to 6.4GiB/s (see the data width shown by dmidecode). The dmidecode information on the systems I have at hand is accurate. – Stephen Kitt Sep 22 '20 at 11:40
  • Is there a way to convert 800MT/s to clock speed? – user3728501 Sep 22 '20 at 11:42
  • Assuming DDR, the clock speed is half the transfer rate. – Stephen Kitt Sep 22 '20 at 11:44
  • So the clock speed is 400 MHz? That is clearly wrong. – user3728501 Sep 22 '20 at 12:05
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    The lack of output from modprobe means it worked ;-). The information is supposed to be accurate regarding the DIMM capabilities, it’s read from the SPD EEPROMs on the DIMMs; but the bank (the physical location of the DIMM) is just a guess. The output suggests you weren’t sold what you thought you were buying... What does your firmware setup say about your memory configuration? – Stephen Kitt Sep 22 '20 at 16:39
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Both dmidecode and lshw report the correct memory speed here:

sudo dmidecode --type 17 | grep Speed | head -1
Speed: 3600 MT/s

I'm running dmidecode-3.2-5.fc32.x86_64

lshw is also correct:

sudo lshw -short -C memory
16GiB DIMM DDR4 Synchronous Unbuffered (Unregistered) 3600 MHz (0.3 ns)
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  • DDR memory speed has always been reported in MT per second, so there's no error. RAM vendors have long adopted MHz instead of MT because it's simpler for the customer. See: en.wikipedia.org/wiki/DDR4_SDRAM#Modules – Artem S. Tashkinov Sep 22 '20 at 12:41
  • Everything is correct. Open NewEgg and Amazon and find me a single RAM module for which the physical refresh rate is specified. You'll find none. – Artem S. Tashkinov Sep 22 '20 at 12:43
  • I’m not going to read through every single RAM module description on NewEgg and Amazon, I’m going by the specs (see also the Wikipedia link you gave above). So I take it these are “marketing MHz”, not real MHz :-(. – Stephen Kitt Sep 22 '20 at 12:52
  • So I take it these are “marketing MHz”, not real MHz :-(. Been like that since DDR1 days - I wonder why it's taken you more than a dozen years to notice that :-) Yes, they are "marketing" MHz. :-) – Artem S. Tashkinov Sep 22 '20 at 16:38
  • The RAM manufacturer I have been buying from for over 20 years only quotes MT/s for DDR, with no unit (“DDR4-3200” etc., as per JEDEC), so I didn’t pay much attention to “MHz” values elsewhere. – Stephen Kitt Sep 22 '20 at 16:46

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