[SOLVED] Need help with very normal frequency number but low read and write speed

[fresh.sock8544]

Hi, I'm experiencing a weird problem with my home server.

Spec:
EPYC 7542*2, Dell R7525
2*3200MT DDR4 ECC(single channel)
Latest BIOS from Dell. Default BIOS settings, but NPS changed to 4.

Everything related to CPU(all core 3.2GHz) and RAM frequency(3200Mhz in task manager, 1590Mhz in CPU-Z(but its DDR, so is this normal?)) numbers are perfect, but the RAM read speed from AIDA64 RAM benchmark is showing only ~5GB/s. I think it should be about 30GB/s. This causes my system performance to be 1/5 than its original.

Passed memtest+
Tested from different OS but the results are the same.

There is no error message either in Windows event viewer, or dell's iDRAC diagnose (base on that, dell's customer service told me that there is no problem with the hardware and refused for a replacement).
Because the parts are expensive and not compatible with normal PC, I think I can't use the swapping-part method to diagnose.

So... Do you think it is a memory problem or CPU problem or something else. Do you have suggestions to find out?

 

[Aeacus]

AM frequency(3200Mhz in task manager, 1590Mhz in CPU-Z(but its DDR, so is this normal?))

CPU-Z shows RAM frequency in Single Data Rate (SDR). But since RAM is Double Data Rate (DDR), multiply it by 2 to get exact value. 1590 x 2 = 3180 ~ 3200.

RAM read speed from AIDA64 RAM benchmark is showing only ~5GB/s. I think it should be about 30GB/s.

Why do you think RAM read speed should be 30 GB/s? 🤔

2*3200MT DDR4 ECC(single channel)

2 sticks for that dual-CPU rack server is not enough. Bare minimum would be 4 sticks, so that you can run your RAM in dual-channel. Heck, you can even upgrade RAM to 8 channels, which is insane. Especially since consumer PCs have max 2 channels (or 4 channels, when using Threadripper/Xeon CPU).

Here's performance comparison between single- and dual-channel,
link: https://ram.userbenchmark.com/Compa...vs-HyperX-Fury-DDR4-2133-C14-2x4GB/3555vs3554

While the comparison uses consumer grade RAM, same performance difference (or even higher) applies to server grade RAM as well.

So, get at least 2 sticks of RAM more, and install them in dual-channel.
Here's the RAM channel layout in your rack server,
link: https://www.dell.com/support/manual...65c17a-2613-45b2-9204-c02a89225024&lang=en-us

 

[Karadjgne]

There's always a loss. BCLK is supposed to be 100.0 but hardly ever actually is, it generly runs 99.8± and that's reflected in ram speeds, so your 3200MHz will run 3180MHz instead. If you want it to run the full rated 3200MHz, bump BCLK to 100.1 or 100.2 on bios, and cpu-z will move from 99.8 to 100.0.

Theres also a loss because numbers are never fully accurate. The buss used by the ram is based on 266Hz. Which isn't in reality the whole number, it's 266.66...Hz

RRam is buss x multiplier x BCLK, so 3200MHz Ram is physically 3200.04MHz, but since the system is set on 266 numeral not 266.66 actual, by the math 3200MHz ends up as 3192MHz, so it's simply called 3200MHz for convenience and varience, an industry standard rather than a physical reality.

Your ram is running at 3200MHz, there will be some varience and loss, it's normal. Everybody suffers from that, regardless of settings.

According to cpu-z, my 3600 is running at a 100.0 BCLK with a speed of 1799.6 (3599.2)MHz. My old Intel board had a BCLK of 99.8 and the 1866MHz ram ran at 931 (1862) MHz. 100.0 BCLK would have been 1865.7MHz

 

[fresh.sock8544]

Finally, I solved it by unplugging and re-plugging the power cable after 10 minutes(a normal OS reboot doesn't work for me). Also, I noticed that the performance issue started from the last sudden power loss days ago. Not sure what reason caused this problem.

CPU-Z shows RAM frequency in Single Data Rate (SDR). But since RAM is Double Data Rate (DDR), multiply it by 2 to get exact value. 1590 x 2 = 3180 ~ 3200.

Thank you for your explanation

Why do you think RAM read speed should be 30 GB/s? 🤔

My bad. My point was that it should not be ~5GB/s. Even my SSD outperforms it in terms of speed. Anyway, after I fixed the server's problem, single channel can run at ~18GB/s.

2 sticks for that dual-CPU rack server is not enough. Bare minimum would be 4 sticks, so that you can run your RAM in dual-channel.

Wow, it seems that dual channel doubles the performance. I'll add two more sticks to it.

Your ram is running at 3200MHz, there will be some varience and loss, it's normal. Everybody suffers from that, regardless of settings.

Thank you for your explanation. It is weird because yeah the frequency seems OK, but its real performance(read speed) is very poor. I'm OK with minor performance loss, but I'm talking about 4/5 of performance loss🥹

Anyway, thank you guys again.