Epyc NVME 7443P

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lihp

Active Member
Jan 2, 2021
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AMD EPYC 7443P working...
I tested this theory, and it doesn't work with 8-channel EPYC CPUs.
Sorry, I disagree.
1628725870297.png

Explanation:
dmidecode -t memory | grep "Bank Locator:"
There you see all eight memory channels populated.

dmidecode -t memory | grep "Module"
Product ID: unknown is the second memory channel of each module. No module installed are the empty banks.

------------------------------

Maybe you just picked the wrong modules?
 
Last edited:

lihp

Active Member
Jan 2, 2021
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Have you had a chance to test actual memory bandwidth?
You can actually check my memory yourself. Second post in this thread at the signature of the post leads directly to a passmark test - click on memory mark and you get:


- Memory Mark Memory Test Info3,301
full star
full star
full star
full star
empty star
Database Operations18,802 KOps/Sec
Memory Read Cached30,315 MBytes/Sec
Memory Read Uncached22,801 MBytes/Sec
Memory Write20,107 MBytes/Sec
Available RAM231,236 Megabytes
Memory Latency56 ns (lower is better)
Memory Threaded98,537 MBytes/Sec

30-32 GB/s looks fine with me?

PS - EDIT: 98,537 threaded isn't great, but isn't shabby either...
 

ectoplasmosis

Active Member
Jul 28, 2021
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30-32 GB/s looks fine with me?

PS - EDIT: 98,537 threaded isn't great, but isn't shabby either...
Theoretical 8-channel bandwidth at 3200 speeds is over 200GB/s. Your threaded result is consistent with quad-channel, and my results running 4x dual-rank DIMMS.

You’ll double your effective bandwidth by filling all 8 slots and activating 8-channel interleaving.
 

alex_stief

Well-Known Member
May 31, 2016
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You really don't get 8 channels worth of bandwidth, just because you used 4 DIMMs with 2 or 4 ranks. That's not how any of this works.
It is slightly better than one rank per channel, but nowhere near 8 channels populated with a DIMM.
 

lihp

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Jan 2, 2021
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Figure I check speed on next boot first and see from there. Ill keep the results posted.

And yes, not a memory geek, but still surprised.
 

ectoplasmosis

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Jul 28, 2021
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Figure I check speed on next boot first and see from there. Ill keep the results posted.

And yes, not a memory geek, but still surprised.
From my understanding, a dual-rank DIMM is akin to having two DIMMs connected to a single channel.

For example, if your EPYC motherboard were to have 16 slots, it would be functionally the same whether you populated 16 slots with single-rank modules or 8 slots with dual-rank.

In your case, you'll need all 8 slots populated in order to achieve 8-channel bandwidth, and feed that thirsty RAIDIX NVMe array.
 

alex_stief

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May 31, 2016
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Worth a read in my opinion.
 
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lihp

Active Member
Jan 2, 2021
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In your case, you'll need all 8 slots populated in order to achieve 8-channel bandwidth, and feed that thirsty RAIDIX NVMe array.
You are correct. Thanks for pointing it out.

So lets see when I am going for that another 256GB RAM... ;)