[QUOTE=kladner;451113]I exchanged the XMP 2400 parts for XMP 3000. Strangely, running a single, four thread worker is slightly (0.10 to 0.20 ms) slower, now. Would the increased speed show up if I were running more than one worker?[/QUOTE]
One worker wouldn't max the memory bandwidth

[QUOTE=henryzz;451114]One worker wouldn't max the memory bandwidth[/QUOTE]
Thanks! I'll move toward multiple workers.

[QUOTE=henryzz;451114]One worker wouldn't max the memory bandwidth[/QUOTE]

One worker with four threads would max the memory bandwidth.

It's kind of obvious, but have you confirmed the XMP profile is enabled and working?

[QUOTE=Mark Rose;451125]It's kind of obvious, but have you confirmed the XMP profile is enabled and working?[/QUOTE]
'Fraid so.
EDIT: On the bright side, the parts trade only set me back 45 minutes, and $3.45 price difference.

One factor which might be in play here is that the original XMP-2400 RAM was CAS 14, while the XMP-3000 is CAS 15. The difference in ms/it is 2.628 versus ~2.877.

[QUOTE=kladner;451217]One factor which might be in play here is that the original XMP-2400 RAM was CAS 14, while the XMP-3000 is CAS 15. The difference in ms/it is 2.628 versus ~2.877.[/QUOTE]

14/(2400/2) MHz = 11.7 nanosecond latency
15/(3000/2) MHz = 10.0 nanosecond latency

Try running the new RAM at 2400 & 14? The slowness may be the single/dual rank thing mackerel stumbled upon.

[QUOTE=Mark Rose;451222]14/(2400/2) MHz = 11.7 nanosecond latency
15/(3000/2) MHz = 10.0 nanosecond latency

Try running the new RAM at 2400 & 14? The slowness may be [U][B]the single/dual rank thing[/B][/U] mackerel stumbled upon.[/QUOTE]
That seems a possibility. Another is that the earlier run at DDR4-2400 may also have had the CPU cores locked into Turbo at 4200 MHz. Switching to XMP does that, and I did not include CPUZ in that screen grab to show the core clocks.

I wish I had paid more attention when I had the previous set so I could give a positive answer. It is a relatively small difference in any case: 0.1 to 0.15 ms/it, more or less.

To update: With regard to the relative speed of different memory modules, I have come to the conclusion that there are too many variables at play to clearly assign causes for the numbers that turn up in a particular LLDC run. The earlier "slower" RAM had the advantage of fewer cycle hogging apps, especially performance monitoring apps. Earlier in the rebuild, things were more basic.

I can see tenths of milliseconds difference per iteration by shutting down and restarting things like HWiNFO64. Worse yet are things like Corsair Link. Worst of all, so far, is Asus AI Suite III. Even if the main program is shut down, there are 3-4 services which keep running. These can be disabled, but not stopped without a reboot.

The current RAM, rated XMP 3000, seems to be happy at 3200 with timings relaxed a bit. I am seeing the kind of 2.6x ms/it that I screen grabbed at least once from the "old" RAM. especially if I shut down the cycle hogs. The other biggie in this category is [STRIKE]a browser[/STRIKE] Firefox with multiple tabs and windows open.

I now close everything I can if the system is going to run otherwise unused for some hours (like work or sleep.)

Well, I have the opportunity to exchange RAM again. One of the current modules has gone flaky on me. It throws about 500 errors in the first second of Memtest86 v7.2.

Now I have been digging through web sites trying to find dual rank information. Crucial gives the info for some product lines, but not others. As near as I can tell, in the following part numbers, the "D" preceding the last numeric string signifies Dual.
CT2K8G4DF[U][B]D[/B][/U]824A ** Crucial
CT2K16G4DF[B][U]D[/U][/B]8213 ** Crucial
CT2K16G4DF[U][B]D[/B][/U]824A ** Crucial

On the other hand, CT2K8G4DF[B][U]S[/U][/B]8213 is listed as Single. There are other numbers with a "D" in that position which do not list Rank.

I have a question out to Corsair regarding Dual rank modules.

[QUOTE=kladner;453149]Well, I have the opportunity to exchange RAM again. One of the current modules has gone flaky on me. It throws about 500 errors in the first second of Memtest86 v7.2.[/QUOTE]

Please forgive me for this, but have you run further experiments?

For example, are you absolutely _sure_ that that one module is at fault? Perhaps it's the motherboard or the controller. Or, perhaps, it simply isn't seated properly. Have you tried switching them around and see what happens?

My apologies if I am telling you how to chew gum. But I have found that crying wolf is not wise if a wolf is not present.