Zenmastur wrote: ↑Mon Aug 03, 2020 6:09 am
Joost Buijs wrote: ↑Sat Aug 01, 2020 5:00 pm
...
Memory speed is not very important, the difference in speed I measured between 2133 MT/s and 3200 MT/s memory is at max. 5%, buying very expensive G.Skill memory with low latency to gain maybe 1 or 2% is IMHO complete nonsense.
I see statements like this a lot.
The first thing to note is the performance of the memory subsystem is, to a great extent, determined by the BIOS. Jedec/XMP profiles only store a few of the memory timings needed to initialize the memory subsystem. The rest are determined at boot time by a process called “learning” in which the BIOS tries different values in the many timing parameters visible in most BIOSs. Not all parameters are visible in the BIOS and therefore can't be changed or modified by “normal” means.
The other MAJOR issue is the quality of the MB memory trace layout. A poor design, will perform poorly and may not allow the RAM to reach it's full potential.
Since there are several different RAM manufacturers, many different memory chips with different strengths and weaknesses, many different retail memory vendors, many different motherboards manufactures, and many different BIOSs out there making a claim like “Memory speed is not very important,” is completely worthless and misleading.
If you know relatively little and just buy a bunch of “RANDOM” parts and then do NOTHING other than enable your XMP profile you can expect shit result most of the time. If you want better results, you have to put a little more time and effort in to choosing your motherboard and RAM. During setup you have to take the time to control most or ALL of the memory timings.
Most people aren't willing to do this because it takes time and can be frustrating if you don't have a clue what's going on.
On my system the difference between running the ram at 2133 and 3200Mhz was about 12% in NPS using stockfish. That was just for enabling the XMP profile. I got another 3-4% by tweaking the ram parameters even though I have crap ram sticks (crap meaning they don't overclock well). They're stable enough, just not much head room for overclocking. E.g. I couldn't get them stable at any speed faster than 3200Mhz but some of the timings at 3200 could be cut to fraction of the value the BIOS had them set at. Many of the parameters weren't even close to the minimum at which they would run stable.
Different BIOSs will perform the “learning” tasks with different results. Some are good at it and some aren't. Certain types of chips will perform better than others, not because they are “better” in general, but because the BIOS finds better parameters for those chips. The easiest way to get around this is to manually control ALL the available timing parameters. Like this:
Code: Select all
Memory Type= Hynix CJR 128GB 8 X 8Gb Dual Rank DDR4-2133 C/18nm lithogrophy Downbin MB=B0 Rev. 8-layer Page 1Kb 8 Dimms Gear-down mode Disabled
DDR4-2133 Time ns DDR4-3200 Time ns DDR4-3200 Time ns DDR4-3200 Time ns
Parameter Description Parameter JDEC@1067 XMP@1600 Actual (tested) BIOS set@1600
CAS latency tCL 15 14.1 16 10.0 14 8.8 16 10.0
RAS to CAS Delay read tRCDRD 15 14.1 18 11.3 15 9.4 18 11.3
RAS to CAS Delay write tRCDWR 15 14.1 18 11.3 17 10.6 18 11.3
RAS Precharge time tRP 15 14.1 18 11.3 17 10.6 19 11.9
Active to Precharge Delay Time tRAS 36 33.7 36 22.5 28 17.5 36 22.5
Act to Act/Refresh Delay Time tRC 50 46.9 54 33.8 42 26.3 56 35.0
Short Row Active to Row Active Delay tRRDS 4 3.7 6 3.8 4 2.5 6 3.8
Long Row Active to Row Active Delay tRRDL 6 5.6 9 5.6 6 3.8 8 5.0
Long CAS to CAS Delay Time tCCDL 6 5.6 9 5.6 9 5.6 9 5.6
Four Active Windows Delay tFAW 23 21.6 36 22.5 16 10.0 34 21.3
Normal Refresh Recovery Delay Time tRFC1 312 195.0 560 350.0
2x mode Refresh Recovery Delay Time tRFC2 192 120.0 440 275.0
4x mode Refresh Recovery Delay Time tRFC4 132 82.5 255 159.4
Write to Read delay Short tWTRS 3 1.9 4 2.5
Write to Read delay Long tWTRL 9 5.6 12 7.5
Write recovery time (8 CLK min.) tWR 12 7.5 12 7.5
Read to Read delay same bank group tRDRD SCL 3 1.9 4 2.5
Write to Write delay same bank group tWRWR SCL 3 1.9 4 2.5
CAS Write Latency tCWL 14 8.8 16 10.0
Read to Pre-charge Time tRTP 8 5.0 8 5.0
Read Write Command spacing tRDWR 5 3.1 7 4.4
Write Read Command Spacing tWRRD 1 0.6 3 1.9
Write to Write Time same chip tWRWR SC 1 0.6 1 0.6
Write to Write Time same DIMM tWRWR SD 3 1.9 7 4.4
Write to Write Time diff. DIMM tWRWR DD 3 1.9 7 4.4
Read to Read time same chip tRDRD SC 1 0.6 1 0.6
Read to Read time same DIMM tRDRD SD 3 1.9 5 3.1
Read to Read time diff. DIMM tRDRD DD 3 1.9 5 3.1
Clock enable time tCKE 1 0.6 1 0.6
The first four columns show what the JEDEC/XMP profiles control and the latencies at the given clock speed. The second four columns show what I manually set them to and what the BIOS set them to along with latencies. In some cases the difference between what the BIOS set them at and what they will reliably run at is VASTLY different. Two likely causes are the Hynix CJR chips were relatively new and the bios is probably tuned for Samsung and Crucial chips or earlier Hynix chips.
Some of the "Tested" timing are VERY pedestrian while others are VERY fast compared to other types/brands of memory chips. I got about an extra FEW IN PERFORMANCE OVER AND ABOVE THE PERFORMANCE THE XMP PROFILE PROVIDED. THE REASON THIS IS SO LOW IS BECAUSE THESE CHIPS WON'T RUN RELIABLY FASTER THAN 3200MHZ EVEN WITH HIGH VOLTAGES. But at the time I bought them I didn't really have another choice and I was tired of waiting for better memory to become available. Samsung B-die chips are known to run very fast. A lot faster than the ones I bought.
On Ryzen chips faster memory means faster infinity clocks (up to the fabrics clock limits) which means lower memory latency. Most AB engine are latency sensitive ( not sure about NN and NNUE) so lower latency means more NPS.
So, picking random components and expecting stellar performance isn't likely to happen. But people expect it to perform better because they spent more money on the RAM. Few ever think about learning what makes a memory subsystem fast. They just spend money and hope that's good enough. This happens all the time and then you see claims that faster memory doesn't make a difference.
If you want stellar memory performance you need to know a lot and specify every component, even the BIOS revision your going to use and then spend the time to actually set the parameters and do the testing to VERIFY that the settings you choose are actually faster. If you're not going to do that then it “IS” a waste of money.
Last note: The memory times given in this post aren't likely to run on any other system unless they have the exact same components as I do, and even then they will likely need to be tweaked to match your CPU/MB/Memory Dimms due to silicon lottery effects.
Regards,
Zenmastur