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Ram Timing Benchmark (CL/tRCD/tRP/tRAS/CR/tRC/tRFC/tREF)

Jun 9, 2011
32 (0.01/day)
South Korea
Hello. it's newbie on this forum.
I tested my memory with several different ram timing combinations. Tests include:

1. Super PI 32M digits of Pi calculation
2. Lavalys Everest Cache & Memory Benchmark (Bandwidth & Latency)
3. Video Encoding (1080p TP -> mkv with H.264)

Tested ram timing items are:

1. CL: 6~11
2. tRCD: 9~11
3. tRP: 6~11
4. tRAS: 24~30
5. Command Rate: 1 / 2
6. tRC: 15~40
7. tRFC: 90ns / 110ns / 160ns / 300ns / 350ns
8. tREF: 3.9ms / 7.8ms

For test of a ram timing component, other components (except tRC and tREF) are set to the lowest possible values for variable control while tRC and tREF are to have the highest possible values as default.)

System setting is as follows:

- CPU: AMD Phenom II X6 @ 4.0GHz / NB 2.75GHz
- RAM: G.SKILL PIS PC3-19200 CL9 4GB (2GB x 2) @ 2000MHz
- Storage: Intel X25-M G2 80GB
- PSU: PC Power & Cooling Silencer 910W 80PLUS Silver

Before we see the results below, I think I need to mention about the methodology used in this article: I used two different techniques to analyze the results.

First is to analyze 'numerically': calculate the ratio between 'rate of perf. change' and 'rate of ram timing value change'. It emphasizes a ram timing's theoretical contribution to performance, but not necessarily means that we could/would get those amount of perf. gain (or loss) from dealing with said ram timing component since in practice we don't always treat a ram timing as numerical value (e.g. in BIOS, we don't set 10% more to CL, 5% less to tRCD... see what I mean?)

Rather, many BIOSs provide ram timing options as up/down menu so that a user cannot accurately change the value itself but can change only the provided 'degree' (e.g. in many BIOS, for tREF, there's 3.9ms / 7.8ms / 15.6ms... and so on. There's no 4.0ms or 5.0ms. It's likely a 'degree' rather than a 'numerics'.)

So, the second method is to analyze upon 'degree change': calculate the ratio between 'rate of perf. change' and 'number of degrees change'. It is more likely what we can expect when we're dealing with a ram timing component in practice (in BIOS), but it is apart from theory.

Okay. Then we see the results!

1. Super PI

Note that among ram timing items only tRFC and tREF are indexed by 'time unit' (second) while others by clock count (how many clock cycles (= inverse time unit) are consumed for a ram timing's operation). It's because they (tRFC and tREF) directly indicate characteristics of electrical working mechanism of a memory chip. Both are related to a memory's refresh rate: tREF determines how frequently a chip shall be refreshed and tRFC determines the time elapsed between the moment of 'refresh' (memory access is unavailable) and the moment when a memory access is back to available. So in case of tREF, the bigger value implies the better performance.

Theoretical Analysis for Super PI Test

In theory, CL / tRFC / tRCD / tREF and tRAS contribute more than 1% to performance, respectively.
(Note: 4% contribution of CL means, when we change the value of CL by 10%, the performance will be affected by 10% x 4% = 0.4%)

Practical Analysis for Super PI Test

In practice, tRFC and tREF seem to be important since their minimum changeable units of '1-degree' in BIOS are bigger than others. (i.e. CL's minimum unit is '1 clock counts' while tRFC's minimum unit is '20~50ns', which is equivalent to 20~50 clock counts under 1000MHz.)

Jun 9, 2011
32 (0.01/day)
South Korea
3. Everest Cache & Memory Benchmark: Memory Latency

Theoretical Analysis for Latency Test

Practical Analysis for Latency Test

Latency test seems more dependant to ram timings than previous tests (Super PI & Bandwidth).
tRFC / Command Rate and CL affects similarly (around 2~2.5%) in practice.

Jun 9, 2011
32 (0.01/day)
South Korea
4. Video Encoding

This test is to measure the time of converting 1920x1080 TP file to MKV, same resolution.
H.264 codec is used. No GPGPU acceleration.

Theoretical Analysis for Encoding Test

Practical Analysis for Encoding Test

Similar to Super PI test, no ram timing affects more than 1% in practice and tREF is ranked at the highest.

So far, we covered 3 areas: Floating-point calculation, synthetic benchmark and video encoding.
Here's the graphical representation of how a ram timing affects performance through these three areas.

Theoretical Analysis

As you can see, CL holds the most shares in theory. tRFC and tRCD seem meaningful too.

Practical Analysis

In practice, in addition to major shareholders in theory, Command Rate and tREF are also important.

Thanks for reading my article :)

Have a nice day~

PS. this article had also been uploaded to my blog: http://udteam.tistory.com/348 ;)
Jul 2, 2010
4,012 (1.47/day)
System Name PC
Processor AMD FX 8320E @4.3ghz
Motherboard Asrock 970 extreme3
Cooling Phanteks PH-TC12DX, 3 x NZXT FN 140mm, 1x NZXT FV V2 120mm
Memory 8GB Corsair Vengeance Blue 1600mhz
Video Card(s) ASUS R9 290 DCII-OC 4GB
Storage 128GB Kingston V200 SSD 1TB WD Blue, 750GB Maxtor
Display(s) LG 27MB85Z 27" 1440p
Case NZXT Source 340
Power Supply Thermaltake 675w
Mouse Logitech G500S
Keyboard Logitech G510S
Software Windows 8.1 64 bit
very interesting, now i know exactly where to O/C :), (i had to change my post as moving it made it not make sense)

EDIT: Moved again :banghead: (wasn't concentrating)
Dec 31, 2009
11,513 (3.96/day)
System Name Daily Driver
Processor 7900X 4.5GHz 10c/10t 1.15V.
Motherboard ASUS Prime X299 Deluxe
Cooling MCR320 + Kuplos Kryos NEXT CPU block
Memory GSkill Trident Z 4x8 GB DDR4 3600 MHz CL16
Video Card(s) EVGA GTX 1080 FTW3
Storage 512GB Patriot Hellfire, 512GB OCZ RD400, 640GB Caviar Black, 2TB Caviar Green
Display(s) Yamakasi 27" 2560x1440 IPS
Case Thermaltake P5
Power Supply EVGA 750W Supernova G2
Benchmark Scores Faster than most of you! Bet on it! :)
Nice to see some common knowledge in becnhing circles make it out to the public. Nice work!
Mar 6, 2008
2,700 (0.76/day)
System Name I Dub Thee Infinity
Processor Intel Core I7-3930K
Motherboard EVGA X79 Classified
Cooling Corsair H80
Memory 16GB GSkill Trident X
Video Card(s) EVGA GTX 980 Ti SC+
Storage SanDisk Ultra Plus 256GB, OCZ V2 180GB, 2x Toshiba X300 5TB RAID 0
Display(s) Acer XB270HU
Case Cooler Master HAF X
Audio Device(s) Creative X-Fi Titanium + Sennheiser HD 598 + Klipsch ProMedia 2.1
Power Supply EVGA 850W G2
Mouse Razer Naga 2014
Keyboard Gigabyte Osmium Cherry MX Brown
Software Windows 10 Pro x64
Very nice.