Memory Latency Impact on Performance
We just looked at the impact of memory bandwidth on performance, but what about latency? Let's first by adjusting the CAS latency from our default of 2 clocks up to 3 clocks. Almost all DDR400 these days is CAS 2 memory, but older memory may have a higher CAS latency or you may have to increase your CAS latency when overclocking to gain more memory bandwidth, so what kind of a performance hit is there when going from CAS 2 to CAS 3?
at_canals_08 |
at_coast_05 |
at_coast_12 |
at_prison_05 |
at_c17_12 |
|
Tcl = 2 |
116.12 |
140.43 |
123.37 |
113.69 |
83.15 |
Tcl = 3 |
115.52 |
137.07 |
121.91 |
113.37 |
79.92 |
At worst, CAS 2 memory seems to be about 5% faster than CAS 3 memory when looking at at_c17_12, our most CPU intensive test. While 5% alone isn't anything major, combine that with a number of other performance tweaks and they can definitely begin to add up.
Now let's look at keeping Tcl (CAS latency) fixed at 2 clocks, but vary Trcd timings from 3 up to 6 clocks:
at_canals_08 |
at_coast_05 |
at_coast_12 |
at_prison_05 |
at_c17_12 |
|
Trcd = 2 |
116.12 |
140.43 |
123.37 |
113.69 |
83.15 |
Trcd = 3 |
115.71 |
136.99 |
122.46 |
113.08 |
79.97 |
Trcd = 4 |
113.92 |
134.42 |
120.87 |
112.38 |
79.83 |
Trcd = 5 |
113.42 |
131.82 |
119.34 |
114.79 |
79.12 |
Trcd = 6 |
113.23 |
128.26 |
117.56 |
111.15 |
77.4 |
For the most part we saw no real changes when adjusting Trcd, the one exception being at_coast_05 which actually showed a pretty big difference between a Trcd value of 2 and higher latency values.
Next we'll look at adjusting Trp:
at_canals_08 |
at_coast_05 |
at_coast_12 |
at_prison_05 |
at_c17_12 |
|
Trp = 2 |
116.12 |
140.43 |
123.37 |
113.69 |
83.15 |
Trp = 3 |
115.6 |
139.24 |
123.13 |
116.35 |
82.09 |
Trp = 4 |
115.85 |
138.88 |
122.98 |
113.16 |
82.05 |
Trp = 5 |
114.84 |
138 |
122.65 |
112 |
80.98 |
Trp = 6 |
114.5 |
136.95 |
121.96 |
115.61 |
80.95 |
Here we see very little impact on performance.
Putting them all together we can see what the overall impact on using fast DDR400, higher latency DDR400 and extremely high latency DDR400 will be:
at_canals_08 |
at_coast_05 |
at_coast_12 |
at_prison_05 |
at_c17_12 |
|
2-2-2-10 |
116.12 |
140.43 |
123.37 |
113.69 |
83.15 |
3-3-3-10 |
114.47 |
134.11 |
120.64 |
112.62 |
80.56 |
3-6-6-10 |
110.74 |
123.76 |
114.75 |
112.17 |
73.8 |
Our standard 2-2-2-10 memory does actually offer reasonable performance benefits in Half Life 2 compared to DDR400 with higher timings such as 3-3-3-10 or the unrealistically high 3-6-6-10.
First and foremost Half Life 2 does appear to be rather dependent on memory bandwidth, but it is also quite appreciative of low latency memory as well. If you're wondering whether being able to run memory at low timings and high clock speeds is important, when it comes to Half Life 2 performance it is.
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drinkmorejava - Thursday, January 27, 2005 - link
When they test the Athlon 64 3400+, is it the 1meg clawhammer or the 512k newcastle. In comparisons with my friend who has a lousy newcastle with dual channel, he is always thoroughly beaten by my clawhammer.drinkmorejava - Thursday, January 27, 2005 - link
Zebo - Wednesday, January 26, 2005 - link
I wish y'all would do an expo of A64's incredible "feels faster" syndrome to to it's 1/3rd mem latency of all other platforms.bob661 - Wednesday, January 26, 2005 - link
#44Where can you buy it? Especially when MSI's website makes no mention of this.
Dranzerk - Wednesday, January 26, 2005 - link
#43Yes that is feature feature. MSI offers it, never saw it reviewed though.
miketheidiot - Wednesday, January 26, 2005 - link
#40, 42, their was talk a while back about a PCIe to agp adaptor. Not sure what happened with it though.bob661 - Wednesday, January 26, 2005 - link
#39The MSI board has no such feature. It would require a different MCP to get AGP to work or using one of the PCI slots to do it (which wouldn't be AGP).
bob661 - Wednesday, January 26, 2005 - link
#20I have some OCZ CAS3 DDR400 ram in my system. 7 months ago it was considered premium ram (it's EB3500).
Aquila76 - Wednesday, January 26, 2005 - link
#39 - WTF are you talking about? nForce 4 is only PCIe. What page are you looking at? I went through MSI's site and nothing on the Neo4 page says anything about AGP. There is no AGP slot on the mobo either. If you clcik on 'Special Features' that is for the special features of all of MSI's products.Dranzerk - Wednesday, January 26, 2005 - link
18 - Posted on Jan 26, 2005 at 12:35 PM by Phantronius said:"NF4 will not be supporting AGP bud, sorry, its PCI-E from here on out."
It does with a addon card..
http://www.zipzoomfly.com/jsp/ProductDetail.jsp?Pr...
MSI K8N neo4 Platnium NF4
GO to manufactor website listed on speical features:
Special Features:
ATX Form Factor
Supports Accelerated Graphic Port (AGP) Add-On Card
AGP on a NF4 tata!
:D