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Memory Questions

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Celeron_Phreak

Member
Joined
Mar 28, 2003
I'm fairly new to DDR memory, just started using a DDR system last fall and I must say....WOW. It's SOO much faster than SDRAM.

Anyway. I came here to ask some questions about it.

>>>First Question<<<
I have a stick of Mushkin 512MB PC3200, and then I have a stick of 512MB Centon PC3500 (haven't been able to find it anywhere since I bought it, not even on the net). They seem to run dual channel in my A7N8X. Putting them in slots 1 and 3, or 2 and 3 enables it. Now I've read that dual channel doesn't make much of a differance, if even one at all, withe AMD XPs, since the pipelines are soo close to the memory as it is, and Intel procs are further (so DC is better to use in Intel systems).

So I install the RAM in dual channel mode, and I was getting 36xx scores in 3Dmark03. If I didn't have them in DC mode, I get 35xx scores. So has this really improved much at all??



>>>Second Question<<<
I went through my BIOS settings and I noticed you can change a lot of the memory settings. Them being:

Memory Frequency
Memory Timing
SDRAM Active Precharge Delay [7]
SDRAM RAS to CAS Delay
SDRAM RAS Perchnge Delay [1]
SDRAM CAS Latency [2.5T]
FSB Speed Sprectrum
DDR Reference Voltage

Me being new to DDR and all the RAM stuff, have no idea as to what all this is used for. I looked at the memory sticky in these forums and I don't really want to buy a book right now, since I'm broke.

For the Memory Timing settings, you can change it to presets to User Defined, Optimal or Aggressive. Changing to Aggressive from optimal didn't change anything even the slightest bit, so I'm thinking maybe doing someting User Defined would help, but I have no idea how to configure memory timings without screwing something up.


If anyone could spread some light onto these subjects, I'd greatly appreciate it.

Thanks
~C.P.
 
Running in dual channel really doesn't make a big difference on socket a-platforms. Although the nForce2-chipset does have a 128-bit memory-controller, the FSB has only half the bandwidth, making it a bottleneck. Running in dual channel is actually known to hold back FSB-overclocking a bit, but as long as you gain a slight bandwidth increase, I recommend using dual channel. With nForce2, RAM and FSB should always run in sync.

For Intel platforms, things are quite different. They depend on high bandwidth in order to perform well, and the FSB and memory controller have the same capacity.

I don't know much about your memory sticks, but their rated timings should be found in the documentation. If not, you can check the manufacturers webpages, or use a program like SiSoft Sandra to learn more about them. What timings they can handle depend on their quality.

The basic memory settings are usually listed in the following order:
a) CAS Latency b) RAS to CAS c) RAS Precharge d) Active Precharge Delay

a) is usually 2.0 or 2.5, b) and c) should be 3 or 4 (sometimes 2)
d) is usually between 5 and 8, but should be set to 11 on nForce2-chipsets (regardless of memory quality)

Be aware that sometimes Active Precharge Delay is the second number
( a - d - b - c ), eg. 2.5, 8, 4, 4

If you want to know exactly what all these settings mean, I'm sure the sticky on memory timings would teach you a lot more than I can.

What FSB / multiplier are you running? If your FSB speed is default (333 MHz), perhaps you could even run at the tight 2.0, 2, 2, 11-timings (the best timings of all). When running memory underclocked, it's likely you will be able to tighten the timings, thus improving memory performance. However, high FSB speed gives a significant performance boost, despite the fact that one has to loosen the memory timings. This depends on your mobo's FSB-capacity.

All I know about FSB Spread Spectrum, is that it should be disabled when overclocking. I don't think it's necessary anyway (my sys runs just fine).
 
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I am running my chip at the auto detected settings. 166MHz (333) and 12.5 multiplier. Last night I played with memory timings while using the RAM in dual channel at 200MHz and it wouldn't POST, so I had to reset teh CMOS. Same thing when running the RAM in dual channel and at 166MHz. I'm thinking it doesn't like dual channel with the two differant types of RAM (one being PC3200 and the other being PC3500). I'm going to play with it some more tonight and see what I can do though.

Playing with memory timings at all in dual channel screws everything up and it won't POST. Even just by having the RAM in dual channel, changing the timing selector to user defined, and leaving all the settings as they would be in auto, STILL won't let it POST. I updated my BIOS last night, so we'll see what happens.
 
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