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A7N8X Dual Channel DDR

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May 6, 2003 12:06:29 PM

I built a new computer last week, here are my specs:

Asus A7N8X Deluxe Version 2.0
AMD Athlon XP 2500 333MHz FSB
1 stick of 512 Kingston value RAM PC2700 (333MHz)
ATI Radeon 8500DV

I just purchased another stick of Kingston 512 PC2700 and it should be here in two days. I've read things about the Dual Channel DDR support. How do I turn this on in the BIOS? Also Where should I put the two sticks of PC2700, in slots 1 & 2? Thanks in advance for the help!

More about : a7n8x dual channel ddr

May 6, 2003 1:06:12 PM

it's automatically enabled as long as you put them in the correct slots. Page 1-8 of the manual tell you how - either 1 & 3 or 2 & 3

<i>It's always the one thing you never suspected.</i>
May 6, 2003 2:20:03 PM

your Mobo can do 400 FSB (or will be able to soon with a new BIOS), so why not get the PC3200 (400 MHz) instead of PC2700 (333 MHz)?



XP 2800+ (thor B); Asus A7N8X Delux; Maxtor 40/120 gig ATA 133; AIW9700 RadeonPro; Corsair PC3200 (2X256); LiteOn CDRW; TDK 420N DVD+RW; Antec Case; Antec SL350; many many fans; WinXp
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May 6, 2003 2:38:39 PM

Yeah I bought PC2700 because my Athlon XP runs at 333MHz but now I wish I bought PC3200 becaue you cannot take advantage of the Dual Channel feature unless it's PC3200. I can't return my memory either, O well. What I'll probably do is wait for the first 400MHz Athlon XP chip to drop to around $120 (which will be a long time from now, I know) and at that time I'll buy two sticks of 512 PC3200.

Asus A7N8X Deluxe v2 -- AMD Athlon XP 2500 Barton Core -- 512 P2700 --
ATI Radeon 8500DV --- Using onboard audio -- Antec Plus660 AMG 330W case <P ID="edit"><FONT SIZE=-1><EM>Edited by mightymo on 05/06/03 10:45 AM.</EM></FONT></P>
May 6, 2003 2:43:34 PM

test

Asus A7N8X Deluxe v2 -- AMD Athlon XP 2500 Barton Core -- 512 P2700 -- ATI Radeon 8500DV --- Using onboard audio -- Antec Plus660 AMG 330W case
May 6, 2003 4:14:59 PM

Quote:
Yeah I bought PC2700 because my Athlon XP runs at 333MHz but now I wish I bought PC3200 becaue you cannot take advantage of the Dual Channel feature unless it's PC3200.

Whether Dual DDR is in effect or not in effect is not dependent on the memory speed. The offset memory slot has its' own channel and the other two - looks like they're close together - combine to make up the other channel. A memory controller for each each channel. As long as there is memory in both channels, Dual DDR is in effect.
May 6, 2003 4:29:40 PM

But the manual says this only works with PC3200. This raises a second question, I thought you get better performance when the Memory is in Sync with the Processor FSB speed. This is why I bought PC2700. If I do switch to PC3200 and make it run at 800MHz, would that be better than running at 333 in sync with the processor?

Asus A7N8X Deluxe v2 -- AMD Athlon XP 2500 Barton Core -- 512 P2700 --
ATI Radeon 8500DV -- Using onboard audio -- Antec Plus660 AMG 330W case
May 6, 2003 4:43:21 PM

Quote:
But the manual says this only works with PC3200.

If the manual says that Dual DDR is only possible with PC3200, then that is an error in the manual.
Quote:
This raises a second question, I thought you get better performance when the Memory is in Sync with the Processor FSB speed.

That is correct according to nVidia's Dual DDR Memory Architecture Technical Brief.
Quote:
This is why I bought PC2700. If I do switch to PC3200 and make it run at 800MHz, would that be better than running at 333 in sync with the processor?

The best configuration is the one you have now. Adding PC3200 (DDR400) memory and running it at 400MHz with a processor which is running at 333MHz FSB would introduce performance killing latency. In short, the way you have your system set up now is fine. :) 
May 6, 2003 5:04:35 PM

you cannot turn DDR off. if you have two sticks and put both in slots 1 and 2, then DDR will not be activated. BUT, DDR works with PC2700, you bet. You're still gonna have a fast system with a FSB of 333 MHx and memory running at 333MHz. As was posted before, put the sticks in slots 1, 3 or 2,3.

I had PC2700, and DDR worked. But I got PC3200 thinking my board would eventually run at 400MHz FSB. Unfortunately this aint gonna happen for me, unlike you, because 400 MHz FSB is only supported for Motherboards PCB rev. 2.0 and above. I have rev. 1.4

XP 2800+ (thor B); Asus A7N8X Delux; Maxtor 40/120 gig ATA 133; AIW9700 RadeonPro; Corsair PC3200 (2X256); LiteOn CDRW; TDK 420N DVD+RW; Antec Case; Antec SL350; many many fans; WinXp
May 6, 2003 5:24:49 PM

Thank you guys very very much. OK good, so I should keep my PC2700. So let's say I buy another PC2700 DIMM for a total of 1GB. You're saying to put it in slots 1 & 2 because it will stay at 333MHz, but if I put it in slots 1 & 3 OR 2 & 3 it will run at 667MHz and actually slow things down, do I have it? LOL Thanks again.

Asus A7N8X Deluxe v2 -- AMD Athlon XP 2500 Barton Core -- 512 P2700 --
ATI Radeon 8500DV -- Using onboard audio -- Antec Plus660 AMG 330W case
May 6, 2003 5:47:40 PM

* Put the 512MB memory module you have now in the offset memory slot (looks like it's standing alone) and put the 512MB memory module, which is on the way, in either of the two remaining memory slots. Basically, your goal is to balance the amount of memory accross the two channels.

* If you were to put both memory modules in one channel, then one memory controller would be doing all the work while the other memory controller sits idle. Which is not what we want. We want both memory controllers working together to increase bandwidth and decrease latency.
May 6, 2003 5:56:14 PM

Quote:
... 1 & 2 because it will stay at 333MHz, but if I put it in slots 1 & 3 OR 2 & 3 it will run at 667MHz and actually slow things down, do I have it?

Dual DDR doesn't increase the memory module's speed. The *memory system* is sped up because the work load put on the memory system is being shared by two memory controllers instead of one.
May 6, 2003 10:31:39 PM

Think you need a recap...

All memory used in this board is DDR and so is the FSB. The actual MHZ of the devices are half what is advertised (i.e. 333mhz is really 166mhz). This is because DDR (Double Data Rate) pushes 2 signals per clock cycle (hz) as opposed to 1 with Single Data Rate (SDR) so in theory DDR is twice as fast as SDR at a given frequency (MHZ) - The reason these devices are advertised at double the MHZ is just marketing.

As for dual channel, the Nforce2 chipset based boards have 2 memory controllers built in as opposed to the usual 1. Using 2 memory controllers allows for seperate memory banks to be read at once but this depends on where the memory banks are located - Memory controller 1 is connected to slots 1 and 2. Memory controler 2 is connected to slot 3. Therefore any combination of memory sticks in slot 1 and 2 will only allow for single channel operation while adding a second or third to slot 3 will automatically enable dual channel mode.

Also if your CPU is unlocked (as all thoroughbred B's seem to be) then you can increase the FSB speed while reducing the multiplier to obtain better performance at the same CPU speed and also better overclocking results. You'll want to keep your FSB and memory sync'd so you may find the speed of your ram limits your FSB speed.

Hope that helped more than it confused.

<b>Vorsprung durch Dontwerk</b>.....<i>as they say at VIA</i>
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