RAM: dual channel to single channel speed downgrade

[ikonia]

Hi,

I've needed to put some additional RAM in my machine hosting virtual machines.

It was previously running 2 x512 RAM. DDR400 ram. (Crucial Balistix)

I've just purchased 2 x 2 x 1GB sticks of Crucial DD4 400 RAM.


Now I'm running mem test with the 512 x 2 RAM in and 1 of the 1 GB sticks in (I'm running through them one at a time to just test them)

I notice with the 3 sticks in it obviously down grades the 2 x 512 from dual channel 128 bit - to single channel 64 bit - fine.

However I also notice that the ram is running at 100 mhz DDR200 which is a massive drop off.

Could someone explain if this is the expected behaviour ?
Would putting all 4 1 GB sticks in bring this back up to DDR400 ? running at the correct speed ?

I'm not good at understanding all the memory configurations so please expalin in simple terms.

thanks.

[scrandman]

It would help if you told us some details about your system...

[Agent]

It shouldnt do that at all. Have you tried manual adjusting it back mate ?
System specs would help though

[ikonia]

well,

i've given you the ram sizes/speeds,

this is running on an asus a8v deleux.

I understand the downgrade from dual to single channel, from 128 to 64 bit - but what I don't understand is the 100mhz/ddr200 downgrade ?

[ikonia]

I've not tried manually adjusting anything simpley because a.) I am not comfortable with all the memory speed stuff so don't want to mess it up b.) auto has always worked well when it was running in a sraight 2 sim dual channel setup

[Yellowbeard]

Check your manual. I don't think the A8V MOBOs support 3 DIMMs. You need to use 1,2, or 4 DIMMs. What is happening, is that you are asking 1 memory channel to operate in single channel and the other to operate in dual channel which this chipset cannot do and maintain stock speed. Most likely, the system will revert to 166mhz/DDR333 or 200mhz/DDR400 depending on your memory controller revision and chipset/bios revision.

I would suggest with 4 DIMMs that you raise the DIMM voltage to 2.6v or 2.7v.

[ikonia]

thank you for that.

I've just put the 2 new 2 x 1 GB pair in in dual channel mode and they are running great at 200mhz ddr400 - memtest is flying through.

Once I've ran a few passes of these I'll put the additional 2 x 1gb sticks in which should downgrade it to single channel but hopefully keep it at ddr 400.

thanks for the feedback.

[Yellowbeard]

Once I've ran a few passes of these I'll put the additional 2 x 1gb sticks in which should downgrade it to single channel but hopefully keep it at ddr 400.

thanks for the feedback.

With 4 DIMMs you will still have dual channel. However, based on the same limitations as above, ( CPU memory controller revision and chipset/bios limits) the bios may slow the system to CPU/166mhz and memory/DDR333 due to the extra loading of 4 DIMMs.

However, this is usually not a major slowdown if you "need" the 4gb of memory. Are your applications more memory intensive or CPU intensive? Also, you "might" be able to manually set the CPU and memory speeds back to 200/400 if this does happen and you need to regain the lost CPU speed.

[BUFF]

also remember that if you are on a 32-bit OS that you are only going to get ~3Gb as a big chunk of the last Gb will be reserved for addressing.

[ikonia]

on a 64bit system, but thanks for the nudge.

Its a poor mans development machine so it doesn't have to be lightning fast, but it will be faster than the ammount of disk paging its currently doing.

The drop off from DDR400 to DDR200 was amazing though just in the pace it dropped off in memtest.

[Yellowbeard]

but it will be faster than the ammount of disk paging its currently doing.
.

If the new memory does not resolve a sufficient amount of the page file activity, do you have more than 1 physical HD in the machine? If so, place your page file on a physically seperate disk from the OS. This usually helps with disk I/O bottleneck.

[ikonia]

disk layouts fine,

file system is spread out on 3 scsi disks so its not a problem.

the problem is simpley virtual machines are memory hungry and I don't have enough ram.

[Yellowbeard]

Sounds like a VERY nice system, especially now with the 4 DIMMs. I'm curious to know if the system reverts to DDR333 when you go with the 4 DIMMs. Also, when you go to 4gb you might have enable 4gb memory mapping. However, I have not used that board in quite a while so I don't remember if this is required or not.

[ikonia]

its a crap system, just used for hosting some virtual machines for some basic POC work.

With 4 dimms in it it scales it down to DDR200 running at 100mhz - very poor.

[Yellowbeard]

Is there anything in the manual about remapping for 4gb? I have never had to do this but, it may help the situation. It should either be a jumper setup on the MOBO or enabled in bios. Also, have you tried manually setting it to 166/333 or 200/400? And, I assume you have the latest bios. Also, what CPU do you have, and what core and stepping is it? CPU-Z can give you this info you don't know it off hand.

[ikonia]

nothing the manual about 4 GB mapping, I checked that after you initial suggestion (thank you).

I've not tried forcing the speed up as you have to set timings etc etc that I'm just not knowledgeable on, but I have put the extra power in you suggested.

Its an AMD X2 4200 not sure on the stepping. I can't run cpuz as this machine doesn't run Windows and its currently just running a mem test to make sure the ram is working fine.

I'm not THAT bothered as I suspect upping it to the 2gb from 1 will give the VM's enough ram to run better then I could etiher put the additional two in and take the slow down hit and assign more ram to the VM's or I could put the 2 in another machine thats currently running 1 GB for the same improvment.

This also means I'll be having 2 x 1GB Crucial Balsitix paired ram DDR500 for sale soon and 2 x 512 of the same for sale