Dual Channel Shenanigans with GA-N400 Pro 2

With the help from Paul on a previous thread regarding how to upgrade my
existing computer from 1 to 2 gigs, I purchased ONE 1-gig (single sided) PC
2700 Kingston KVR333X64C25/1G chip. My computer had 2- DDR 512mb PC2700
HyperX Kingston chips (double sided).

I placed the new chip in slot three and my computer would boot up, but it
would NOT see the additional 1gig of ram. I tried slot four with the same
results. I then removed both 512mb chips and placed the single 1gb chip in
slot one and the computer booted up with it recognizing 1gb of RAM. I then
put both 512mb chips in slots 2 and 3 and my computer booted up in Dual
Channel mode recognizing the 2gigs of memory.

In the BIOS I was running in Turbo mode with my two 512mb chips in slots one
and two, NON- Dual Channel and I had no problems with reboots or the Blue
screen. When I tried dual channel with the original two 512mb chips in slots
1 and 3, I could not get a stable PC. I therefore, decided not to use Dual
Channel with my original setup and placed both chips in slots 1 and 2
running in Turbo mode. I have been running this PC without any problems for
a year with this setup.

Now, with three chips in the computer, running in Dual Channel mode AND my
speed in BIOS reduced to NORMAL, I am having intermittent problems with a
Blue Screen, which requires me to turn the computer off from the power
switch. CTRL/ALT/DEL does not work.

Am I SOL as it relates to Dual Channel? It appears that the only way for me
to get 2 gigs of memory is to use slots 1 and 2 with 1gig chips in both
slots and run the PC in Non-Dual Channel mode.

 

Have you looked at the "percentage" setting for memory ? My Nforce2 board
offers "100%", "83%" and so on, and if my FSB is FSB400, that would give DDR400
and DDR333 respectively. By using a lower percentage setting, you can
drop the DRAM speed a bit, and repeat your tests.

Turbo, on some motherboards, sets CAS to CAS2. Which is not good, if the
RAM being used is actually a CAS3 product. Better to either allow
the BIOS to pick the (slowest) timing via an "Auto" setting for the timings,
or examine the three sticks, and work out the timing numbers yourself.

In terms of the relative speeds of the FSB and the memory, remember that
the processor FSB is 64 bits wide, while the two memory channels together
are 128 bits wide. The system is "balanced", if the memory runs at half the
rate of the FSB. For example, if you had the processor at FSB400, then two
DIMMs at DDR200 in dual channel, would have the same theoretical bandwidth.
So you can turn the memory down a bit, and try to get stability, and lose
a few percentage points in performance. It still helps to have the
memory subsystem a little faster than the theoretical balance point, since
the memory bus is not 100% efficient (has timing holes). But if you had to
run the FSB at FSB333 and the memory at DDR266 dual channel, that might
still be a viable solution.

Using a "non-CPC BIOS", otherwise known as "Command Rate 2T", is another
way to improve stability (at the expense again, of memory bandwidth). But
modded BIOS are not available for all boards.

You already know about the "single channel workaround", but that isn't
very useful when using three sticks. For three sticks, either drop the
memory clock, or find a "non-CPC" or non Command Per Clock version of the
BIOS.

Paul

 

Paul there is a utility with Gigabit called EasyTunes and this is what it
shows:
CPU FSB = 167, Mem Freq. = 334 (not adjustable up or down), Mem. Volt. 2.6
adjustable up to 2.8, not adjustable down to 2.5, AGP Freq. 67, AGP Volt.
1.5, PCI Freq. 33 and Ratio 13. My CPU is an AMD Barton 3000+.

I am not overclocking anything in BIOS that I am aware of. However, with the
previous setup with two 512mb chips there was a BIOS setting of Turbo that
worked just fine in non-dual channel mode.

 

Paul here's a response I just got back from Gigabyte:

"hello,
memory need to be same identical , to run 2G memory on dual channel mode :
put in 2 stick 1G identical memory on slot 1 and 3 should work ."

 

If it is a dual channel capable Nforce2 chipset, all that you need to do
is balance the total memory on the two channels. 2x512MB on one channel,
and the 1GB stick on the other channel, will give dual channel. The DIMM3
slot is the one that gets the 1GB module, while DIMM4 remains empty (and
DIMM4 would not exist on other brands of motherboards).

I've even done an experiment, where I got the source for memtest86+ and made
a trivial 3 line change to the program. I set up memtest86+ to measure the
memory bandwidth at eight different spots in the memory. I installed
3x512MB on purpose, as it is "unbalanced". What I discovered is, the
memory operated at dual channel speeds for 2/3rds of the memory, and at
single channel speed for the remaining 1/3rd of memory. So in fact, the
motherboard will operate in dual channel mode, for as much memory as
is "matching" on the two channels. Any left over memory (where one channel
has more memory than the other), is operated in single channel mode.

OK, while I was writing that, I download the manual from here.

http://america.giga-byte.com/FileList/Manual/motherboard_manual_7n400p2_e.pdf

PDF page 51, shows the "percentage" setting in the BIOS for memory. Try
a value like 83% and run your tests again.

I don't know anything about EasyTune. I did all my testing on my Asus
Nforce2 board, using the BIOS. Unless there is something wrong with the
hardware, dropping the clock on the memory (using the percentage setting),
should give you stability. The JEDEC spec for PC3200 suggests 2.6V as the
voltage to use, and I don't recommend more than 2.7V unless you know for
sure the memory is rated for more than that. Some memory cannot take a
lot of voltage, while other kinds can. The champ for voltage, is Winbond
BH-5, which people routinely ran at 3.3V. My Ballistix memory would be
toasted in seconds, at that voltage.

Paul

 

Paul I responded back to Gigabyte with this message:

"On pag 19 of your manual it clearly states that the configuration that I am
using should work. I have a SS in slot one, a DS in slot two and a DS in
slot three. The computer recognizes Dual Channel and boots up with no
errors.

The only place in the manual where it says that the memory chips MUST be of
the same type is at the bottom of page 19, but that is only if you are using
dimm3 and dimm4 at the same time, which I am not.

Please also note, that I could not get Dual Channel Mode to work reliably
when I had just two chips of the same type in slots one and three. My system
would lock up frequently as described earlier. So there is something else
going on here with either the FSB setting or the memory frequency.

In the Bios I NOW have things set to Manual and my FSB is set to 166 and the
frequency was set to 333. However, after booting up and looking at what
Easytunes says the settings are at, my FSB was set to 167 and the frequency
was 334. In Easytunes, I dialed the FSB down to 166, but my frequency went
down to 332, instead of 333 as I was expecting. I can not manually change
the frequency to 333 within Easytunes. I will run the machine at this
setting (FSB 166 and Frequency at 332) for a couple of days to see what
happens."

I have been in the BIOS and do see where I can dial up or down the %
setting. I currently have it at 100%. As stated above in my message to
Gigabyte, I'll see what develops with my settings at FSB 166 and Mem.
Frequency at 332. Thanks for all of your suggestions.

 

I have the same board and was using two 512 single sided for 1 gig dual
channel. I added a Kingston double sided 1 gig stick and now run at 2 gig
dual channel enabled. PC3200/400

Rudy

 

Have you tried removing the two 512 MB sticks and just running for a while
with the new 1 GB. It could be bad RAM.

Not all RAM will be compatible, just because it boots and is seen doesn't
mean everything is fine.