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Phoney DDR400 speed with AMD64 754pin MB ram > 1GB

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January 4, 2005 7:03:37 AM

This post contains a lot of information about a problem I discovered. I'll bet that many of you will want to test your actual ram speed after reading through this.

I realize that many 754 pin AMD 64 users only have 2 of those 3 ddr dimm slots on their single channel motherboard used. Have you looked at the actual speed measurement made by memtest86.com ver 3.2 for example?

Anyone with 2 Double Sided 1GB sticks for a total of 2GB actually getting DDR400 speed? How about anyone using 3 Single Sided 512MB sticks (Crucial makes these as a model 8T) for a total of 1.5GB. Are you getting a 1500+ reading for mem speed?

I'm using a 754 pin AMD 3400+ 64 with Nforce3 250 chips on my EPOX EP-8KDA3J motherboard with latest Bios. I have a contact with the same chip set in an MSI motherboard.

According to the EPOX manual, this board should maintain DDR400 (PC3200) speed with up to 3 single sided memory sticks inserted.

I purchased 3 Crucial 8T 512mb Single Sided sticks, as my contact was using two of these in their MSI board ok.

I use Memtest 3.2 for my memory speed measurements.

With a test PC2700 stick inserted, my mem speed shows about 1240MB/S, so I consider this to be the reference reading for DDR333 / PC2700 memory. This was only for reference and not used for the DDR400 speed qualification measurements.

With a single stick of a DS (double sided) OCZ or Geil PC3200 inserted, I get a mem speed of about 1560MB/s, so I consider this to be the speed readout for DDR400 / PC3200 memory.

With two of the SS crucial PC3200 sticks inserted, I do indeed read out the 1560 speed indicative of DDR400 speed.

However, when I insert the third SS stick, my mem speed drops to the 1240, indicaiting that the bios / hardware has rolled back the speed when the third SS stick is present, even though the EPOX manual claims there would be no such rollback.

As I mentioned, the epox manual says that the DDR400 speed is maintained with 3 SS dimms inserted. Also they do not claim that 2 sticks will give DDR400 speed unless at least one is SS stick. This is different from the MSI manual for the same Nforce3-250 chipset. Check out the manual at http://epox.com/USA/downloads.asp?class=MANUALS for my model EP-8KDA3J on page 3-7 where it explicitly says: "For 3 DIMM: Use SS DIMM on all 3 three slots for DDR400 speed."

The EPOX manual says that the DDR400 speed is also maintained when using one SS stick and one DS stick. This is logical (if it worked) since there would still be a total of only 3 sides connected on the parallel memory bus wires. However, in this condition, my memspeed drops to a lower speed reading than DDR333. With the OCZ memory I get 1060, and with the Geil I get 960. Again, this is with one DS PC3200 and one SS PC3200, a condition also promised by the EPOX manual to maintain DDR400 speed, but it's not measureing out that way.

My contact confirms that the MSI board does show the 1560 speed indicative of DDR400 with two of the same type of crucial sticks, be they don't have another stick to try and use all 3 slots. Also, the MSI manual seems to be a bit more forgiving, claiming DDR400 speed with two DS sticks inserted.

BTW, I've seen some really pricey 1GB DDR400 SS sticks, but they were like $400 each and outside the realm of most budgets. Based on what I've measured here, I could get 2GB memory with two SS DDR400 sticks for about $800, and probably maintain DDR400 speed.

NOTE: The optional non-automatic bios RAM timing settings don't prevent the speed rollback I'm reporting here. I can make the results slower, but not faster without inducing failure..

Okay, now the $64 question.

Does anyone with any AMD 64 754pin MotherBoard have some combination of memory that actually reads DDR400 speed with more than 1GB memory inserted, or all we all being hosed by the memory / chipset / motherboard / AMD vendors?

Athena
a b } Memory
January 4, 2005 7:58:56 AM

Supposedly the worst chipsets requiring rollbacks were the VIA and nForce3 150. Supposedly the nForce3 250 was better, and Anandtech showed the SiS 755 operating properly with 4 sides (2 double-sided DIMMs). But it's really up to the motherboard company what they do with BIOS. Also, the difference in memory stability for multiple banks is small between chipsets, because the memory controller is on the CPU (so there's little a company can do to make it more stable).

You could keep experimenting with more boards! Sorry, I just had to say that.

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<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>
January 4, 2005 6:12:14 PM

Thanks for the reply. So my question becomes:

Is anying with an AMD 64 754 board using 2each of 1MB DDR400 sticks and really getting DDR400 speed as measured by measurement utility such as memtest86.com that reads 1500+ if the memory system really is doing DDR400. If so, which motherboard, bios rev, and memory type? Same question for anyone using 3 each of 512mb DDR400.

Anyone also experience the speed reduction I'm seeing or am I all alone?

Thanks
Athena
January 4, 2005 9:22:10 PM

Doesnt windows have trouble handling 2GB of RAM? This could be the reason for the speed decrease.
January 4, 2005 9:51:27 PM

Thanks for the reply.

I didn't even try windows with that. All my testing with the >1GB memory was in memtest86.com ver 3.2 to see what the speed was and qualify if the memory system was working. Memtest 3.2 uses a linux kernel.

Athena
a b } Memory
January 5, 2005 1:24:22 AM

There's a timing issue, first seen in i875P chipsets and later on A64 chipsets, where the more banks you fill, the more likely you are to reach a stability limit. The solution? Better RAM. Another solution? Rollback the frequency. Since the second solution is done automatically by BIOS, sometimes you can't get around it.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>
January 5, 2005 2:12:04 AM

Yes, I understood that there are limits. I dillgently researched these limits prior to making this purchase. The limits I relied on were those stated in Epox's manual. The manual seems to be wrong.

It is a fraud to continue to publish the false information that 3xSS DDR400 will give DDR400 speed even though their Bios prevents this.

I spent extra money buying DDR400 memory that met their requirements. The requirements were false. The performance promised was false.

Now I am looking for something that works.

Anyone using >1GB on any A64 754 board at true DDR400 speed per a measurement (such as memtest86.com)? If so, what motherboard and memory are you using?

How about 939 boards?

Thanks
Athena
January 6, 2005 4:02:59 AM

I was just reading some more of my MOBO manual and realized that with what they recommend for memory configuration i probably can't have 3 sticks. Maximum config for ddr400 is 2 sticks. I was always under the impression that the more ram the better but now I am re-evaluating that position after reading a few things on this site and elsewhere. Specifically what Crash wrote.

Crashman Quote:
"If you planed on playing games, probably Windows XP? Windows XP isn't that great with memory management, 2GB tends to be SLOWER than 1GB, and 4GB can be problematic."

So anyone need an extra stick of 512 ddr400? hehehehe

AMD 64 3700+,ASUS K8N-E Deluxe-250gb,1.5 gb PC3200,Gigabyte GeForce 6800gt 256mb,Audigy 2 ZS , 2-36.7gb 10,000 rpm Raptors/Raid 0, Thermaltake butterfly 480 watt PSU , + asst. other amenities.....
!