HELP: Very slow memory throughput with new KD7

Timothy Miller · Jul 16, 2003

I recently bought a KD7, and I'm having a few problems with it. I hope you can please help me with them.

According to the BIOS screen, the board model I have is KT400-8235-6A6LYA1AC-DN. I have an Athlon XP 2800+ (barton core, 333mhz fsb) with 1 GIG of PC2700 DDR. The board has AwardBIOS.

The Corsair memory I'm using turns out to be from SpecTek, which uses Micron silicon. I called SpecTek to get a datasheet, and they directed me to the data sheet for Micron MT46V64M4TG-6T.

I use the following settings for memory:

CAS latency: 2.5
Bank Interleave: 4
Trp: 3T
Tras: 7T
Trcd: 3T
Drive strength and controls are all Auto
DRAM Access: 3T
Enhance DRAM Performance: Disabled
DRAM Command Rate: 1T
Write Recovery Time: 3T
tWTR: 1T

The first problem that I encountered was that I seem to be getting unusually low memory throughput. Using "memtest86", I get 665mb/sec. Using STREAM under Linux, I get closer to 1040 mb/sec peak. Doing some searches on google has revealed that most people get closer to their peak bandwidth, so, I should be expecting at least 2400 from STREAM, judging from the numbers others are getting. I know in the real world, you never get peak, but in synthetic tests, I should not be getting half the rated bandwidth.

If you could please help me to figure out what is slowing things down, I would appreciate it very much.

When working to determine what might be amiss, I decided to flash the latest BIOS. After following the directions exactly, I went into the BIOS settings and restored all of the settings to what they had been before I flashed the BIOS. The machine would not POST. After some tinkering, it seems to be "Fast CPU command decode" which causes the machine to not POST. (This is the case, even if it's the only setting I change, with everything else being default values.) This setting worked before, so what changed to break it? Should "fast command decode" not work with my system?

Thank you.

- HAL9000 · Jul 17, 2003

Is your ram clock set for 166?

Forrest

Motherboard Help By HAL web site:
http://home.attbi.com/~hal-9000/

On 16 Jul 2003 09:52:43 -0700, (Timothy Miller)
wrote:

I recently bought a KD7, and I'm having a few problems with it. I hope you can please help me with them.

According to the BIOS screen, the board model I have is KT400-8235-6A6LYA1AC-DN. I have an Athlon XP 2800+ (barton core, 333mhz fsb) with 1 GIG of PC2700 DDR. The board has AwardBIOS.

The Corsair memory I'm using turns out to be from SpecTek, which uses Micron silicon. I called SpecTek to get a datasheet, and they directed me to the data sheet for Micron MT46V64M4TG-6T.

I use the following settings for memory:
...

Timothy Miller · Jul 17, 2003

- HAL9000 wrote:

Is your ram clock set for 166?

Forrest

Motherboard Help By HAL web site:
http://home.attbi.com/~hal-9000/

Thanks for the response. The clock is indeed set to 166, and when I boot, the POST screen says that it's using DDR 333. Also, it gets the CPU model number correct.

Something very odd is going on to kill my memory performance.

David (30) · Jul 17, 2003

- HAL9000 wrote:

Is your ram clock set for 166?

Forrest

Motherboard Help By HAL web site:
http://home.attbi.com/~hal-9000/

On 16 Jul 2003 09:52:43 -0700, (Timothy Miller) wrote:

...

If your system allows it, try the following settings at 166 MHz:

CAS latency: 2
Bank Interleave: 4
Trp: 2T
Tras: 6T
Trcd: 2T
Drive strength and controls - Set to HIGH instead of Auto on all banks if unstable with above settings DRAM Access: 2T Enhance DRAM Performance: Disabled
DRAM Command Rate: 1T
Write Recovery Time: 3T
tWTR: 1T

- HAL9000 · Jul 18, 2003

Oh yea, reference your earlier question. Seems like someone said fast command decode only works when the FSB is 100. May want to do google search if you want more info.

http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&group=alt.comp.periphs.mainboard.abit

You were talking about ram clock and not fsb clock, right?

Here is a far fetched one... Is there any chance you have upgraded the bios and then not reset it afterwards?

Forrest

Motherboard Help By HAL web site:
http://home.attbi.com/~hal-9000/

On 17 Jul 2003 07:47:50 -0700, (Timothy Miller)
wrote:

- HAL9000 wrote:
Is your ram clock set for 166?

Forrest

Motherboard Help By HAL web site:
http://home.attbi.com/~hal-9000/

Thanks for the response. The clock is indeed set to 166, and when I boot, the POST screen says that it's using DDR 333. Also, it gets the CPU model number correct. ...

Timothy Miller · Jul 18, 2003

David wrote:

If your system allows it, try the following settings at 166 MHz:

CAS latency: 2
Bank Interleave: 4
Trp: 2T
Tras: 6T
Trcd: 2T
Drive strength and controls - Set to HIGH instead of Auto on all banks if unstable with above settings
DRAM Access: 2T
Enhance DRAM Performance: Disabled
DRAM Command Rate: 1T
...

I have the datasheet on the RAM chips, and your changes (CAS, Trp, Tras, Trcd) would be running it out of spec. But I'm sure you know this. In any event, according to this article, making those changes won't affect it much, and CERTAINLY won't increase throughput by a factor of two:

http://www.techwarelabs.com/reviews/memory/memory_timings/index.shtml

According to the article:
"The memory timings on our particular setup that had the most impact on performance involved setting the Bank Interleave to 4 Way, decreasing the DRAM command rate to 1T, and decreasing tRCD to 1T [sic, they mean 2T]."

I think maybe I'll try your suggestion anyhow.

Drive strength will affect signals between the northbridge and the RAMs, but it isn't going to do anything about instability due to running RAMs out of spec. In this case, we're dealing simply with signal delays inside of a chip. One way to deal with THAT is to increase the supply voltage, but I'm not sure if I want to do that.

My situation is this: I want a stable system. I could see a few percent drop in performance due to some conservative settings, but I they surely would not cut the performance in half.

Thanks.

Timothy Miller · Jul 18, 2003

- HAL9000 wrote:

Oh yea, reference your earlier question. Seems like someone said fast command decode only works when the FSB is 100. May want to do google search if you want more info.

http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&group=alt.comp.periphs.mainboard.abit

Will do, thank you.

You were talking about ram clock and not fsb clock, right?

Both, actually. Both are set to 166. The BIOS recognizes my CPU as an Athlon XP, so I simply told it that I had a "2800+(333)". Additionally, in the memory settings, I have told it manually that the clock is 166mhz.

Here is a far fetched one... Is there any chance you have upgraded the bios and then not reset it afterwards?

I did reset it. And since setting "fast command decode" caused the system to not POST, I have reset it more than once. You're talking about moving that little CCMOS jumper next to the battery over, leaving it for 1 minute, then putting it back, right?

Thanks!

Timothy Miller · Jul 18, 2003

David wrote:

CAS latency: 2
Bank Interleave: 4
Trp: 2T
Tras: 6T
Trcd: 2T
Drive strength and controls - Set to HIGH instead of Auto on all banks if unstable with above settings
DRAM Access: 2T
Enhance DRAM Performance: Disabled
DRAM Command Rate: 1T
Write Recovery Time: 3T
tWTR: 1T

I tried your suggestion. memtest86 performance went up from around 650 to 725. STREAM performance went up by about 100 megs/sec.

I'm still nowhere near where I'd expect to be.

I lothe to do this, but I do have a spare disk lying around. I could install Windows and run SANDRA. It may be that it does a better job, or it may be that it inflates scores.

- HAL9000 · Jul 19, 2003

That's the one. Of course the computer needs to be unplugged while your doing this.

Forrest

Motherboard Help By HAL web site:
http://home.attbi.com/~hal-9000/

On 18 Jul 2003 07:58:55 -0700, (Timothy Miller)
wrote:

< snip >

I did reset it. And since setting "fast command decode" caused the system to not POST, I have reset it more than once. You're talking about moving that little CCMOS jumper next to the battery over, leaving it for 1 minute, then putting it back, right?

Thanks!

John TL Lee · Aug 13, 2003

Make sure you clear your CMOS after you flash yer bios.

"- HAL9000" wrote:

Is your ram clock set for 166?

Forrest

Motherboard Help By HAL web site:
http://home.attbi.com/~hal-9000/

On 16 Jul 2003 09:52:43 -0700, (Timothy Miller) wrote:

I recently bought a KD7, and I'm having a few problems with it. I ...