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How the tRAS value affects Memory Bandwidth on the nForce4 Chipset

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Josh_Hayes

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Aug 1, 2003
Location
Round Rock, TX
How the tRAS value affects Memory Bandwidth on the nForce4 Chipset : UPDATED

I did some Memory Bandwidth testing using Memtest86 v3.2 and wanted to know if others were getting roughly the same results.

Test setup :
AMD Athlon 64 FX-55 (2.6GHz) @ 1.385v
OCZ EL DDR PC-3200 Platinum Revision 2 @ 2.6v
Asus A8N-SLI Socket-939 Nforce4 Motherboard BIOS 1003.5b

Previous Conclusion :
On all nForce Chipsets, use a tRAS setting of 8,9, or 10 for Best Results.

Update :

I have done additional, extensive testing using the latest Beta BIOS (1003.5) for the Asus A8N-SLI which enables advanced RAM timings for the nForce 4.

I found that with the ability to change advanced timings in the BIOS, I get higher bandwidth with a lower Tras and Trc.

The new BIOS allows adjusting of the following values:

1T/2T Memory Timing
CAS Latency (Tcl)
RAS to CAS Delay (Trcd)
Min RAS Active Time (Tras)
Row Precharge Time (Trp)
Row Cycle Time (Trc)
Row Refresh Cycle Time (Trfc)
Write Recovery Time (Twr)
Read to Write Delay (Trwt)

I get best results at 200FSB of 1T-2-2-5-2-7-9-2-1, not the long recommended Tras of 8-10.


Code:
Tras	MB/s
5	2220
8	2172
10	2083

Test setup was as follows:

Tras 5 : 1T-2-2-5-2-7-9-2-1
Tras 8 : 1T-2-2-8-2-10-9-2-1
Tras 10 : 1T-2-2-10-2-12-9-2-1
 
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... sigh.

Very, very few people have NF4 setups as of today. Might want to wait a week or two for an answer. It is however the same results we've already seen with NF3 or even VIA, a setting of 10 is usually recommended for A64 platforms as the highest performing.
 
Yup, usually for me 8-10 is optimal.. and I have been getting good results with 00 also..
 
My nF3 gives similar results. 00, 5 & 6 all show higher bandwidth than 10 on my system. I would recommend that you redo your tests, though - your test setup shows that you kept trfc the same while adjusting trc. Trfc should be kept at trc + 2. That might influence your results. Just a thought.
 
KrisMCool said:
My nF3 gives similar results. 00, 5 & 6 all show higher bandwidth than 10 on my system. I would recommend that you redo your tests, though - your test setup shows that you kept trfc the same while adjusting trc. Trfc should be kept at trc + 2. That might influence your results. Just a thought.


I tested with the following settings...

Tras 5 : 1T-2-2-5-2-7-9-2-1
Tras 8 : 1T-2-2-8-2-10-9-2-1
Tras 10 : 1T-2-2-10-2-12-9-2-1

These are Tras + 2 :)
 
The best tras will also depend on the CPU multiplier your running so you may want to test that out a little as well in case people want to see the difference :)
 
From my understanding there shouldn't be any big differences between the chipsets, as the memory controller is on-die. However the BIOSes should matter.

I agree with KrisMCool that the other settings should be adjusted accordingly.

AFAIK these are the formulas for tRAS and tRC (bank cycle time)

tRAS = CAS + tRCD + 2 (CAS 2.5 equals 3)
tRC = tRAS + tRP
 
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