nForce 790i SLI Ultra - What do P1 and P2 BIOS Settings Do?

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nForce 790i SLI Ultra - What do P1 and P2 BIOS Settings Do?

Postby Apoptosis » Sun Aug 17, 2008 11:52 am

I've been trying to find out what these BIOS settings do for a long time now and am curious if anyone in the community here knows what they do. I've searched Google to death and have come to the conclusion that no one knows what it does... I've contacted memory companies and they aren't sure along with NVIDIA and motherboard makers..

I've come to the conclusion after reading that several of tier one sites also have no clue what this setting does. Read the comments on their sites about it. Anandtech, HardOCP, Xbit Labs, Firing Squad and more have no clue what it does. Anandtech even goes as far as saying NVIDIA refuses to provide information about these settings.

1) Firing Squad

It's also worth noting that the latest BIOS from NVIDIA features two obliquely documented settings: P1 and P2. Apparently, they both optimize certain timing settings in the 790i SPP. We found from OCZ, though, that enabling either setting will prevent stable operation at higher memory frequencies. They should thus be left at "Auto" rather than "Enabled."


2) Anandtech
Poor memory read performance above 475FSB unless you enable "P1" and "P2" which NVIDIA refuses to document operation of or provide information about.


3) HardOCP (Forum Post Between Daniel Dobrowolski of HardOCP and a Forum Member)

As long as I didn't touch the P1 and P2 settings I didn't have any issues with it.

Was this in the review?

It isn't. I actually didn't encounter data corruption at all messing with those two settings. What I did experience was instability and no improvement in overclockability. So I simply turned those off. However reading about those two settings I have learned that messing with them is one way to cause data corruption. I have not verified this myself.

The board is no longer in my posession so I'm not going to be able to verify that those two settings do in fact cause data corruption. So I'm relating something I've read in other forums and on other sites. I've read this several times so there may or may not be something to it.


4) XBit Labs

P1 and P2 parameters maybe set to Auto or Enabled. They appeared only in the latest BIOS version that is why there are no descriptions of these parameters in the paper and electronic mainboard manuals. And Memory Timing Setting parameter opens a separate page with adjustable memory timings.


5) OCXtreme

At the very bottom of this page before the Memory Timing Settings we see the elusive P1 and P2 options. These are the much discussed options that appear to be disabled at 475FSB and beyond resulting in horrible memory bandwidth.


Even EVGA doesn't say what the heck it does... All they say is this...

6) EVGA
The more recent BIOS's includes two new options that can boost memory performance. These options control internal timing parameters. These options can give a boost to performance at higher FSB and DDR speeds. A setting of "Auto" gives you the best overclocking possible. A setting of "Enabled" gives you the best performance possible.



Does anyone know exactly what the heck the P1 and P2 BIOS settings do?
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Re: nForce 790i SLI Ultra - What do P1 and P2 BIOS Settings Do?

Postby ratNukit » Sun Aug 17, 2008 1:20 pm

I heard someone say that over 475 FSB the board automaticaly adjusts the timings (sets higher timings for more overclocking) ignoring the user set timings, but if P1 and P2 are enable the timings are kept low, thus they cant be overclocked as high.
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Re: nForce 790i SLI Ultra - What do P1 and P2 BIOS Settings Do?

Postby DMB2000uk » Sun Aug 17, 2008 1:57 pm

This is part made up, part filling in the blanks, but from reading around it sounds like (to me at least) they are some sort of performance strap for memory, kind of like the Northbridge FSB Straps.

Makes sense as over a certain FSB limit it disables them as it's pushing the memory/memory controller too hard. And because of the disabling, they default to looser 'timings' so you loose out on the memory performance.

Forcing the straps from auto to the manual P1 and P2 keeps them tight.

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Re: nForce 790i SLI Ultra - What do P1 and P2 BIOS Settings Do?

Postby Apoptosis » Sun Aug 17, 2008 2:13 pm

I've had a couple responses from NVIDIA about it this afternoon. Here is one of them...


Those settings deal with enabling higher memory performance only when FSB speeds are above 1800MHz. They are essentially for overclockers.

I don't understand how they can affect memory stability at lower speeds. From what I understand, the FSB has to be cranked up before they work.
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Re: nForce 790i SLI Ultra - What do P1 and P2 BIOS Settings Do?

Postby Alathald » Sun Aug 17, 2008 4:13 pm

So, wait, not even NVIDIA knows exactly what they do? #-o
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Re: nForce 790i SLI Ultra - What do P1 and P2 BIOS Settings Do?

Postby Apoptosis » Mon Aug 18, 2008 12:08 am

Just got another response...
This is what we told press at launch for nForce 790i SLI Ultra:

The P1 and P2 BIOS options are for boosting memory performance for cases including high FSB speeds when overclocking DDR memory. These options control the internal timing parameters within the SPP. When tuned properly on a system, they can give a boost to memory performance at higher FSB and DDR speeds. For optimal memory performance, FSB and/or DDR overclock may need to be reduced such that the system can run stably with both options Enabled.

NOTE: Voltages must be manually configured when the P1 and P2 options are enabled. For the highest overclocking speeds possible, these options should be left at "Auto".
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Re: nForce 790i SLI Ultra - What do P1 and P2 BIOS Settings Do?

Postby Zertz » Thu Aug 21, 2008 8:01 pm

That response is so vague :roll:

They don't even seem to be sure themselves what the settings do :P
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Re: nForce 790i SLI Ultra - What do P1 and P2 BIOS Settings Do?

Postby Apoptosis » Thu Aug 21, 2008 9:10 pm

never did get a direct answer.. Go figure, but guess what... NVIDIA doesn't have a license to do QPI based chipsets for Core i7 and thus the Intel boards are coming to an end for them...
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Re: nForce 790i SLI Ultra - What do P1 and P2 BIOS Settings Do?

Postby martini161 » Thu Aug 21, 2008 10:05 pm

Nice! So they now either have to let Intel have SLI on their chipsets or lose most of the enthusiast market. good move by intel!
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Re: nForce 790i SLI Ultra - What do P1 and P2 BIOS Settings Do?

Postby Zertz » Fri Aug 22, 2008 8:04 pm

martini161 wrote:Nice! So they now either have to let Intel have SLI on their chipsets or lose most of the enthusiast market. good move by intel!


They can use the NF200 SLI bridge chip, but I'm not too sure vendors like ASUS and Gigabyte think this is a good solution. More PCB work, added cost...

nVidia will only be left with SLI on AMD, and neither AMD processors and nVidia chipsets for AMD CPUs seem to sell much so...
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