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Old October 9th, 2006, 07:28 PM   #1
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Asus P5B-Deluxe: Overclocking and Tweaking Guide

Simple guide to help get you set up and start overclocking your P5B motherboard.

Things not covered are sound, usb etc as they are enabled as users need.


Bios 0710 or later should be used. for this guide I am using 0711. Grab it here If you have the wifi version of the board make sure you download the version of the bios you need.

Some helpful tips.

it seems Asus have a little known tweak that resets the board. Basically all you do is power on the board with no CPU for 10 seconds and this resets the board to factory defaults. If you have a none boot for some reason this may be the fix you need.

Moving to the bios an explaination of the options and what to look for.

Advanced section options, all we are bothered about for overclocking is Jumper free configuration, CPU configuration and chipset.
You open Jumper free config and this is what you get.

Next option to look for is AI tuning, this is where the overclocking starts.

Set this to manual, this open up the bios still further.

Working down the list you will see:
CPU Frequency, once chosen just use the + or - option on the numeric keypad to push the FSB up for down, the limit is shown top right of the bios screen and is 100 to 650fsb. Real limit for most boards dual channel is 540ish at this time.
DRAM frequency is where you choose what speed the ram will run at, on the P5B this is directly linked to the CPU Frequency, so as you push up the CPU fsb the Dram frequency pushes up with it...a nice touch from Asus.

I have decided to explain the DRAM ratio's further into the artice so now we move onto:

PCI Express frequency.90 to 150MHZ is selectable, selecting 120 or so can add a healthy boost to PCIE bandwidth if the cards you have can run this frequency. This option needs to be tested thoroughly to see how much the video cards can stand.110 is usually very safe, 120 is starting to push it a little.
PCI Clock...just set this to 33.33 and forget about it.
Spread Spectrum is best disabled for overclocking.
Memory Voltage 1.8 to 2.45V, only supply the dimms the voltage they need to get the overclock or speed stable. I recomend no more than 2.5V for DDR2 maximum and with this board hitting 2.45V max you should be safe. Remember to cool the ram with a fan if you can.
CPU Vcore Voltage Auto sets the voltage the CPU is hard coded to set, I always set this and view the voltage in the hardware monitor section of bios so I know my start point. Remember more volts = more heat, on air cooling with C2D try to stay at under 1.5V, 1.6V with water and phase change cooling.
FSB termination Voltage useful option when pushing the FSB frequency high on the CPU, adding a little voltage here can help stabalise things as you clock higher.
NB Vcore Remember the memory controller is on the NorthBridge, adding some voltage here can have a huge impact on how well the CPU and memory overclock. Just remember if you set the max 1.65V to keep the NB cooled by adding a fan over the heatsink.
SB Vcore useful for adding extra voltage to the PCIE bus when overclcoking video cards and trying to run them on an overclocked PCIE frequency, I would tend to use 1.7v as a max here.
ICH chipset voltage I have found no need to alter this during testing, some say it adds stability, I set auto.

CPU Configuration page. I scrolled this down so you can see all the options in the pic. For overclocking you may want to drop the multiplier on the CPU an option or two, highlight the Modify ratio option and you see the following.

Now, not all C2D's are fully unlocked, some are partially unlocked so to see what you have available to tweak I highlighted where to look.

Remember to also set the following if you are adjusting Vcore and the ratio on the CPU.

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Old October 9th, 2006, 08:57 PM   #2
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Moving on its time to look at Northbridge Configuration

Once you enable this page you see the following.

The memory Remap feature is for when you are using 4GB of stsrem memory and XP, this option hardware maps the allocated ram from just over 2GB to just over 3GB with good performance, if you have only 2GB installed just leave this to disabled.

Configure DRAM timing by SPD
if you leave this option to auto it will read the timing tables off the modules and apply them to the memory during normal operation, issue is we have found Asus force a few timing options of their own and only partially use what is coded into the SPD, this is why we always recomend end users set their memory timings manually. To do this force the SPD option to Disabled

Once Disabled the page opens up to reveal the following.

Most everything you need is included, the following pics reveal all the options and where to look for the options available. Some require you to select the option and choose from a list, some require you just use the + - options once the field is highlighted.

Remember to initially set the default timings for your modules, usually manufacturers quote the timings in the following order...tCAS, tRCD, tRP and tRAS IE: 5-5-5-15. This just so happens to be the order of the top 4 options in the Asus P5B bios, so if you are unsure just work down the list setting what you see quoted on the dimms and you will be good to go.

Dram Write Recovery time 6 is ultra lose and good for high memory overclocks, 4 is about as tight as most dimms will go, keep this in mind as you test.

DRAM TRFC simple rule for this option. If your memory is Micron IC based you may be able to go as low as 20, everything else we have found 35 works best. Options are 20 25 30 35 and 42. obviously 42 is very lose and will allow higher overclocks.

TRRD Options 0 to 15, around 10 is where most leave this, no big effect on performance.
Rank Write to Read delay Real important timing, start at 10 some dimms may even need 12, tigher for more performance.
Read to Precharge delay again important timing, start at 10 with some dimms needing 12, tighter for more performance.
Write to precharge delay again another important sub timing, same rules..start at 10 or 12, tighter for more performance.
Static Read Control Disable for moderate to high overclocks.

Little further down

PEG Link Mode has a huge effect on video performance, I personnally leave to Auto, Fast and Faster for the brave.
Asus C.G.I if you are running Xfire (maybe SLI also) you need to enable this option as it looks to enable Peer to Peer writes which allows the Video cards to talk to each other.

last but not forgotten, South bridge chipset Configuration You are going to want to set 4X mode for best performance if running SLI or Xfire.

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Old October 10th, 2006, 02:03 PM   #3
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Memory controller issues you need to know.

For the i965 chipset to stand a chance of hitting high FSB speeds some clever manipulation of the chipset internal timings are needed. Most know Intel release CPU's with various default FSB speeds, the usual suspects are 533, 800 and 1067. Celerons are usually fixed on the 533 bus but should be moving soon to the 800, most other P4 775 CPU's are 800 bus speed apart from the older Extreme Edition and the new C2D CPU's that are based on the 1067FSB.

The CPU has a set of pins or dots on the base called the BSEL . These pins or dots actually tell the board what FSB to apply to the CPU and tell the chipset what strap to run. The strap is actually a set of ram ratio's and a clock muliplier along with an internal latency setting. Try to think of the northbridge pretty much like a uses a default frequency and a muliplier..and yes you can overclock it.In difference to a CPU though it also controls the memory and as such has internal latency settings that can be changed also.

Now....what you have to remember is as you push up the FSB on the CPU you also push up the FSB on the chipset. By default the chipset hits its max clock way before the CPU what do you do?

The answer is manipulate the chipset into thinking it is working with a CPU that has a higher FSB default speed.
How this is done is by altering the BSEL signals the chipset uses and by setting the undocumented(at this time) 1333 strap...this means the chipset thinks it is working with a CPU that has a base FSB speed of 333 (quad pumped is 1333)

Now Asus have been quite slick with the P5B range of boards as they allow the chipset to overclock quite a bit before they slow it down by altering the strap, what this means is that once slowed down by the 1333 strap it is already in an overclocked state. The bad part is that between 360 and 399fsb the chipset is massively overclocked and really does struggle some what, the consequence of this is an "FSB hole" where it is hard to get the board stable. In reality all you have to do to avoid this "hole" is set 400fsb or higher as the strap changes here to 1333 and the board takes off again usually all the way to 500+FSB. I explain more on what exactly is happening here in more detail.

What would be nice is the 1333 strap coming in at 360FSB but with the internal latency set using the 1067 strap which is faster than the 1333 latency setting, this would allow the board to work well up towards 399FSB.from 400FSB you would relax the latency setting to the 1333 default and allow the board to clock all the way to 500+ without the non usable hole we see at this time. hopefully if Asus see this article they will tweak the bios to set more like what I have quoted...but for now the board is an awesome overclocker as it is by default but it has this 1 quirk.
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Old October 10th, 2006, 03:33 PM   #4
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Memory Ratios

Default ratio's on the P5B range of boards, I added a small table along side the available options explaining how these ratios are made available.

Default 1067 strap has the following option available.
533,667,800 Or 1:1 (Sync with CPU FSB) 4:5 (async upclock) and 2:3 (async upclock)

By strap manipulation Asus have managed to add 2 options from the 800 strap which are 889 and 1067. 889 is 3:5 (async uplclock) and 1067 is 1:2(async upclock)

All should work fine with the CPU at default speed, the issue is they work very differently once you start overclocking.

If you are looking to run high FSB speeds then you really do want to stick with 533 or 667 mode. 800 will push the ram speed way to high normally.
If you are at stock speed you may want to try 889 or 1067, the reason for this is that these ratios are based off the 800 strap so the chipset is already running faster than it is when using the default 1067 strap memory ratio options. The downside though is the chipset will in no way overclock as well, infact some are right on their limit trying to run the memory in 1067 ratio and will error quite bad. 889 though is quite nice and does allow for some moderate overclocking. With the chipset running overclocked and a moderate overclock on the CPU you may find you have a wicked fast system, just remember we are not talking huge FSB speeds though...using a dram ratio taken from the 800 strap you are limited to moderate CPU and memory overclocking as the chipset is already overclocked with the CPU at stock speed.

There is 1 last tweak to be aware of...Often known as TURBO mode. Turbo mode takes chipset overclocking to the max, on a board like the P5B deluxe it would only run at the CPU's default speed. Turbo mode would involve forcing the chipset to run the 533 strap with the memory in 1:1. Using memory that is capable of tight latencies at DDR533 you would see performance from the board as if it was running memory at DDR1000 or higher. This would be due to ultra tight 533 based chipset latency and the fact that the memory controller would be massively overclocked.

The only downside is Asus usually limit this mode to default CPU speed, as soon as you set 1FSB over default the option turns its self off.

At this time I have not seen Turbo mode in the P5B bios, would be nice to see it appear soon though for the non-overclockers looking for a little system performance boost

I hope this small guide has been helpful, more guides are on the way as time allows, and board manufacturers send me boards (shamelss begging!!)

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