The Gigabyte GA-X48T-DQ6 - Redefining the High End?
by Rajinder Gill on January 2, 2008 3:15 AM EST- Posted in
- Motherboards
More BIOS Details
Command Rate (CMD)
The options are Auto, 1N and 2N. A setting of 1N can be used almost exclusively while overclocking, bringing a performance advantage of around 2ns to memory access latency. If memory speeds over DDR3-1800 are desired then a setting of 2N may be required for stability.
CPU/PCI-E Clock Driving Control
The default setting is 800mv, with a range of voltage control offered between 700mv-1000mv. As this is a differential amplifier circuit, increasing voltage may actually decrease the clock signal accuracy due to increased power supply noise. Differential circuits are used in preference to single ended circuits because of their noise rejection and low voltage operating capabilities. Increasing voltage to these circuits in turn increases "nasties" such as overshoot and output clock signal jitter. This in turn counteracts the benefits of using a differential amplifier in the first place. We did experiment with various levels of overvoltage and found no gains in stability whatsoever, further cementing our beliefs that more is not always better.
CPU Clock Skew Control and (G)MCH Clock Skew Control
These two clock skew settings are directly related to the voltage control circuit above. They control the PLL output to both the CPU and Northbridge. Again, as a differential amplifier is used, the level of offset required should never exceed 150ps (Pico seconds) of skew to either the CPU or Northbridge reference clocks. At most, PLL circuits such as these should be "good enough" to retain a jitter level of around 150-200ps (lower is better). For those wishing to experiment, adjustments in the range of 0-200ps are of interest for both of the clock skew functions. As a rule, start with the lowest voltage possible, tune either skew setting, and then monitor for effects if any.
DDR3 Overvoltage Control
Base VDimm is 1.5V. The scale offers between 1.5V-3.05V, more than enough to fry any DDR3 modules. 3.05V is certainly more than enough voltage for extreme benchmarking.
PCI-E Overvoltage Control
This sets
a level of overvoltage to the PCI-E bus. The available voltage range is between
1.5V-2.25V. We recommend staying close to stock voltage; higher voltages cause the
board to shut down during the boot cycle. Most modern graphics cards do not benefit
from higher PCI-E voltages. Increasing this voltage will increase noise and magnetic interference into nearby sensitive circuits. Remember, more voltage always has side effects, it is best to let graphics cards draw their power from the PSU PCI/E connectors rather than through the motherboard.
FSB Overvoltage Control
This voltage setting is more commonly known as VTT. Default is 1.10V, with a maximum of 1.41V available. This voltage is critical for quad-core overclocking. 400FSB will require 1.41V right off the bat if stability is desired. (Ed: When isn't that the goal?) Unfortunately, we have no direct control over GTL (Gunning Transceiver Logic) reference values, which are locked at 67% of VTT for CPU die 1 and 63% of VTT for CPU die 2. On a top-end board like this, we had expected to find GTL adjustments, which can be crucial for finding quad-core CPU stability at high FSB speeds.
(G)MCH Overvoltage Control
Default voltage is 1.45V, and the available voltage scale provides an overvoltage of 0.025-0.775V. There an actual undervoltage of 0.2V from the BIOS set overvoltage. For example, as the stock voltage is set to 1.45V a BIOS setting of +0.50V would imply a voltage of 1.95V. However setting +0.50V gives an actual voltage of 1.75V, suggesting an undervoltage of 0.2V.
Loadline Calibration
Setting this to Enabled reduces Intel's specification voltage droop to the CPU when significant power is drawn. Setting enabled places more strain on the PWM circuit and increases voltage overshoot (within the corrective feedback loop) and settling time from load oscillation, which in turn can affect CPU overclock stability. The trade off is that disabling this setting will require a higher Vcore increasing idle CPU temperatures. Vdroop under load is in the region of 0.06V. Therefore, if a full load voltage of 1.35V is required for stability, a setting of 1.41V will be required for Vcore with Loadline Calibration set to Disabled. The Enabled setting gives a Vdroop of around ~0.02V under load. Users are advised to pick a method that suits their cooling, and use common sense to work out how much voltage is safe at idle if Loadline Calibration is set to Disabled.
CPU Voltage
A range from 0.50V to 2.35V is available, making this board suitable for every type of perceivable over and underclocking. Please note we have not experimented with voltages higher than 1.90V with our cascades cooling, so we cannot guarantee voltages over 1.90V actually work.
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Frumious1 - Thursday, January 3, 2008 - link
What are you, the jilted lover of Raja or something? Seriously, I can't say I blame the AT crew for taking a break. Me and my family certainly did our fair share of slacking off over the holidays.Merry Christmas, Foxy Scrooge....
8steve8 - Wednesday, January 2, 2008 - link
i just got 8gb od ddr2 800 1.8v for $180 shipped from newegg.8GB of DDR3 costs $1,150 shipped from newegg...
thats not at typo.
DDR3 is irrelevant for now.
10x cost for 3% perf boost...
I'm not even going to read this review.
Kougar - Wednesday, January 2, 2008 - link
This makes no sense. Gigabyte offers GTL controls on the P31-DS3L, values are: 0.636, 0.603, 0.566, 0.54. Why offer them on a $80 budget board but not a ~$300 X48T end-of-the-world board?? I was expecting them to be there when I heard about the redesign.This was a great review, and I am still reading/rereading it to absorb the info. I had a few questions though... You said FSB Overvoltage control requires 1.4v for both processors, and stock is 1.15v?? I never touched this setting by more than +1 with my Q6600, but it might explain a few things. How or where did you find out what the stock VTT value was, as I wish to be able to look up this info myself for future reference and check the P35 version.
Rajinder Gill - Wednesday, January 2, 2008 - link
I used a DMM and probed both the supply mosfet and GTL transistors.Regards
Raja
Kougar - Wednesday, January 2, 2008 - link
Thanks for your reply! Are there any guides or what do you recommend for novice multimeter users trying to discern which mainboard components power what. I don't mind doing the research, I just need a pointer at where to get started. I have tried before but was not sure if I was measuring the correct components.Just for proof, here is a screenie of the P31 DS3L $75 board's GTLREF menu: http://i111.photobucket.com/albums/n129/Chanur64/I...">http://i111.photobucket.com/albums/n129/Chanur64/I...
I can't fathom why the X48-DQ6 lacks this, could they be waiting to add it in later when the BIOS is more mature?
PLaYaHaTeD - Wednesday, January 2, 2008 - link
Since nobody cares to ask, I will go ahead:When can we buy an X48 Motherboard, along with a Q9450 cpu? How can you give such a comprehensive preview, and talk about recommendations without addressing a release date?
If some of the rumors are true about X48/Wolfdale/Yorkfield being delayed to possibly march, then wouldn't it be irrelevant to speak about recommending this product 2-3 months before it will even be available?
Gary Key - Friday, January 4, 2008 - link
ETA of the X48 boards is unknown. They are ready, from a BIOS viewpoint the Gigabyte boards need some more work but the ASUS boards that will be reviewed next week are about 97% there. Boards have been manufactured by all of the majors, it is up to Intel to pull the trigger. It was going to be in December, moved to 1/7/08, moved to 1/21/08, and is now in a holding pattern waiting on X38 stocks to clear out to some degree, which is surprising as most of the suppliers will move X38 downward to replace the mid-market P35 boards.The Q9450 and others will be announced shortly and official launch dates will be available at that time. Once again, up to Intel, but after the Phenom launch, they have no real reason to hurry up. The reason for the previews is provide just that, a preview, but we were expecting (along with Gigabyte/ASUS/MSI) that boards would be launched by the 21st of this month.
minimeat - Wednesday, January 2, 2008 - link
Good review on the BIOS features, i've been looking for this kind of detail for each timing number to be explained for a while, as none of this information is in the Gigabyte manual for any of their motherboards (HINT HINT).Anyways, you forgot to explain one really important number that i have been wondering about for a while, the Refresh to ACT Delay. Can someone please explain this number, either update the review or post it here, it would be much appreciated. I noticed that they had it set to 60 in the review, and there is no Auto option inherent in the motherboard's bios for this number, and i have no clue what it does. Thanks!
Glenn - Wednesday, January 2, 2008 - link
Looks like Anands crew spent plenty of time with this board! Amazing that no comparison benchmarks are shown against more mainstream boards like 965s, P35s or some AMD flavors? All that work with very little usefullness outside of early adoptee's!Gary Key - Friday, January 4, 2008 - link
Hi,We will have a Intel chipset comparison roundup the week of the 28th, maybe earlier if Intel decides to launch this product according to the last timeline. We will have the ASUS X48 boards up next week with a very detailed MCH overview and the MSI X48 board the week after with some Quad CrossFire loving if the drivers make it. These previews are concentrating on getting the most out of the board, the roundup will concentrate on comparisons to other available products.