GTL Ref Tweaking Guide

[saaya]

Hey guys,

Been playing with Blackops and GTL Ref settings today and studdied the docs from Intel a bit. Its 10pm and i need to get some sleep, some quick points.

1. Core0 and Core2 are in the same chip? can anybody confirm?
2. Core1 and Core3 are in the same chip? can anybody confirm?
3. i meassured CPU GTL Ref volts, and the table i posted earlier is a bit off
4. 1 step is pretty much exactly 7mv
5. the BIOS maps VTT incorrectly! default vtt for 45nm cpus is 1.10v, which is applied by default, but its displayed as 1.20v. so when you use a 45nm cpu and set vtt to 1.30v its actually only 1.20v. That makes some fsb overclocks ive seen here even more amazing since they were actually with .10v vtt less!
6. this will be fixed in G33 thatll come out soon
7. Core1 GTL Ref is higher than the rest of the Cores by default, and is linked to NB Gtl!
8. Core0 2 and 3 was 720mv GTL Ref by default for me (which is 1.100v vtt x 0.655 instead of the official spec of x 0.635, its only slightly off tho, and it varies by board and cpu, so nothing special)
9. Core 1 has 760mv GTL Ref by default
10. Core1 always has 6 steps higher default GTL Ref, so when you set
    +10+10+10+10
    its actually
    +10+16+10+10
    this is per intel spec! so it should be like this on all boards...
    default per intel spec is
    Core0 0.635 x VTT
    Core1 0.700 x VTT
    Core2 0.635 x VTT
    Core3 0.635 x VTT
11. every board will have slightly different GLT Ref settings, with the same cpu, some boards will have a default GTL Ref +/- 30mv which is around 4 steps.
12. GTL Ref of Core0 2 and 3 should always be within +/- 5mv though since they are related according to intel spec

I made a little guide to show where to meassure GTL Ref voltages and how to calculate GTL Ref voltages easily for a given VTT

http://depositfiles.com/files/8755756
(kostenlos download -> download)



Here are some good guides explaining GTL Ref:
BlazingPC
EdgeOfStability