MCH Latch Frequency Confusion

[Salahuddin]

I would please like some help on MCH Latch Frequency. I recently purchased a Gigabyte GA-EP45-DS3L for a system I am putting together with a friend. This is paired up with an Intel E5200 and 2x2GB Buffalo Firestix rated at 5-5-5 at 1066MHZ.

I understand the MCH Latch Frequency to be similar to the FSB NB Strap. However, traditionally when I am OCing, I leave this setting to AUTO and OC the CPU and RAM independently of the NB strap. In my system, for example, my E6750 is OC'd to a FSB of 470 MHZ x 8 = 3.76 GHZ. I then selected the highest possible multiplier that would put my RAM around 1000 MHZ. This was 940MHZ at a 1:1 ratio.

With this system, I have OC'd the E5200 to a FSB of 280 MHZ x 12.5 = 3.5 GHZ. However, when choosing the RAM, I am given the option of selecting different RAM speeds based on the NB FSB speed. For example:

x.xxA = FSB 266 MHZ
x.xxB = FSB 333 MHZ
x.xxC = FSB 200 MHZ
x.xxD = FSB 400 MHZ

I can select a 3.33C (200MHZ NB FSB) multiplier and the system boots fine with the RAM at 930 MHZ in a 3:5 ratio.

However, if I select 3.33D (400MHZ NB FSB), which will also give me a RAM speed of 930 MHZ, the system will not post.

Similarly, even if I select 3.20B (333 MHZ NB FSB), which gives me a lower RAM speed of 896 MHZ, the system will fail to post.

It seems like the only two stable settings beyond 800 MHZ are 3.00A (266 MHZ NB FSB) which gives me a RAM speed of 840 MHZ and 3.33B (as mentioned above for 930 MHZ). This represented a ratio of 2:3 and 3:5 respectively.

So my questions are:

1. Why is the RAM frequency being linked to the NB FSB frequency?

2. How can I set my RAM to 1:1 or 5:6 to utilize the speed of my RAM more?

Please bear in mind that the system is being OC'd with stock cooling. I figure I should be able to get a 1GHZ OC with an E5200 without any significant problem.

[Leeghoofd]

1. Why is the RAM frequency being linked to the NB FSB frequency?

2. How can I set my RAM to 1:1 or 5:6 to utilize the speed of my RAM more?

1) Intel uses fixed dividers (1:1, 3:4,...) unlike with Nvidia where you got loads more dividers available (some think it's free adjustable on Nvidia : it's NOT )

Some dividers are better than other, some don't even post... I never got 400FSB with 1000Mhz ram speed working on my Maximus board on early biosses, it's your task to figure out wich dividers gives you the best performance...

2) I select 266 strap and put eg FSB to 333 or 400FSB and choose the ram speed accordingly... mess with the static read control, clock twister and PL levels to get max ram performance...soem boards prefer to use a divider instead of 1:1 to get lower PL performance, sometimes less ram speed is faster due to the lower strap selected... again testing and tweaking all the settings is a must to get the maximum performance out of it...

Eg if I select 266 strap on my P5Q Dlx and use 1000Mhz ram speed it's faster than 400FSB and 333 Strap and 1066Mhz ram speed... but on some other boards , other ram etc works differently...

[Salahuddin]

I'm a bit confused. If you select strap 266, how do you then choose FSB to 333 MHZ or 400 MHZ (isn't selecting the strap selecting the FSB)?

On my ASUS board, it appears that you can set up FSB NB Strap independently and then select RAM speed. I haven't really tested this out as I just leave the FSB NB on AUTO and things seem to work great.

With this Gigabyte board though, you are choosing RAM speed AND FSB NB Strap at the same time. If I select the 266 Strap (i.e. x.xxA), the only options I can select for RAM speed are x3.00A which is only a RAM speed of 840 MHZ or x4.00A which is 1120 MHZ (i.e. my RAM can't handle that). On the other hand, if I select 3.33B to get a faster RAM timing of 930MHZ, I'm using the lowest NB FSB at a 3:5 ratio!

I would have thought the most logical OC would run the RAM at 930MHZ in a 1:1 ratio. Why wouldn't the system be able to handle that?

On the ASUS board, I would just select 930MHZ as the RAM speed and it would automatically pick a 1:1 ratio.

[Leeghoofd]

You can select FSB yourself, otherwise the board determines the final speed of the CPU and not you. Final ram speed is derived by the Strap/FSB speed you have picked...

some examples on my P5Q Dlx

333FSB set : (with the E8600 with multi 10 totals 3.3ghz)

If I set Strap 266 : I have the choice between 835/1002 or 1335 ram speed
If I set Strap 333 : I have the choice between 667/800 or 1066 ram speed
If I set Strap 400 : I have the choice between 666/887 or 999 ram speed

400FSB set (with the E8600 with multi 10 totals 4ghz)

If I set Strap 266 : I have the choice between 1003 or 1203 ram speed
If I set Strap 333 : I have the choice between 800/961 or 1280 ram speed
If I set Strap 400 : I have the choice between 800/1066 or 1200 ram speed

So according the FSB you impose on the CPU and the selection of your preferred Strap, final ram speed is calculated via the according divider...

On my parents board with the E8600 I run 4Ghz daily (on air) with 266 strap; rams at 1003Mhz as it gives me better performance as the 400 Strap which runs the ram at 1066…

Last gigabyte board I build for a friend was the P35DS4, I have those running 400FSB too with ram at 1002Mhz on the Q6600 (8 multi though)... think you are mixing up some stuff... plz post a picture(s) of ya bios settings

[Sparda]

Probably you just confused by it name in the BIOS. They are the same.

Gigabyte BIOS : Asus BIOS
CPU Host Frequency : FSB Frequency >> Thing you like to play with
MCH Frequency Latch : FSB Strap to Northbridge >> Strap
System Memory Multiplier : DRAM Frequency >> Divider

In Gigabyte BIOS you just change the CPU Host Frequency to oc. Choose the strap. And it will automatically sort the divider in one row under System Memory Multiplier.
Then choose the divider according to your ram speed and the CPU Host Frequency you choose before. Easy peasy.
(Or you can choose the Straps and Divider first and change the CPU Host Frequency later)

If you cant post with the selected strap and divider just up your Static tRead Value (PL/tRD) or up the NB volt a little bit.

[Salahuddin]

Ah ok thanks guys. BTW, Sparda, I just got DMC 4 and its awesome

Can't post any picks right now as I'm running Prime95 on the system.

Basically though, my BIOS settings are as follows:

CPU Clock [x11]
Fine CPU Clock Ratio [0]
CPU Frequency 300x11 = 3300 MHZ

CPU Host Frequency [300]

MCH Latch Frequency [Auto]
System Memory Multiplier [3.33B] (B represents the 200 MHZ Strap) As mentioned, I could select 3.00A (the 266MHZ strap, but the RAM would be at 900MHZ which I think would be worse performance).

Memory Frequency 1000 MHZ

Timings are 5-5-5-18

After a few more hours of Prime, I'll try to see if 3.33D works by increasing the Static tRead Value. I tried increasing NB voltage before and it didn't change anything.

I think I was confused because Leeghoofd was picking FSB frequencies at exactly the same as the Strap frequencies (i.e. 333, 400), instead of some number like 350.

Basically though, in your example with the E8600, if it could clock to 10x400MHZ = 4GHZ, then it should be no problem to run 1066MHZ binned RAM at 1066MHZ on the 400MHZ strap should it? There would be no reason to have to choose the 200MHZ strap to do this, or would there be one?

[Salahuddin]

I raised the Static tRead Value all the way to 10 and the NB voltage to 1.2V. No luck with 400MHZ FSB.

I guess my two working options are to choose the 200MHZ NB Strap at 1000MHZ RAM speed or 266 NB Strap at 900MHZ RAM speed. I would approximate about the same performance from both.

[Leeghoofd]

you got 4gb of ram you prolly need more NB volts... also if possible set TRFC option to 55