Can someone explain the L12 mod to me?

I plan on picking up an Abit NF7-S and a Mobile AMD 2500+.
Now I want to run a 200fsb at least (depends on how much past that my memory will take). Then take the CPU higher by upping the multiplier.

Can someone tell me exactly what the L12 mod will do for my Mobile 2500+. Also, if any, what are the draw backs?

And last, could you post instructions or a link to instructions that tell me exactly how to do it and what pins to connect.

Thanks.

The L12 mod will change your default FSB from 166 to 200. No drawbacks that I can think of. The mod seems to help most on the NF7-S, though it can help with some other boards too.

Look in the AMD Abit motherboard section for instructions - there's a big sticky with tons of information about it.

Ok, but Mobile Athlons run at a default 133 FSB. So doing this mod would make it go to 200 or 166 default FSB?

You may want to read this summary:

Summary on overclocking the NF7-S rev 2.0 (with Tbred B 1700+ DLT3C and ...) (page 15)


It was done and written between July-Sept 03, but I think it should still be valid.

It was written for NF7-S rev 2.0 w/ Tbred B 1700+ DLT3C, but since then I moved to a mobile Barton and the FSB overclocking results remain unchanged.

The BIOS version written was upto 18, 20. Now there are newer BIOS version.

It also contains information about the L12 jumper mod to default FSB 166 and 200.


One thing I'd like to reiterate, FSB overclocking potential is intrinsic to the CPU internal circuits, motherboard, chipset and memory. It MAY not MAY NOT be related to the FSB L12 mod which is for setting some FSB Sense Signals to tell/trick the motherboard about what default FSB setting of the CPU should be.

I found that FSB L12 mod (or FSB_Sense mod) may or may not help the FSB overclocking at all (sometimes may be 0 MHz, sometime may be 10+ MHz). So I suggest getting the motherboard, CPU, good PC3200 memory module (at least), PSU, and set the system, FSB and CPU to run stable first and start from there.

Without any mod,
- the NF7-S rev 2.0 should do 220 MHz on average +- 10 MHz, and
- the mobile Barton should do 2.4 - 2.6 GHz on air with SLK level of air cooling.

CPU overclocking itself has little correlation with the FSB L12 mod.

To get higher than 230 MHz, that depends on many other factors, such as memory modules, Vdimm, and chipset cooling, .... The L12 may or may not help.

Thank you.
I've decided not to do the L12 mod right away. From reading a thread on doing the mod on mobile amd's I understand that you cannot go below a multiplier of 13, correct?

In that case I probably will not do the mod and just try to get my fsb and multiplier as high as possible.

gingo said:

Thank you.
I've decided not to do the L12 mod right away. From reading a thread on doing the mod on mobile amd's I understand that you cannot go below a multiplier of 13, correct?

In that case I probably will not do the mod and just try to get my fsb and multiplier as high as possible.

Click to expand...

I think should be FSB as high as possible and CPU as high as possible. Hence multiplier would be determined by CPU_frequency / FSB round to the nearby 0.5.

If you are using NF7-S rev 2.0, most likely you would end up something around, say

FSB = 220 MHz
CPU around 2.5 - 2.6 GHz
multiplier would be 11 or 11.5 or 12 (lower than x13)

Exact final setting of FSB and multiplier depends on final overclocking tunning.

gingo said:

Thank you.
I've decided not to do the L12 mod right away. From reading a thread on doing the mod on mobile amd's I understand that you cannot go below a multiplier of 13, correct?

In that case I probably will not do the mod and just try to get my fsb and multiplier as high as possible.

Click to expand...

You can go below a multiplier of 13 ... I think this has something to do with the BIOS revisions ... Abit used to have problems with this. I don't know if they still do or not, but if you use TicTac's modified bios, you will have access to the lower multipliers.

I have been running my NF7-S rev 2.0 with mulitplier lower than 13, with either a Tbred B 1700+ DLT3C or a Mobile Barton, using the regular ABIT supported BIOS's.

NF7-S rev2.0 is one of the nforce2 board that can access to both lower and higher multiplier for unlocked CPU's.

As said, if one can get the norm of 220 MHz FSB from it, a 12X would get the CPU to 2.6+ GHz, and a 12.5X would get to 2.75 GHz.