VOGONS

Socket 370 FSB Pin Mod (B21/ BSEL)?

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First post, by j^aws

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Anyone succesfully complete a pin mod to force FSB on Socket 370 CPUs during POST?

Reading random threads from searches on the Internet, I found the image below advising on insulating/ removing BSEL (B21) pin to change FSB at POST.

Please see image below:

The attachment bsel-b21.png is no longer available

However, I think the image above has highlighted the wrong pin, and I've pencilled in green on what I think is the correct pin. This is based from the image below:

The attachment socket 370-bsel.png is no longer available

And this image is from an Intel datasheet (page 81):
http://download.intel.com/design/celeron/data … ts/24365820.pdf

Can someone confirm this is the right pin? Could I use the corresponding pin on an Ezra/ Ezra-T (VIA C3) CPU to achieve the same result?

What I'm trying to do is to force CPUs to POST at 66MHz FSB on certain boards that automatically detect 100MHz FSB. Some of my boards can POST 50/66 MHz FSB without any issues with dip-switches or BIOS settings. But I'd like to do this on all of my boards by pin-modding the CPUs as this seems the easiest trick.

Ironically, back in the day, modders were trying to achieve the opposite - forcing 100MHz FSB from 66MHz Celerons!

Reply 1 of 4, by Tetrium

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I found the Samuel datasheet here and the Nehemiah datasheet here

On the Samuel2 datasheet, page 30, it mentions what you'd need to do to achieve 66MHz FSB.
It mentions something particular about grounding both bsel0 and bsel1 pins? I'd say, just have a read.

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Reply 2 of 4, by j^aws

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Tetrium wrote:

I found the Samuel datasheet here and the Nehemiah datasheet here

On the Samuel2 datasheet, page 30, it mentions what you'd need to do to achieve 66MHz FSB.
It mentions something particular about grounding both bsel0 and bsel1 pins? I'd say, just have a read.

Thanks for the links. A quick read shows that both datasheets (P30 Samuel, P26 Nehemiah) show the same 66-133MHz configs using BSEL0/ BSEL1. And both also show (P44 Samuel, P54 Nehemiah) the same pinouts for BSEL0/ BSEL1 for PGA CPUs.

Regarding pins: Rather than modding the CPU pins directly (insulating or removing), would a simple switch setup using the BSEL0/ BSEL1 pins from behind the CPU socket, and connecting to ground on the motherboard be sufficient to control 66MHz selection?

Or, if using a Slocket/ Slotket, doing the same switch setup from these pins behind the CPU socket? This should make the setup more flexible.

Reply 4 of 4, by j^aws

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^^ Some of my boards already do this using BIOS/ jumpers, so this is for boards that don't. I'd rather mod these boards if I can, rather than discard them.

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