Modding a Socket P CPU from 1066MHz FSB to 800MHz... how to proceed?

[KaoDome]

Hi! This is my first post here, so I'd like to thank you all for having me here as well .

I have an old Dell Inspiron 1520 laptop that came with a Core 2 Duo T7300, Merom, 65nm. Its FSB is at 800MHz so the best upgrade I could do to it would probably be a T9500, Penryn, 45nm.

I've seen online that the motherboard perfectly supports that processor so I'd already be happy with it. But I'm a tinker so I got me a cheap T9400 to do some tests, it's a Penryn era processor as well but it expects or is configured to use an FSB at 1066MHz. Searching around I found out that there's something called BSEL modding that's usually used to go to higher FSBs but there's the possibility of down as well.

In this case I think I have to isolate one of the CPU pins (as per the table in this post, and that ought to be enough. At least until I realize the microcode for the processor is not present in the BIOS and I would need to mod that too... Even thought I've been doing some reading all of this seems quite daunting to me because I don't understand some of the terms used in this kind of mods.

So for now this is what I've tried, I've put the chip in and tried to boot up just for the sake of it, which ended up with the laptop shutting down obviously. Then I tried to isolate (meaning... taping? disconnecting?) the BSEL1 pin with electrical tape to get it to use 200MHz increments. But these CPUs are still those that come with actual pins, i.e. with copper sticks coming out of it. So what happended was that upon putting the processor in its socket the pin actually punched through the tape, and I accomplished nothing. I thought of removing the pin altogether, but that sounds extreme... there ought to be a better way of doing it.

So my question is... could someone guide me through the process or point me in the right direction (maybe there's already a guide I couldn't find or some useful reads)? In any case this is just a test to see if 1066MHz FSB Penryns can work with the laptop, the idea is that I can mod this 5$ CPU and make it work I'd look into a more powerful one to repeat the process.

Thanks anyway for your time, and reading through all of this.

 

[danmur]

If you get the mod to work the 9.5x multi of the T9400 on an 800Mhz FSB will result in a 1.9Ghz frequency vs the 2.53Ghz frequency with the 1066Mhz FSB. Modding the T9900 3.06Ghz 1066Mhz FSB 11.5x multi to an 800Mhz FSB will result in a 2.3Ghz frequency making it slower than a T9300.

 

[KaoDome]

Thank you for explaining danmur! For some reason I thought they would keep running at those frequencies...

I'm going to go with the T9500 since it's 2.6GHz and that's already a good improvement on the T7300.

 

[Mr.Scott]

Just for future reference, you isolate the pin by painting it with clear nail polish.

 

[danmur]

Thank you for explaining danmur! For some reason I thought they would keep running at those frequencies...

I'm going to go with the T9500 since it's 2.6GHz and that's already a good improvement on the T7300.

No problem! The bus speed on an 800Mhz FSB is 200Mhz and on a 1066Mhz FSB is 266Mhz. The bus speed multiplied by the multiplier results in the clock frequency. So for the T9900 with a 1066Mhz FSB and 11.5x multiplier you take 266 x 11.5 and you get 3.06Ghz. If you were to get the T9900 to run on an 800Mhz FSB you'd have 200 x 11.5 = 2.3Ghz. With the T9500 you get 2.6Ghz which is even better than the T9900 running on an 800Mhz FSB!