Now running Mobile Celeron (SL75J, 2400MHz 256Kb cache) and ASUS P4C800. MC has a default voltage of 1,3v, but in desktop board You get default voltage of 1,65 witch is way too high. I solved this simply bending VID4 pin flat outwards, now it defaults to 1,225v what is perfect.
Tried MC also with Soltek 845 board and no problems. Based on that MC might be running all socket 478 boards. (Edit: Abit has some shit on 865/875 boards, dont work on them)

MC is very cool processor, You can run it easy fanless, just normal P4 heatsink and some case cooling is enough, thermal guideline is only 35w!
http://processorfinder.intel.com/script ... CorSpd=ALL

Dualchannel board with FX5900 GS makes a quiet and powerfull gaming machine. I modified FX 5900 by replacing stock 2 fans with 95x95 fan running 1400rpm, very quiet too.

Edit: Forgot to mention My HDD, Toshiba 2,5" MK-4019GAX. Running 5400rpm with 16Mb cache helps keeping temps and noise down. Not to mention it is not too slow
http://www.toshiba-europe.com/storage/I ... =MK4019GAX

Just dont mix Mobile Celeron M and regular Mobile Celeron, first one dont fit to desktop board... yet, news are telling it might soon

Hmm, I was worried this was the "old" P4 Celeron with 128kb L2, but this is the new one with 256kb-- that's equivalent to the original <2.0ghz Williamette P4s before they went >2.0ghz Northwood (512kb L2). Performance should be decent.. I'd guess 2400mhz would be roughly on par with ~2.0ghz northwood, maybe a little better.

If possible get a P4-M instead of a celeron, afaik the celeron is even more limited with the p4 technology than the P3 celeron was.

Anyway I would recommend mobile CPU's to everyone reading this website.... thats if 2.4Ghz is powerful enough for u.

My first P4 was a 1.6Ghz P4-M, I was able to run it at 2.4Ghz with 1.38v which was around 45w, still lower than a standard P4 1.8Ghz.

Now im running a P4-M (D1-stepping) 2.4Ghz at stock speed, but I was able to run at 1.18v, watts are around 30w.
The difference in heat is amazing the CPU temp is a few degrees lower, but this is with a zalman CNPS7000A-Cu. I would say if I had a cooler worse than the zalman the temperature difference would be greater.
But the temperature difference to the heat inside the case, and the PSU exhaust and cover is huge.
I have no temperature probe to test it, but using my hand I can really feel the difference.
You wouldnt think a 15w difference in CPU heat can have such a drastic effect on heat in the entire system.

One problem I did have with my P4-M was the motherboard, its a gigabyte with a i865pe chipset. The bios locked me from running the memory at a 1:1 ratio with a FSB of 200 (800mhz).
So look away now if you are squemish about modding. I had to CUT a pin off the bottom of the CPU..... the only reason I had to do this was because of the motherboard.

P4-M is defaulting multipier to 12x with every desktop board, no matter original speed of processor. That makes some limitations in desktop use.
I am going to try also P4-M later this week, but there is much bigger "if" with this processor. Mobile Celeron is quite easy and it keeps multiplier as rated.

True the multiplier defaults to 12x, but im assuming must people would atleast buy a motherboard with some overclocking features to enable them to run at the normal speed.

Although not to most peoples taste, the Pin Mod made my CPU use 200 (800) FSB instead of the default 100 (400) FSB for all P4-M.

That means when I put my CPU into ANY desktop motherboard it will default to a 2.4Ghz 800FSB without any overclocking.

You cut BSEL1 pin?

Yep did it to two CPU's

To do the mod correctly you need to dowload the Intel Developer Datasheets for P4. This will show you the correct pins you need to cut.

A post in The Naked Review Forum provides a picture.
Using the picture from the forum link above, the pin I cut was 3rd down and 5 across.

To anyone trying this mod, be careful. I have bent most of the pins around the pin I was cutting, but these can be bent back.
I had this trouble with both processor, just pray that none of the bend pins break off.

Got My SL6VC today, cut BSEL1 pin and bend VID4. All went smooth, but My board dont see this as a 800fsb chip? Have to use manual selection.
No other probs thought. Vcore 1,225v by bios. Powerfull and very cool chip!
I used tiny srew driver bending BSEL1 until cut, no other pins were bend

Hi. Glad to hear it was a success! A good way of bending pins I found was to get a mechanical pencil, and (having retracted the pencil led inside) stick the CPU pin inside the tip. Then you can bend it back and forth in an easy and controlled manner without bending anything else

That pencil must be good! Nice tip

I've actually used retractable pens myself for just the same purpose. Zebra pens work well for me.

I've been watching this thread with great intrigue and now I'm hoping to get hold a few cheap mobile Pentium 4's off eBay it becomes a bit more relevant.

What's all this about cutting/bending pins?!? I've googled my heart out but can't find anything more on the subject. Am I right in assuming this would allow me to not only increase a P4's bus speed but also undervolt it? Would this still work on a motherboard that doesn't allow for undervolting in the BIOS?

Many thanks!
Will

Regular P4 has different VID (Voltage Identify Pin) order than Mobile P4. You can not bend VID pin, it have to be cut for lover voltage options if Your mobo does not give option to do it from bios. Most mopo´s dont have it.
There is 5 pins telling mobo what voltage Your processor wanna use, in Mobile P4 (and Mobile Celeron) this pin for ideal voltage happends to be on the outer pin line, therefore it can be bend, dont have to cut it if You dont want to.
BSEL1 pin have to be cut, there is no room to bend it down. This pin locks most mobo´s using higher than say 180MHz bus, not in all thought.

I HIGHLY recommend anyone who is ok with cutting a pin of the bottom of a mobile P4 CPU, to BUY ONE.

I just got a watt meter and at full load im at 91watts AC with 2.4ghz 800fsb 1.1875v 72 watts DC - PSU 19 watts of heat

I tried putting the vcore up to test it, at full load 127watts AC with 2.4ghz 800fsb 1.55v 101 watts DC - PSU 26 watts of heat

*Seasonic ST 80% efficiency, running two prime95 instances

What motherboards are you guys using? And how are you getting the Low VCore options? Do you have to cut 1 pin or 2?

Thanks...

Yeah, I'd love to know a good motherboard to get me started. Nothing cutting edge, just something to test all these cpu's before putting them in a CF-S969.

Storm's using a Gigabyte GA-8IPE1000 Pro and has replaced the active NB cooler with a passive Zalman cooler.

thanks ralf, too busy at work to reply.

I highly recommend a Gigabyte board, supported mobile CPU straight out of the box. Enough overclocking features to get the job done, and i was about to run at 1000fsb (but my memory cant run at 1:1 ratio). Undervolts to 1.0v I think. I would think most new Gigabyte boards will support a Mobile P4.

I have also tried an Aopen AX4SPE, work straight out of the box. But I recieved stability issues from this board, sometimes I would get a beep every 30 seconds from the onboard buzzer. The CPU temperature jumps around alot from 30 to 60 oC, from the aopen forums I think this is a big problem. These temperature jumps made the SilentTek useless because the fans would turn on/off or rev up/down every few seconds.

A friend has a Asus P4C800-E Deluxe, a bios upgrade was needed to get his Mobile P4 to work. But all Asus dont support voltages lower than stock.

In general Aopen, Gigabyte, and possibly Abit support good undervolt options. Asus, Msi, Epox, Intel are bad undervolters.

Shame about having to cut a pin just to get memory to work a 1:1. I take it there are no newer BIOS improvements to solve the issue? The Gigabyte's look like a very nice option

Yeah some motherboards just lock most of the options to increase the FSB for ALL 400FSB CPU's, wether they be mobile P4's or ordinary desktop P4's.

Im sure alot of overclockers will know with the old 400FSB CPU's in todays motherboards the bios just prevents them from running at a 1:1 ratio with memory and chipset.
All cutting the pin on the CPU does is make the motherboard think its a 800FSB CPU.

I doubt companies like gigabyte and aopen will change this with their boards, I think its a standard 'safety' feature to limit the overclockability of 400FSB Pentium4's.

Now my friends Asus P4C800-E Deluxe did not have this problem, he had full overclocking options with the bios, hence he did not cut any pins. But he forgot that Asus boards dont undervolt below stock before he bought it.
Hes running his 2.2Ghz C1 stepping P4-m @ 3ghz 1000Fsb 1:1 mem ratio.

Again the pin I cut was BSEL1 I found this pic from a post in ABXZone.com forums

Thanks, very informative! I think I'll stick with a decent Gigabyte motherboard because the voltage control is more important to me than outright speed. Shame we can't have the best of both worlds!

Time to sell my Abit KT7A RAID in order to fund all this! It was fun while it lasted . I got hold of a 1.7 mobile P4 yesterday for £12, but the motherboard and ram may be a bit pricier.

Many thanks for your help!

That's a damn fine tip. Thanks for posting that.