Laptop Pin Mod Overclocking Guide
March 01, 2006 at 08:25:00 PM, by Kevin Gilbert
Increase your performance by pin modding your mobile CPU!
Introduction
Looking for additional CPU performance at a low cost? By linking some of the pins located on the back of Intel's Dothan' Pentium M 400MHz FSB CPU, this CPU pin modification (or pin mod' for short) is able to overclock any Intel Pentium M 7x5 CPU by 33% on any Intel 915 chipset-based Sonoma' laptop. Using the "pin mod" method versus traditional PLL clock generator overclocks has the advantage that it is compatible with any Sonoma-based laptop and since PCI frequencies are not altered, there is a greatly reduced chance of instability or other system problems.
The article will first briefly describe the functions of the CPU pins, then explain how the "pin mod" takes advantage of the pins to overclock the CPU. Then this article will walk though the steps of the "pin mod,' before finally examining the overall effect of a 33% increase in CPU frequency.
The primary function of the pins on the bottom of a CPU is to provide a power and ground source for the CPU and to transmit information to & from the CPU, northbridge, and RAM on an Intel-based system. A few of the pins are also dedicated to encode pieces of information. With the pin mod, we take advantage of the pins encoding information to overclock the CPU. Remember that since Intel uses a quad-pumped front-side bus (FSB), the true FSB clock on Pentium M systems is either 100 MHz or 133 MHz; the quad-pumped bus yields a clock rate that is effectively 400MHz or 533MHz, respectively. To avoid confusion, this article will use the true FSB values of 100/133MHz to describe the CPUs
When examining the Intel Pentium M Processor with 2-MB L2 Cache and 533-MHz Front Side Bus Datasheet, we come across a little gem of information. Essentially, the table below describes the pins that tell the motherboard whether this CPU is a 100 MHz or 133 MHZ FSB part. Since CPU frequency is determined by multiplying the true front-side bus value (100MHz in our case) by the "CPU multiplier" (18x in our case), we can overclock the CPU by increasing either the FSB or the CPU multiplier. However, since the CPU multiplier can not be changed, FSB overclocking is the only option we have here. Examining this table, we see that if we can change BSEL[0] to Low (Low refers to the standard lower voltage value, which indicates a zero or off status for the pin), then we can overclock the 100 MHz FSB CPU by an amazing 33%. With a bit of knowledge in simple electrical properties, we know that we can force BSEL[0] to L, or low, by connecting that pin to ground. Since there are an abundance of ground pins nearby, this shouldn't be too difficult. To perform the connection, we will use a thin piece of metal wire, preferably copper.
This modification only works with a 100 MHz FSB CPU and the Sonoma chipset, which supports 133 MHz CPUs. The reason is that the older 855-series chipsets do not support a 133MHz FSB, thus not having the pin detection for it, and a 133MHz FSB CPU is already running at the higher FSB.
The following table lists which CPUs can be overclocked through this method, and what the resulting CPU frequency will be. The safest bet would be to modify the 715 or the 725. Modifying the 735 or 745 is also possible, but increased voltage will most likely be necessary. A modified 755 or 765 will most likely be unstable, even with increased voltage; thus we do not recommend attempting to use these CPUs.
The reason that the higher clocked CPUs like the 745 through 755 have a lower success rate is simple: they're most likely at or near their clock speed limit. When Intel labels chips for different speeds, it goes through a process known as speed binning. They take each chip and test it for its maximum stable clock at the default voltage. Not all chips are created equal, so the fewer quantity (thus more expensive) chips which can sustain high clocks like 1.8GHz and up are selected for the higher end models. Once Intel has enough of the high end chips, it takes the rest and bins them as lower speed. So while that 1.6GHz 725 CPU may only be set at 1.6GHz, it might have been an extra chip which can do 2.0GHz or even higher. Because of this, keep in mind that there is no 100% success rate with this. Some users even with the 725 CPU have had no luck with this 33% overclock; thus, as always, you bear a risk of not achieving your desired overclock.
CPU | Initial Frequency | Final Frequency |
715 | 1.5 GHz | 2.0 GHz |
725 | 1.6 GHz | 2.13 GHz |
735 | 1.7 GHz | 2.26 GHz |
745 | 1.8 GHz | 2.40 GHz |
755 | 2.0 GHz | 2.66 GHz |
765 | 2.1 GHz | 2.80 GHz |
Examining the document further, we find this table describing how CPU voltage is encoded by the pins VID[0] to VID[5]. Since raising voltage increases stability (while also increasing heat and power consumption), this chart will come in handy when overclocking, should the overclock prove to be unstable. If voltage modifications are needed, we can increase voltage by connecting any of the VID pins from 0 to 4 to VCC, the ground pin. Connecting VID[0] to ground results in a small increase in voltage, while connecting VID[4] results in a huge increase in voltage. I suggest connecting VID[0] when modifying a Pentium M 735 and connecting VID[2] when modifying a Pentium M 745. Should you choose to work with a 755 (Which we do not recommend), you will want to connect VID[3] to ground.
Now that we know what needs to be done, let us examine the following diagram. This diagram provides the name of every pin on the CPU. To perform the mod, we connect the pin BSEL[0] to a nearby VSS (ground) pin. All the VSS pins are shown in black on this diagram. To increase voltage, we connect the corresponding VID pin to a nearby VSS pin. In the diagram, the BSEL[0] pin is highlighted in red, while all the VID pins are highlighted in blue.
However, as you may have noticed, the pins are all narrowly spaced apart. It is much easier to connect the pin sockets on the motherboard itself, which is what we will be doing.
With the necessary background information in place, we can begin the modification.
{PAGE_BREAK}MaterialsBefore performing the pin modification, one should assemble the following materials:
- Intel Sonoma-based laptop
- Intel Pentium M 100 MHz FSB
- Screwdriver(s), for disassembling laptop
- Tweezers, for manipulating wires
- Thin wire, for connecting the pins. The copper strands found in typical electrical wire work well.
- High quality thermal paste, such as Arctic Silver 5 or Shin Etzu, for increasing cooling efficiency (optional).
- CPU-Z for testing clock frequency
- Prime95 for stressing CPU
For this project,we used lab-quality gold wire for connecting the pins. However, standard copper strands work just as well.
To perform the modification, you'll need to first take your laptop apart. This procedure is different for every laptop model. Depending on the company, this may or may not void your warranty. Some companies check for tampering by placing "void if removed" stickers on key areas, covering screw holes. Our victim of choice, the Dell Precision M70, escaped with its warranty intact.
After taking the laptop apart, remove the CPU heatsink and then finally the CPU. The socket should look like this:
Each one of the holes corresponds to a pin on the CPU. Bear in mind that the previous socket diagram is not oriented in the same direction as this picture. Below is the socket diagram oriented in the same direction as that of the socket in the picture.
Next, carefully bend a short (about 0.5cm) piece of wire into the shape of a "u", so that the wire is able to go from the BSEL[0] pin socket to the adjacent VSS pin socket. Insert the wire with one end in the BSEL[0] pin socket and the other end in the VSS pin socket.
If you wish to increase CPU voltage as well, do the same for the VID pin socket of choice and an adjacent VSS pin socket.
Reinsert the CPU, reapply the thermal paste per manufacturer instructions, screw on the heatsink, and screw your laptop back together.
Now, boot into Windows and run the Prime95 stress test. Go to Options -> Torture Test, and select In-place large FFTs.' This will cause your CPU usage to jump to 100%. When Prime95 is working, the icon will turn red. If the icon turns back to yellow, you know that Prime95 failed, which signifies that your system is unstable. Prime95 will not quit on its own; the only time in which the test will stop is if you manually go to Test -> Stop, or if your system is unstable.
Now, run CPU-Z. Congratulations, your CPU is now running 33% faster than normal! Bear in mind that CPU-Z will not display the correct voltage if you performed a voltage modification.
That's right baby! 2.4GHz!
Should Prime95 display a failure message in less than 30 minutes or so, you will need to increase voltage by taking your laptop apart again and connecting a higher VID[x] pin to VSS.
{PAGE_BREAK}TestingAs with any project requiring any significant amount of time and money, it is necessary to consider if the end result is actually worth the effort.
While certainly performance will improve, one will definitely not be able to see much performance improvement when running lightweight applications like web browsing or word processing.
With all this aside, let's consider a few CPU intensive benchmarks across the entire range of Pentium M processors, including the overclocked 2.4 GHz version made by pin-modding a Pentium M 745.
SuperPIcalculates the irrational number Pi up to a certain number of digits. We calculated Pi up to 1 million digits. The program measures the total calculation time in seconds, meaning a lower number is better.
Cinebench 9.5 is the free benchmarking tool for Windows and Mac OS based on the powerful 3D software CINEMA 4D. The tool is set to deliver accurate benchmarks by testing not only a computer's raw processing speed but also all other areas that affect system performance such as OpenGL, multithreading, multiprocessors and Intel's new HT Technology. The benchmark renders a scene and records the amount of time it takes to run. From that information, a score is given. A higher score is better.
Cypher, a part of the Sciencemark 2.0 scientific benchmark suite, tests four different forms of encryption algorithms, AES 128/256 bit and RSA 512/1024 bit. Total runtime is measured in seconds, meaning a lower number is better.
| Frequency | SuperPi 1M | Cinebench 9.5 | ScienceMark 2.0 Cypher |
| 2.40 GHz | 33 sec | 339 CB-CPU | 13.6 sec |
| 2.26 GHz | 35 sec | 318 CB-CPU | 14.4 sec |
| 2.13 GHz | 36 sec | 300 CB-CPU | 15.2 sec |
| 2.0 GHz | 38 sec | 282 CB-CPU | 15.2 sec |
| 1.86 GHz | 39 sec | 263 CB-CPU | 16.2 sec |
| 1.73 GHz | 42 sec | 244 CB-CPU | 17.3 sec |
| 1.60 GHz | 45 sec | 226 CB-CPU | 20.0 sec |
The CPU "pin mod" is a relatively fast and straightforward laptop modification capable of high performance gains for minimal cost. Since Sonoma-based laptops come with 133 MHz FSB Pentium Ms instead of the needed 100 MHz FSB Pentium M, the real problem is finding one for sale online. Online auctions such as Ebay, as well as online enthusiast forums are a great place to start the search for a 100 MHz FSB Pentium M. Once this part is found, prices should be fairly low, especially since only the low-end 100 MHz FSB Pentium M CPUs are most useful for performing the modification. It is very possible to sell your original 133 MHz FSB Pentium M for the same price that you paid for the 100 MHZ FSB version, which adds to the value of this modification.
Even if one does not run CPU-intensive programs frequently, performing this modification is still a great way to introduce yourself to the world of laptop modding.
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Comments
notebook reviews at 04:28, July 06, 2010
Thank god it's easy to install, But i was confused after buying this. I installed it after 6 days when i buy. Thanks to your blog helped me or else i don't know till how many days i would have this one un installed.
Pavlo Fabri at 13:36, January 12, 2010
I was able to overclock without any hardware mods, using ClockGen, with PLL set to ICS 950405. My motherboard is the Onyx2 ( i have a desktop with the pentium m! outrageous isnt it?)