Shuttle AV45GT2 – P4 Overclocking The VIA Way

As most of you may already have heard, many people are overclocking
their P4 Northwoods. Some reach really high speeds. Most use i845D
or SiS645 based Socket 478 mainboards.

You may also have heard from VIA´s
chipsets for the Pentium 4. So far, they haven´t been as popular.

Today, I want to show you the Shuttle
mainboard (thanks to Shuttle
!). It´s a Socket 478 mainboard, which uses the VIA P4X266A
Northbridge and the VIA VT8233A southbridge. It´s one of the first
VIA chipset based Pentium 4 which officially supports 533 MHz Fronstide

Here is a picture showing the mainboard (this is the RAID version of
the Mainboard; I tested the version without RAID):



CPU Support: Socket 478 (Intel Pentium 4 in the 478 pin package)

Northbridge: VIA P4X266A, Southbridge: VIA VT8233A

Memory: 3 x 184 pin DDR SDRAM Socket (max. memory 2 GB unbuffered /
3 GB buffered)

1 x AGP 2.0 slot (supports AGP 1x/2x/4x modes and 1,5V/3,3V electrical

5 x PCI slots

Integrated dual channel UDMA 33/66/100/133 master mode EIDE

8 USB Ports (4 x USB 1.1 and 4x USB 2.0 via VT6202)

Onboard Sound: C-Media 8738 -PCI-6CH/LX (5.1 speaker support)

Hardware Monitoring

CPU 100 / 133MHz FSB setting (FSB step-less setting from 100MHz
to 166MHz with 1 MHz increment)

CPU core voltage setting from +0.025V ~ +0.20V

AGP  voltage setting from +0.05V ~ +0.20V

Chipset voltage setting from +0.1V ~0.2V

Ports:  2 Serial Ports, 1 Parallel Port (SPP, EPP, ECP), 1 PS/2
Keyboard Port, 1 PS/2 Mouse Port, 8 USB Ports, 1x Game / MIDI Port, 1x
Line in, 1x Line out, 1x Mic

Connectors: 1 x ATX power connector, 1 x 4 pin 12V ATX power connector,
1 x 6 pin 5V / 3.3V ATX power connector, 4 x Fan Power connectors, 4 x
UltraDMA/133 Bus Master IDE, 1 x Floppy



The mainboard comes with a USB bracket, which allows you to use 2 USB ports
together with the 2 USB ports on the ATX panel. What´s really nice
is the audio cable, which adds centre and bass channels for the onboard

Something else new to me was a Pentium 4 mainboard using four power connectors:

-ATX connector,


-Auxiliary Power,

-5 1/4″ drive power connector.

You may not need to connect all of them, but it´s
a good add-on which helps to improve stability:


The Test-CPU was my Intel Pentium 1,6A GHz. For the memory, I used 256
MB Samsung CL2 (2 x 128 MB). The graphic card I used was a Geforce 2Pro.
These are the Sandra 2002 Scores, compared to some previously tested mainboards
(see articles at


Pentium 4 1,6A Ghz (RAM @ 133 MHz,  256 MB DDR-RAM CAS2), 

Enmic 4BCX+ (i845D)
Pentium 4 1,6A Ghz (RAM @ 133 MHz,  256 MB DDR-RAM CAS2),

EPoX 4SDA+ (SiS645)
Pentium 4 1,6A Ghz (RAM @ 133 MHz,  256 MB DDR-RAM CAS2), 

Shuttle AV45GT2 (P4X266A)
CPU Benchmark

Dhrystone ALU

Whetstone FPU

3020 MIPS

964/1987 MFLOPS

3019 MIPS

955/1970 MFLOPS

2993 MIPS

957/1968 MFLOPS 
Sandra 2002 CPU Multimedia Benchmark

Integer MMX Enh

Floating Point 3DNow! Enh

6327 it/s

7758 it/s

6309 it/s

7690 it/s

6312 it/s

7698 it/s
Sandra 2002 Memory Benchmark

Int ALU/RAM Bandwith

Float FPU/RAM Bandwith

2032 MB/s

1946 MB/s

2015 MB/s

1954 MB/s

2028 MB/s

1950 MB/s
Super Pi

(1MB data size)

2´18 min

2´21 min

2´17 min

To be fair: The CPU scores of the AV45GT2 are a bit low, because the
CPU Frequency is a something below 1,6 GHz (something around 1,599 GHz
or so), this makes it a bit hard to compare the scores to the other two



As always, overclocking voids your warranty and may destroy or damage parts
of your computer… From the manufactuer side, the board officially supports
400 and 533 MHz quad pumped Frontsidebus. This, together with the stepless
adjustable FSB (setting from 100 until 166 MHz) and the possibility to
adjust the Core Voltage (max. 1,85 Volt), Chipset Voltage (max. 2,65 Volt)
and Ram Voltage (max. 2,65 Volt) already made it possible for me, to overclock
my P4 1,6A to 2,24 GHz (140 MHz FSB; Mem @ 140 MHz CL2). The disturbing
fact, that I couldn´t set the voltage higher than 1,7 Volt (higher
settings wouldn´t let the motherboard post) and the max. Ram Voltage
of 2,65 Volt were holding me back of the highest speed, my CPU can do,
2,4 GHz. I decided to change the first fact by applying two voltage mods
to the mainboard:


Voltage Mods

Disclaimer: These voltage mods are hardcore stuff. This could destroy your
equipment or shorten its life if you do it wrong. This could destroy your equipment or shorten its life even if you do it right, it just may take longer. 🙂

If you can’t lose it, don’t use it. If you decide to try it, you are solely
responsible for anything and everything that might go wrong as a result.

Core Voltage

The Board uses the HIP6301 PWM Buck Controller to regulate the CPU Core
Voltage. I’ve worked with this controller before and it was easy for me to modify it.

I first looked for pin 7 of the controller (the controller is hidden under
the Socket 478 bracket). Then I searched for a good point to solder my
wires to, because I don´t like to solder to the small pins of the
HIP6301 directly. (Some people prefer to use miniclips.)

I found a SMD resistor connected to Pin 7 and soldered
a cable to it. I also found a GND point a few milimeters away from this
point. So I soldered my second wire to this point.

Then I connected a 47 kOhm potentiometer (type doesn´t matter) to these 2 cables. This
potentiometer allowed me to adjust Core voltages as high as 2,03 Volt (I
didn´t want to try higher voltages). See these pictures for more

The HIP6301 Controller with a 47 kOhm potentiometer between Pin 7 and GND

The highest Core Voltage, I tried

Memory Voltage Mod

The Board uses the LM431 from National together with a MOSFET to generate
and regulate the memory voltage. This was also a familiar chip to me.

The LM431 could be compared to something like a adjustable
Zener-Diode. You simply take one pin of the part, decrease it´s
resistance against GND, and that increases the voltage.

Pin 8 is connected to 2 SMD Resistors. I soldered one wire between those 2 SMD
Resistors and one wire to GND. I connected a 2,2 kOhm between these 2 wires
and were able to adjust the memory Voltage (didn´t try further than
3 Volt).

To know what the memory voltage is, measure the voltage between
the marked point (´measure here´) and GND.



With these Voltage Mods, it was possible to increase the FSB as high as
150 MHz (Core Voltage at 1,8 Volt; Memory Voltage at 2,8 Volt; this is an earlier 1,6A), while keeping
the memory at FSB speed and the fastest timings. Here are the Sandra 2002


Pentium 4 2,4 Ghz (RAM @ 150 MHz,  256 MB DDR-RAM CAS2), 

Enmic 4BCX+ / EPOX 4BDA2+ (i845D)
Pentium 4 2,4 Ghz (RAM @ 150 MHz,  256 MB DDR-RAM CAS2), 

Shuttle AV45GT2 (P4X266A)
CPU Benchmark

Dhrystone ALU

Whetstone FPU

4496 MIPS

1428 / 2945 MFLOPS

4497 MIPS

1426 / 2949 MFLOPS
Sandra 2002 CPU Multimedia Benchmark

Integer MMX Enh

Floating Point 3DNow! Enh

9477 it/s

11527 it/s

9486 it/s

11555 it/s

Sandra 2002 Memory Benchmark

Int ALU/RAM Bandwith

Float FPU/RAM Bandwith

2271 MB/s

2179 MB/s

2291 MB/s

2216 MB/s

Super Pi

(1MB data size)

1´36 min

1´35 min

And the winner is: Shuttle! While the i845D is fast, the P4X266A is
a bit faster in this case. However, we´re talking about differences
of about 1%, so it won´t be that hard… I´m a bit sad, that
I couldn´t go higher, but it seems as if 2,4 GHz is the limit of
my Pentium 4 1,6A (also see



Shuttle delivers a fast, rock solid and cheap Socket 478 mainboard
which is also a very good overclocker. Its feature set and price (120 – 150 Euro)
are very compretitive and it seems to be a good
candidate for P4 Northwood overclocking (even at high current loads). However,
the adjustable standard core and memory Voltages could be a bit higher (not everyone
wants to do a voltage mod!). I also wonder, how the first P4X333 based
boards (-> PC333 support) will perform.

Author: Christoph Jadanowski
aka FrankisGER

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