Modifying An Asus A7V Motherboard For Duron-Overclocking
Редакция THG,  8 августа 2000


Revealed: Unlocking AMD's Overclocking Protection

Intro

This task is a challenge especially for users who are fond of overclocking. What has happened so far? AMD locks its new TBird Athlons and Duron processors in SocketA packaging (CPGA) with a fixed multiplier to prevent CPU operation beyond the defined specification. The manufacturer uses the same method as competitor Intel for the Celeron and Pentium processors. However, in practice there are significant differences: While Intel equips its CPUs with special SRAM registers (multiplier lock) to prevent tampering with the multiplier, AMD supplies all its processors with small integrated contact bridges (L1 to L7) on the topside of the case. The actual coding of multiplier and core voltage is done with a CO2 laser by cutting the contacts depending on the processor type.

In the article Overclocking AMD's Thunderbird and Duron Processor, we already discovered the combinations for the contact bridges. But we had a CPU without multiplier lock for this test and thus were able to overclock the Duron 700 on the Asus A7V without any problems. Back then the Asus A7V was an exception among the available boards with SocketA (a.k.a. Socket462) and VIA KT133 chipset: An additional DIP switch on the board allowed changing the multiplier. This enabled us to easily overclock CPUs without fixed multiplier. Today the situation is slightly different though: AMD does not ship processors without a fixed multiplier anymore, and the revised Asus A7V has no DIP switch for the multiplier.

Asus A7V
This board makes it possible: The Asus A7V is an excellent basis for successful overclocking. We modified this board step by step to bypass AMD's multiplier lock.

For this reason we developed modification instructions that enable circumventing the fixed multiplier of any new Duron or Thunderbird processor on an Asus A7V. The great thing about this handy work: The necessary components only cost about 3 US Dollars, and the expected performance increase is about 30 to 35 percent! For example: Our Duron 700 runs completely stable at 900 MHz!

Modification Instructions: Asus A7V as Overclocking Basis

Before we go into the details of this modification we must establish the prerequisites. In principle it works with every Asus A7V that does not have an additional DIP switch for the multiplier settings. This is easy to determine by checking whether there is no second DIP switch next to the one for the Front Side Bus clock. But the board layout already contains the connectors for the additional DIP switch.

Regarding the CPU (Duron or Thunderbird) there is only one thing to verify: all contacts of the L1 bridges must be closed. According to our experience the L1 bridges are closed on most of the currently shipped processors. If this is not the case, however, the contacts must be closed carefully using a conductive pen. When closing the contacts manually, it is important to make sure not to create any connection between the individual bridges.

The picture below shows a Duron that was manufactured with closed L1 contact bridges.

AMD Duron Kontaktbrücken
Important prerequisite for successful overclocking: All bridges of the L1 contacts must be closed.

We must also point out here that despite contrary reports, the successful unblocking of the multiplier is not trivial by any means. Besides the necessary components, the following modification requires a certain skill with the soldering iron. The changes on the motherboard must be made carefully and with precision, otherwise the board might not work anymore due to wrong connections (short circuits).

Modifications for Less Than 3 Dollars

Three components must be added to the Asus A7V to enable the multiplier settings according to the adjustments printed on the circuit board. A listing of the necessary components is shown in the table below.

Component Name Type Position on the board Price
DIP Switch 6 DIP adjacent to first DIP $1.50
Logic IC (SMD) 74F125 U42 $0.80
SMD Resistor 8-pin, 100 Ohm R16 $0.70

These components must be purchased for the modification of the Asus A7V. The financial expense is about 3 dollars.

The next picture shows what the individual components look like. The DIP block is available from most mail-order stores for electronic components. Getting your hands on the two SMD components might be a little more difficult: they should be available in stores specializing in electronics that usually offer a large variety of SMD components.

Components
These are the individual components: 1 - DIP block with 6 switches, 2 - Logic-IC and 3 - multiple resistor.

In Depth: Modifying the Asus A7V

First the DIP switch is soldered next to the switch that is installed already. Make sure that the necessary contacts are arranged in the first layer of the circuit board. The lowest fourth layer only is only for attaching the DIP-switch and does not function as a contact.

DIP switch location

The DIP switch for the multiplier adjustment is inserted in this free spot.

DIP switch

This picture shows the added DIP block. Now everything is ready for the coding of the multiplier.

Soldering connections

Precision work is an absolute must for successful overclocking. Important: Cold-soldering connections should definitely be avoided.

Tricky: Installation of the SMD Components

Now both the SMD components are added near the CPU socket. Apart from a soldering iron this work also requires a deflux pump and the appropriate flux. The picture below shows where to place both the components.

SMD components location
The SMD resistor (8 pins, 100 Ohms) must be inserted in position R16. The Logic-IC is placed in U42.


SMD components
This is how the completely equipped circuit board (Asus A7V) looks like. Adding the R16 resistor requires working very carefully.

The installation of the very small resistor R16 (see picture further above) requires a miniature soldering iron and quite a steady hand. Otherwise it is very easy to accidentally solder the contacts that are very close together. We used a 150-ohm resistor on our test board because the appropriate part (with 100 ohms) was not available. In this case the CPU core voltage should be increased to 1.8 Volts, however, to guarantee stable operation. Installing the Logic-IC (74F125) was no problem at all: The task is accomplished quite easily with tweezers.

In principle the board is ready for operation once all the components are in place. But first the DIP settings must be adjusted. The table below lists all the multiplier variants for AMD's Duron and Thunderbird.

DIP Switch Settings

Multiplier DIP 1 DIP 2 DIP 3 DIP 4 DIP 5 DIP 6
5 on on off on on on
5.5 off on off on on on
6 on off off on on on
6.5 off off off on on on
7 on on on off on on
7.5 off on on off on on
8 on off on off on on
8.5 off off on off on on
9 on on off off on on
9.5 off on off off on on
10 on off off off on on
10.5 off off off off on on
11 on on on on on on
11.5 off on on on on on
12 on off on on on on
12.5 off off on on on on

This table lists all possible variants of the multipliers for AMD Duron and Thunderbird. Even though all CPUs possess a fixed multiplier it can be changed with the modified Asus A7V.


ASUS A7V Mulitplier table

Both the DIP switches "5" and "6" must be set to "on" in all adjustments because they are responsible for unblocking the multiplier lock. In our test we used a locked AMD Duron 700 and increased the clock frequency step by step. The Front Side Bus remained unchanged at 100 MHz. The AMD Duron can be operated with the multiplier setting 9 without any problems resulting in a clock frequency of 900 MHz.

Resume: Money Saved - Significant Performance Increase

WCPUID
The WCPUID tools demonstrates the successful change of the multiplier: The multiplier of the Duron 700 was set from "7" to "9". Because the tool takes into account AMD's DDR technology, it displays only half the value for the FSB clock rate and the multiplier.

To sum it up: This modification of the Asus A7V bypasses the multiplier lock in all AMD processors. Therefore it allows getting a significantly higher performance from a more affordable processor without overclocking the Front Side Bus. The example of our Duron 700 running at 900 MHz (multiplier increased from 7 to 9) shows how much the performance of AMD's Duron and Thunderbird processors can be increased. On top of that the user saves a lot of money, and the Duron 900 (to relate to our example) is not even available on the market yet. Regarding the modifications on the motherboard we want to point out the following: The necessary components cost less than 3 Dollars. You will need some soldering skill to do the intricate soldering correctly. Otherwise the motherboard could be destroyed, while also losing the warranty for it.

Last but not least: AMDs multiplier protection is cracked. Intel's solution with the integrated SRAM registers on the CPU core remains a challenge. Still, while it is hardly possible to overclock any of the AMD processors by increasing the Front Side Bus clock, this method is quite feasible for Intel's Celeron and many Pentium III CPUs.

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