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.
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.
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).