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Intel Pentium 4 Processor 560 and Alderwood
By CPU-zilla
Category : CPU
Published by Jimmy Tang on Saturday, 19th June, 2004


The New LGA775 Form Factor

The new Alderwood and Grantsdale platforms will herald a new era of socket form factor known as Socket-T or otherwise also known as LGA775. The new CPU socket will come in a different package altogether and it will not be compatible with current Socket-478 motherboards. This is because the new LGA775 CPU will contain as many, as its name implies, 775 pin-outs. Though we use the term pin-outs loosely, there are actually no pins on the CPU at all. This is a new approach to how a CPU is packaged and even mounted on the motherboard. Though news about the new LGA775 socket has leaked out into the Internet many months back, it is only until recently that we had the opportunity to get a closer look at this new packaging technology.

As mentioned earlier, there are no pins on the CPU and it contains gold contact pads known as a Land Grid Array (thus the name LGA). These gold contact pads provide the interface between the mounted CPU die and the CPU socket on the motherboard. The socket itself is quite an innovation by itself as it has been designed with pins that make contact with these pads. It's quite nearly the complete opposite of what we have today, where the CPU pins are normally found on the CPU.

The new LGA775 socket.


You can see the complexity of the socket up-close, judging from the precise arrangements of the pins.

The question that bugs most of us was, why the change? It's not as if it's impossible to build a CPU with as many as one thousand pins, why do we need to change to an LGA form factor? Look at AMD's Opteron processor, they easily managed up to 940 pins and even 754 pins on their Athlon 64 processor. So why is it that Intel see the need to change to the new LGA775 format? Well, the answer to that is not an obvious one. According to Intel, the new LGA775 package is needed because of the need to bring a more robust power and signal delivery to the CPU. This is to enable the CPU to have more performance headroom in the future. In fact, we were told that this LGA775 socket will be here to stay for the next couple of years.

The problem with the new LGA775 socket lies not in the CPU, but the socket itself. Imagine 775 pins arranged in a proper array with great precision. The cost of the socket is high and it's nearly about seven to eight times more than the current Socket-478. Thus, expect these new motherboards to cost more. In addition to that, we were also told that the pins on the socket could damage quite easily. So, if users do not take extra precautions while installing the CPU, they could damage the board in an instant.

Looking past the above mentioned problems, there are still some goodness left in this new form factor. For one, no matter how you drop the LGA775 CPU, it won't damage that easily and there are surely no pins you could break or bend. In addition to that, we were told that the new LGA775 CPUs would cost less than the current Socket-478 counterparts, and this is probably an effort on Intel's part to offset the additional cost of the new socket incurred by the motherboard manufacturers.

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