Build A PC

A custom PC configuration guide. © 2000,2001,2002,2004 by Jef Poskanzer.

Sockets and Slots and Slotkets, Oh My

There are a bunch of different connectors used by CPUs.

AMD's socket for the Opteron and the Athlon 64-FX.

AMD's socket for the Athlon 64.

mPGA603 / mPGA604
These are Intel's new sockets specifically for the Pentium-IV Xeon. The socket equivalent of Slot-2. The difference between the 603-pin version and the 604-pin version is that Xeons with a 533MHz or 800MHz FSB have the extra pin, therefore they don't fit into boards with the 603-pin socket. The extra pin isn't connected to anything, it's just there to enforce the bus speed difference. The older 603-pin Xeons will fit into the 604-pin sockets and function correctly, at their usual 400MHz bus speed.

Third-generation Pentium IV socket - started showing up in mid-2004.

Second-generation Pentium IV socket.

An update to the FC-PGA socket. Backwards compatible - FC-PGA CPUs can be used in FC-PGA2 sockets. Current info is that FC-PGA2 CPUs have a heat-spreader added, but it is unclear what difference this makes for the socket.

In late 2000 Intel introduced the Pentium IV processor, and it uses a new socket design with 423 pins. This is not compatible with the 370-pin socket used by current Pentium IIIs, nor (of course) with AMD's 453-pin Socket-A.

In mid-2000 AMD introduced the new Duron processor and the redesigned Athlon, with on-chip full speed level-2 cache just like Intel's latest CPUs. At that point they switched from a slot form back to a socket.

With Intel's high-density 0.18 micron process they can now fit the level-2 cache on the main CPU chip, so the Slot-1 daughter board is no longer necessary. The form factor for these new chips is physically the same as the old Socket-370, but the pinouts are somewhat different. Still, you can get an adaptor to run an FC-PGA CPU in a Socket-370 motherboard.

With the Athlon Classic, AMD did the same thing as Intel, putting CPU and level-2 cache on a little daughter board. Their board was not compatible with Intel's though, perhaps for copyright reasons.

Used by Intel's Xeon processors. Similar to Slot-1, but with more memory lines. You can get a very simple adaptor that lets you use a Slot-1 CPU in a Slot-2 motherboard.

Used by later Celerons, and VIA's new M-III CPU.

With the later Pentium IIs and early Celerons, Intel started packaging the main CPU chip plus some separate level-2 cache memory chips on a little daughter board. This is just because it wouldn't all fit onto a single chip. Slot-1 is still used by the Pentium III line.

Not really a different connector, this refers to motherboards which use Socket-7 but run it at 100MHz instead of 66MHz. Still used by AMD's low-end CPUs, the K6-2 and K6-III.

Used by the Pentium Pro and early Pentium IIs. Obsolete.

The socket used by later Pentiums (early Pentiums used Socket-5). Obsolete.

In addition to the simple socket-to-socket and slot-to-slot adaptors mentioned above, there are some socket-to-slot adaptors available, which are generically called slotkets. For instance, ABit sells one (actually the original SlotKET®) which lets you use a Socket-370 CPU in a Slot-1 motherboard.

And if you need to know more, here's another amazingly detailed page all about CPU sockets.

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