Socket A (also known as Socket 462) is a zero insertion force pin grid array (PGA) CPU socket used for AMD processors ranging from the Athlon Thunderbird to the Athlon XP/MP 3200+, and AMD budget processors including the Duron and Sempron. Socket A also supports AMD Geode NX embedded processors (derived from the Mobile Athlon XP). It compliments (and later supersedes) the prior Slot A CPU interface used in some Athlon Thunderbird processors. The front-side bus frequencies supported for the AMD Athlon XP and Sempron are 133 MHz, 166 MHz, and 200 MHz. Socket A supports 32-bit CPUs only.
The socket is a zero insertion force pin grid array type with 462 pins, hence the alternative name Socket 462. About nine pins in the socket are blocked to discourage accidental insertion of Socket 370 CPUs on Socket A motherboards.
Socket A was replaced by Socket 754 and Socket 939 during 2003 and 2004 respectively, except for its use with Geode NX processors.
Initially launched with 100 MHz FSB support in the earliest chipsets it evolved stepwise to faster 200 MHz FSB while maintaining pin compatibility throughout its lifetime. However, clock, timing, BIOS and voltage differences restrict compatibility between older chipsets and later processors.[2]
Socket dimensions are 5.59 cm (5.24 cm without lever) × 6.55 cm or 2.2" (2.06" without lever) × 2.58", slightly bigger than Socket 370 sockets.
Heatsinks were commonly attached directly to the CPU socket, but some motherboards also had 4 holes for fastening bigger heatsinks to the motherboard. Those holes are placed in a rectangle with lateral lengths of 35 mm and 65 mm.
AMD recommends that the mass of a Socket A CPU cooler to not exceed 300 grams (10.6 ounces). Heavier coolers may result in damage to the die when the system is not properly handled.
All Socket A processors (Athlon, Sempron, Duron and Geode NX) have the following mechanical maximum load limits[3] which should not be exceeded during heatsink assembly, shipping conditions, or standard use. They came with a warning that load above those limits may crack the processor die and make it unusable. The limits are included in the table below.
| Location | Dynamic | Static | |
|---|---|---|---|
| Die Surface | 445 N (100 lbf) | 133 N (30 lbf) | |
| Die Edge | 44 N (10 lbf) | 44 N (10 lbf) |
AMD offered official chipsets for the Slot A/Socket A CPUs. These are included in the table below.
| Model | Code name | Released | CPU support | FSB/HT (MHz) | Southbridge | Features / Notes | |
|---|---|---|---|---|---|---|---|
| AMD-750 chipset | AMD-751 | August 1999[4] | 50 (100MT/s) | AMD-756, VIA-VT82C686A | AGP 2×, SDRAM Irongate chipset family; early steppings had issues with AGP 2×; drivers often limited support to AGP 1×; later fixed with "super bypass" memory access adjustment.[5] | ||
| AMD-760 chipset | AMD-761 | Nov 2000 | 66 (133MT/s) | AMD-766, VIA-VT82C686B | AGP 4×, DDR SDRAM |
Third-party chipsets include the nForce, nForce2, and a large number of VIA K-series chipsets.
In practice, third-party chipsets were heavily favoured by motherboard manufacturers. Stability problems and compatibility quirks from these chipsets abounded from manufacturers not following chipset designers' guidelines. This caused long-lasting damage to AMD's reputation, despite AMD having nothing to do with the poorly-realised hardware. A similar incident happened with third-party chipsets for Super Socket 7 CPUs, of which AMD tried to remedy it by putting quality assurance measures for the Athlon, which used Slot A/Socket A CPUs. Despite this, however, the aforementioned problems mentioned above still lingered on for quite a while, even for Athlon CPUs.