Hardware Reference
In-Depth Information
Although the Slot A cartridge looks a lot like the Intel Slot 1, and the Socket A looks like
Intel'sSocket370,thepinoutsarecompletelydifferentandtheAMDchipsdonotworkin
the same motherboards as the Intel chips. This was by design because AMD was looking
for ways to improve its chip architecture and distance itself from Intel. Special blocked
pins in either socket or slot design prevent accidentally installing the chip in the wrong
orientation or wrong slot. Socket A versions of the Athlon closely resemble the Duron.
The Athlon was manufactured in speeds from 500MHz up to 1.4GHz and uses a 200MHz
or266MHzprocessor(frontside)buscalledtheEV6toconnecttothemotherboardNorth
Bridge chip as well as other processors. Licensed from Digital Equipment, the EV6 bus is
the same as that used for the Alpha 21264 processor, later owned by Compaq. The EV6
bus uses a clock speed of 100MHz or 133MHz but double-clocks the data, transferring
data twice per cycle, for a cycling speed of 200MHz or 266MHz. Because the bus is 8
bytes(64bits)wide,thisresultsinathroughputof8bytestimes200MHz/266MHz,which
amountsto1.6GBpsor2.1GBps.ThisbusisidealforsupportingPC1600orPC2100DDR
memory,whichalsorunsatthosespeeds.TheAMDbusdesigneliminatesapotentialbot-
tleneck between the chipset and processor and enables more efficient transfers compared
to other processors. The use of the EV6 bus is one of the primary reasons the Athlon and
Duron (covered later) chips perform so well.
The Athlon has a large 128KB of L1 cache on the processor die and one-half, two-fifths,
or one-third core speed 512KB L2 cache in the cartridge in the older versions; 256KB of
full-corespeedcacheinSocketAAthlonandmostAthlonXPmodels;and512KBoffull-
