I
t’s September 2003, and AMD is about to swing a
64-bit wrecking ball straight into Intel’s desktop
CPU stronghold. The company’s Athlon XP chips
have already been giving Intel’s Pentium 4 CPUs a run for
their money, but AMD’s new K8 chips are about to change
everything. Not only will they bring 64-bit instructions to the
mainstream desktop for the first time, but they’ll also bring
an integrated memory controller with them.
The first consumer 64-bit processor, the AMD Athlon
64 3200+, was unleashed on the world on 23 September,
2003, with two 130nm product lines launching at once. The
mainstream Athlon 64 design, codenamed Clawhammer
had an integrated single-channel memory controller and
used the Socket 754 motherboard socket, with the very first
3200+ model being clocked at 2GHz.
Then, at the top of pile was the Athlon 64 FX line-up, starting
with the FX-51, which was quite different. Using the same
Sledgehammer core and Socket 940 motherboard socket as
AMD’sOpteronserver-orientatedCPUs(releasedinAprilthe
meyear),theFX-51requiredregisteredmemory,buthad
annelstotransferdatabetweentheRAMand
o registeredDDRDIMMs(orRDIMMs)of identical size, frequency and CAS 2 latency could work in
concert, using a pair of 64-bit data connections to read and
write to two modules at once, boosting memory bandwidth.
Both processor families had 64KB of L1 cache for data and
64KB of L1 cache for instructions, and an exclusive 1MB of
L2 cache. However, some later processors in the series, as
it expanded into more budget-conscious price categories,
would have 512KB of L2 cache. The FX-51 also had an unlocked
multiplier for overclocking, taking firm aim at enthusiasts.
AMD64 CPUs weren’t the first 64-bit processors, of
course. Their many notable precursors include Silicon
Graphics’ 1991 R4000 and its successors, and the RISC-
based DEC Alpha, introduced in 1992, while IBM’s PowerPC
G5 processors were used in Apple’s Power Mac G5
workstations starting in June 2003. Intel’s 64-bit Itanium
server CPUs were also around at this time, although they
were extremely expensive.
But it was the Athlon 64 that pushed the boundaries
of what was expected from a standard x86 desktop PC,
because it not only worked perfectly with 32-bit operating
systems and applications, but also outperformed Intel’s rival
32-bitCPUs when running them.Remember this?
Thebest-known advantage of a 64-bit processor is the
tytoaddress more memory than the 4GB maximum
t CPUs, and AMD put a great deal of attention into
ryhandling.
ilecontemporary Intel and previous AMD CPUs had
ona dedicated memory controller in the motherboard
set’s northbridge, AMD64 CPUs introduced an on-CPU
mory controller with a direct link to the RAM. This meant
erewas no front side bus (FSB) – or EV6 bus in AMD’s case- involved in shuttling data between the CPU, northbridge
memory controller hub and RAM.
Having the memory controller on the CPU means that
RAMspeed is a fixed fraction of the CPU speed, rather than
beingpegged directly to the FSB speed. Early Athlon 64
RETRO TECH / ANALYSIS
Athlon 64
K.G. Orphanides looks back at AMD’s K8 years, when Athlon
64 CPUs were smashing Intel’s NetBurst chips into a pulp
o
CPU. This meant o32-
mereli