FebruaMaximumPC 2008 02

of the CPUs that AMD is able to produce,

not enough reach 2.4GHz or 2.6GHz to

launch the chips right now—thus the initial

2.2GHz and 2.3GHz CPU rollout.

Q

Will Phenom work in my exist-

ing motherboard?

A

Phenom is designed as a

Socket AM2/Socket AM2+

chip and should, therefore,

drop right into the majority of existing

motherboards, provided the motherboard

maker updates the BIOS—and didn’t screw

up on the board design (see our sidebar on

page 48).

Q

Does Phenom have the same

RAM issues that DDR2 Athlon

64s did?

A

No. AMD corrected the issue

that limited the DDR2 Athlon

64s to whole-num-

ber RAM divisors. This, in essence, would

force DDR2/800 RAM to run at DDR2/766.

Phenom CPUs use a separate clock for the

memory controller, so memory will run at

its intended speed. Consequently, however,

the memory controller no longer runs at the

core’s speed. The memory controller on the

2.6GHz Athlon 64 FX-60 runs at 2.6GHz.

On the 2.6GHz Phenom 9900, the memory

controller runs at 2GHz and notches down

to 1.8GHz for the 2.3GHz Phenom 9600.

It’s not clear if or how this impacts memory

performance; it’s still a good clip faster

than what the memory controller runs at in

competing Intel machines, where that part is

located in the north bridge.

Q

What about online reports that

AMD’s CPU contains a bug?!

A

First, every CPU released,

and probably every piece of

silicon, has bugs. Companies

call them “erratum.” However, there are

bugs and then there are bugs. In the case of

http://www.maximumpc.com (^) | FEB (^08) | MAXIMUMPC 45
AMD’s “true quad core” jams all four cores onto a single 65nm, 285mm^2 die. In addition to other core-efficiency enhancements, AMD
now uses a shared 2MB L3 cache that runs at the same speed as the memory controller, which is currently 1.8GHz or 2GHz.
FPU
L1
CORE 1
L3 L1
CORE 2
L1 L1
MEMORY CONTROLLER
CORE 3
L1
L1
FPU
L1
L1
CORE 4
L2 L2
L2 L2
FPU
DIRECT CONNECT NORTH BRIDGE
DIRECT CONNECT NORTH BRIDGE
L3