AMD 64bit CPU differences

Hi

Something I had not picked up on before, but aparently I was wrong when I
thought the Opteron 1-2 way and Athlon 64 FX were identical.

After reading up on the AMD site I was suprised to see that while the Athlon
64 FX has Opteron's dual channel functionality, but it only supports a
single hypertransport path like the standard 64.

Thus I realise this means the FX cannot do multi-processor. Even the 100
series (which is 1-2 way) Opteron had 3 HT links necessary.

Any ideas if this is just something they disable on the core, or are AMD
producing 3 similar but separate versions of the hammer core?

Tim

"Tim Cunnings" wrote in message
...
Any ideas if this is just something they disable on the core, or are AMD
producing 3 similar but separate versions of the hammer core?

My impression is that there are two similar but separate cores, the one in
the regular Athlon 64 (aka Clawhammer), and the one in the Athlon 64FX and
Opteron (aka Sledgehammer). Then within the Sledgehammer core, they enable
or disable certain features by shorting certain bridges after manufacture,
just prior to packaging. The Clawhammer is a single-channel DDR chip,
whereas the Sledgehammer is the dual-channel DDR chip.

Yousuf Khan

On Fri, 26 Sep 2003 15:42:28 GMT, "Yousuf Khan"
wrote:
"Tim Cunnings" wrote in message
...
Any ideas if this is just something they disable on the core, or are AMD
producing 3 similar but separate versions of the hammer core?

My impression is that there are two similar but separate cores, the one in
the regular Athlon 64 (aka Clawhammer), and the one in the Athlon 64FX and
Opteron (aka Sledgehammer).

Nope, only one core. Take a look at the transistor count and die size
of the chips, all are identical. It's just a matter of what is
enabled or disabled that determines whether it's an Opteron 8xx, 2xx,
1xx, an Athlon64 or an Athlon64 FX. All use the same basic die.

FWIW the test versions of the AthlonFX 51 actually had all three of
their hypertransport links active, though apparently this will change
in the very near future if it hasn't already for retail chips.

One thing I'm curious about though. The Opterons all have 3
hypertransport links, however the 1xx series is for uniprocessor
machines only, the 2xx are for dual processor setups and the 8xx and
for 4 and 8-way setups. Does AMD actually enforce this somehow? ie
do the 2xx chips have 3 HT links, but only 1 of them will allow
cache-coherent hypertransport (required for connecting to another
processor)? Or is it just a matter of testing, ie an Opteron 1xx
series chip COULD work in a 4 or 8-way SMP setup, but it just hasn't
been tested and verified as such?

-------------
Tony Hill
hilla underscore 20 at yahoo dot ca

"Tony Hill" wrote in message
.com...
My impression is that there are two similar but separate cores, the one
in
the regular Athlon 64 (aka Clawhammer), and the one in the Athlon 64FX
and
Opteron (aka Sledgehammer).

Nope, only one core. Take a look at the transistor count and die size
of the chips, all are identical. It's just a matter of what is
enabled or disabled that determines whether it's an Opteron 8xx, 2xx,
1xx, an Athlon64 or an Athlon64 FX. All use the same basic die.

Well, depends on what we define as the core. The Clawhammers are
single-channel DDR, whereas the Sledgehammers are dual-channel. Also the
Clawhammers have less L2 cache, don't they?

Yousuf Khan

On Fri, 26 Sep 2003 21:20:21 GMT, "Yousuf Khan"
wrote:
"Tony Hill" wrote in message
t.com...
Nope, only one core. Take a look at the transistor count and die size
of the chips, all are identical. It's just a matter of what is
enabled or disabled that determines whether it's an Opteron 8xx, 2xx,
1xx, an Athlon64 or an Athlon64 FX. All use the same basic die.

Well, depends on what we define as the core. The Clawhammers are
single-channel DDR, whereas the Sledgehammers are dual-channel.

Err, more or less (it's not quite "dual-channel" in the same sense as
nVidia's nForce or RDRAM chipsets, more just a 128-bit wide channel).
However this is simply because on the Clawhammer chips, half of the
width is disabled, not because it doesn't exist.

Also the
Clawhammers have less L2 cache, don't they?

Nope, all have 1MB of L2.

-------------
Tony Hill
hilla underscore 20 at yahoo dot ca