Fwd: AMD x2 chips

[Mark Hahn]

> > the cores on AMD's dual-core chips are most definitely not 
> > independent ICs.
> 
> So you're saying the ALUs, FPUs, L1 cache, L2 cache, etc... logic is
> merged between the two cores?

no, that's obviously not the case - you can see it from the die photos.
the cores are clearly laid out as separate blocks - that doesn't mean
they're separate ICs, by any normal definition.  for instance, the cores
certainly don't have a pad ring and IO drivers, just to connect to the 
SRQ (another on-die block within the same IC.)

> I'm talking a self-contained integrated circuit that operates on its
> own (short of any power/pin-out).  From my understanding, there's not
> change in what each core is externally, at least logically (and
> fundamentally electrically) from independent dies.

normally, this is simply called a block.  most large ICs have lots of 
blocks - most caches are multiple blocks, for instance.  that doesn't 
mean that the cache can sanely be called multiple ICs.

> > the opposite is true: Intel's DC chips are much closer to being
> > separate ICs, since they're attached with even less bridging
> > (present two bus loads, for instance).
> 
> Huh?  How does interconnect two "front side busses" to a single
> memory controller hub (MCH) without bridging them _before_?

at least the initial Intel DC implementation literally had 
the FSB extended on-die to two electrically independent cores.
since they didn't have a "real" internal bus arbiter, the chip
actually presented 2 bus-loads to the system FSB.

> > so they're going to invent a whole new HT addressing scheme
> > just so they can do glueless HT within the chip?
> 
> No, quite the opposite!  I'm saying the addressing scheme is the
> _exact_same_.  I'm not following your logic at all here.

but you don't seem to be getting the fact that the current HT 
has an 8-node limit.  since you can already buy an 8-socket,
16-core machine (without any sort of HT switching or bridging),
it's clear that each DC socket acts as a single HT node.  it simply
can't somehow have additional HT address range on-chip.

that's the topic: AMD's diagrams and Bill's message point out that 
within a single AMD DC chip, the memory, HT ports and core(s) are 
connected by a non-HT xbar.  the cores are not separately HT-addressable
and neither is the dram interface.