Wow, I can't believe some people aren't excited about this.
The 4.2GB/sec of memory bandwidth might not mean as much if you're not using the integrated MX since the FSB bandwidth is unchanged (not that the Athlon really needs massive amounts of memory bandwidth), but it makes sense considering the structure of the two controllers:
FSB: 2.1 GB/sec
AGP: 1.06 GB/sec
Hypertransport: .8 GB/sec
= ~4 GB/sec of memory bandwidth that could potentially be used by the "northbridge"...which fits nicely with the 4.2GB/sec of available memory bandwidth. It might be overkill now (I doubt any game or video card uses the full bandwidth of AGP4X, and the IDE/NIC/sound in the southbridge probably won't use too much of the Hypertransport bandwidth), but it's nice to know that the bandwidth is there for the future.
The most impressive thing is the speculative hardware prefetch on the northbridge. It could help a lot with performance...check out
this graph. With all the iterations of DDR chipsets for the Athlon (ALi, AMD 760, Via KT266, Sis 735), it's obvious that despite the identical memory bandwidth, the DRAM controller makes a big impact on performance. With the crossbar memory controller and speculative hardware prefetch, it should be a pretty impressive chipset even for those who aren't using the integrated MX.
In the end, this is the first consumer product:
- with hardware prefetch on the northbridge
- with hardware Dolby Digital encoding
- to use AMD's Hypertransport I/O bus