Bulldozer (below) packs two integer execution pipelines and one shared floating point unit in a core than can retire four instructions in a clock cycle. AMD claims it will be able to hit higher frequencies than its current cores now shipping at up to 2.3 GHz.
The second integer pipeline requires only 12.5 percent more die area. Performance for the dual-core approach varies with workloads but "we often see an 80 percent boost" compared to 20 percent or less for the simultaneous multithreading technique Intel uses, said Chuck Moore, an AMD corporate fellow and chief technology officer of technology development.
Essentially, AMD is betting that by packing the most critical hardware elements of two cores in a single core design it can outperform Intel which double-tasks one pipeline with its so-called Hyperthreading approach.
However, Intel has yet to reveal the architecture of its 2011 Sandybridge chips which may use a third-generation approach to symmetric multithreading or follow AMD's lead to include more hardware resources. Intel's Sandybridge chips will be its second generation of 32nm processors and the first to integrate graphics and x86 cores on a single die.
Each integer block in Bulldozer has a 16 Kbyte L1 data cache. They share a 64 Kbyte instruction cache. Processors using the cores will implement a wide variety of secondary and tertiary caches, some using no L3 cache at all.
The floating point unit will implement new vector instructions similar to those expected in Intel's next-generation Sandybridge chips which also ship in 2011. The Bulldozer floating point unit includes two 128-bit multiply-accumulate units, the first x86 to have such dedicated hardware, Moore said.
AMD faces big execution risks with Bulldozer given the amount and complexity of new technology in the core, said analyst Brookwood.
"We have invested in methods for workarounds using microcode and other features to turn non-essential optimizations off, so we feel pretty good about getting to market in the windows we are talking about," said Moore.
The first Bulldozer-based processors will fit into AMD's existing 4000 and 6000 series chip set and motherboard platforms, said John Fruehe, director of product marketing for AMD's server group. That should help keep a lid on system testing time, he said.
AMD's Bulldozer marries two integer and one shared floating point units