UltraSPARC T2 Plus detailed

Sun will soon be updating it's UltraSPARC line with the T2+, a slight updated to the T2 - also known as Niagara 2.

The original UltraSPARC T2 is a processor aimed at highly threaded workloads since it is capable of up to 8 simultaneous threads running per core. It has eight cores per socket, delivering up to 64 threads per socket at a clockspeed of 1.2 or 1.4GHz. This highly threaded approach is good to hide latency to the main memory and is similar to the one Nvidia uses in their current GPUs - a "SIMT" programming model - which requires thousands of active threads per GPU to achieve a high throughput.
The T2 is highly aimed at Java workloads, especially enterprise applications, where there are frequent pipeline stalls due to memory accesses, a situation where the highly threaded model has very strong arguments.

The new UltraSPARC T2+, codenamed "Victoria Falls", features the following characteristics:

• Added cache coherence to the T2 - it's the most important change.
• Memory control units (MCU) were reduce from 4 to 2.
• The FB-DIMM pins were reused to create a high speed SERDES link between the cores.
• 51.2GB/s of available bandwidth available for the coherence links, which are four.
• The CPU supports up to 8 cores per socket, SMT provides up to 64 threads, 8 per core. The T2+ has the same one FPU per core as the T2.
• No changes at the pipeline level, which was a short one, so no performance loss or improvements from here.

Below are slides from a SUN presentation about the T2+:







There's also a more in-depth presentation available here.