A CPU Revolution: Sun’s UltraSPARC T1 and T2 Processors

Sun Microsystems’ new UltraSPARC T1 and T2 series of microprocessors have revived Sun’s position as one of the few independent vendors capable of competing with the two large processor companies (Intel and AMD) that currently dominate the processor market. Sun fell behind for a few years when its flagship processor, the UltraSPARC IV series, reached its performance limits. But they have re-entered the competition with their new UltraSPARC processors, completely redesigned from the ground up and capable of new levels of power and flexibility.

The UltraSPARC T1 is the first processor produced by Sun that is multicore and multithreaded. It was first available in 2005 with four to eight CPU cores. Each core is capable of handling four threads at the same time. This means that the processor as a whole is capable of handling between 16, 24 or even 32 threads simultaneously.

The UltraSPARC T1 is the first SPARC-based processor whose multiple cores can be partitioned. Multiple cores can be pooled together to work on a single task or set of tasks, while the remaining cores take care of the rest of the processes and threads. Additionally, UltraSPARC T1 supports Hyper-Privileged execution mode, which means you can partition your cores into up to 32 logical domains (one for each thread on an eight-CPU system). Each of these logical domains could be running its own operating system instance (usually Solaris).

The only downside to the UltraSPARC T1 is that it is only available on uniprocessor systems, which limits its vertical scalability in large enterprise networks. The UltraSPARC T2, released in late 2007, addressed this problem among many other advances and improvements.

The UltraSPARC T2 is, in many ways, an upgraded TI. It contains eight CPU cores, with each core capable of handling eight threads each, for a total of 64 threads being handled simultaneously. This is double the maximum capacity of the T1, which maxed out at 32 concurrent threads. Also like the T1, the T2 supports Hyper-Privileged execution mode. While the T1 could only partition its cores into 32 logical domains, the T2, with more cores available, can partition them into 64 logical domains. Additionally, a bidirectional SMP T2+ system can be partitioned into up to 128 logical domains, each capable of running one Solaris instance.

In addition to doing everything the T1 does (only better), the T2 also had several new features. Among other things, it had increased thread scheduling and instruction prefetching, allowing it to achieve higher single-threaded performance. It also increased the processing speed of each thread from 1.2 for the T1 to 1.4 GHz. While the T1 has a Jbus interface, the T2 has a PCI Express port. The L2 cache on the T2 has been increased to 4 MB (as opposed to 3 MB on the T1). It has four dual-channel FBDIMM memory controllers and eight encryption engines. In early 2008, Sun released a new UltraSPARC T2 Plus processor, which is an SMP-compliant version of the UltraSPARC T2.

Sun MicroSystems’ UltraSPARC T1 and T2 demonstrate that, despite growing competition from Intel and AMD, Sun is still in the processor race, particularly in the high-end server processor market. Sun’s designs continue to be innovative and, as the core partitioning system demonstrates, flexible.