The first thing worth testing on a new system is the speed of its memory, because if this is slow, both the CPU and disks will suffer accordingly. You might wonder why this is so important. It's because database work is intensive in both these areas. PostgreSQL works with database data in 8 KB pages, and it's constantly shuffling those around to system memory as needed to satisfy queries; looking through those pages for the specific rows needed is CPU-intensive. Even on benchmarks that focus on disk-heavy work, the speed of the underlying memory can have a surprisingly high impact on results.
CPU and memory benchmarking
Memtest86+
One of the most valuable tools in the PC hardware technician's bag is Memtest86...