I searched quite a lot about my problem, found people with similar issues but I couldn't find a solution. I recently bought an HP Z600 to a professional seller on eBay. It is equipped with 2 Xeon X5670 and 24GB 10600R RAM, Windows 10 Pro 64 bits. I bought it to run extensive simulations on R for my PhD. The seller has approximately 100% satisfaction.
Here is my problem: the computer has very LOW performances. For comparison, I ran the same program (not using parallel computing) on my laptop equipped with an i7-5600U and 8GB RAM. On the laptop, it takes about 150 seconds, and 250 seconds on the dual Xeon computer. The CPU never seem to be overworking or anything else, according to the task manager (at most 10% CPU usage, more or less 10% for RAM usage too). I know the Xeon X5670 is not supposed to be a Ferrari (at least according to latest big CPUs), but isn't it a little too much ?
I tried running some programs in parallel. I could see the CPU and RAM usage increasing to around 90-95%. In some cases the RAM usage increased to 100% so I tried an upgrade, changing the 24GB to 64GB 10600R. The upgrade seems successful (I see the 64GB in the BIOS as well as in the task manager), but it's not faster. The Intel Turbo Boost is enabled, I tried enabling/disabling the hyperthreading, but it didn't change anything. The computer is on high performance mode (it was on the standard mode initially but anyway it had no effect to change it). I checked HWMonitor, everything seems fine. The computer in itself runs fine otherwise.
I will be very thankful to anyone who can help me with this, I am quite worried that I might have thrown my money away, and that I might be unable to run my simulations for my PhD.