I'm looking to buy a workstation for data processing using MATLAB. I'm considering one of two workstations from DELL. The lower end workstation (3500) has a single processor and 24 GB of memory in 6 DIMMs. The higher end (7500) will only allow me to select 24 GB of memory (in 12 DIMMs) if I select the dual-processor option. The difference between the two seems to be that
The Dell Precision T3500 has a three channel memory bus architecture.
The Dell Precision T7500 has a three channel memory bus architecture per processor
Does this mean that each processor gets 12 GB of memory, and a thread on processor A can't see the same memory as processor B? This seems unlikely, but maybe there is a performance penalty for A to access B's memory?
You're right that the dual-proc machine has 6 memory channels, 3 per processor. This particular architecture is called NUMA and is very well engineered in the system you're talking about - it'll try to keep a thread's memory 'near' to the core it's running on and will be slightly slower if it has to use memory bound to the other processor's memory channels but I wouldn't worry about it at all, every single box I currently use has this type of system and I'm more than happy with performance.