Getting more RAM, part 1

In 1955, C. Northcote Parkinson proclaimed an adage, which is now stated: work expands to fill the time available for its completion. Parkinson ’s Law has many corollaries. I have recently run into one: computer memory usage expands to fill the available RAM. Two years ago, I upgraded my computer hardware to gain more memory, going from 4 GB to 16 GB of RAM. At first, sixteen gigs seemed like a vast expanse of storage, but as I started doing more composites, it began to feel constricting. I am now doing 3000×20000 pixel images with as many as forty layers, and I need more memory.

My current image editing machine, a Dell T3400, is not expandable beyond 16 GB, so I need a new computer. I would like to go to 48 GB. I would also like one six-core processor. There are two reasons for not wanting a dual-processor machine, Photoshop doesn’t use more than two or three cores well for most operations, and the ac power required to supply a second processor can be more than 150 watts. I want the machine to fit under my desk, which limits the height to 24 inches. I want to be able to have at least three internal disk drives. I want a solid state boot disk. I want a quiet machine. I want the machine to be easy to work on. I’d like on-site service in case I don’t feel like fixing the machine myself. I am operating system agnostic, since the new computer will be simply a vehicle for running Photoshop and Lightroom.

I started my search by picking four vendors: Apple, Dell, hp, and Lenovo, the largest and the most well-known workstation manufacturers. A little research produced a surprise. Apple is not always the highest-cost alternative. In fact, because all the manufacturers charge exorbitantly for RAM, disks, and high-performance processors, it makes sense to purchase basic configurations and upgrade them yourself. This means that the difference in base machine cost is not worth worrying about. Power supply efficiency is similar across the machines of interest, running at 85% except for one high power hp supply which gets 89%. Workstations are smaller than they used to be, and all the computers I looked at will fit under my desk.

I ran into a memory expandability problem with the Mac Pro, the Lenovo C20, and the hp Z600. None of these computers will allow 48 GB of RAM (assuming 8 GB DIMMs) with a single processor. The Mac Pro stops at 32 GB, only 24 GB of which is fast because of the way that the Westmere/Nehalem Xeon memory architecture works: there are three memory busses, called channels, and maximum interleaving occurs with the same number of DIMMs on each channel. The C20 and Z600 have more sensible DIMM counts (one per channel), with the same result: if you want more than 24 GB, you need to add another processor.

I threw out the Dell T5500 because it only has two internal disk bays. That left me with the Dell T7500, the Lenovo S20 and D20, and the hp Z800.