Equipment

The Compaq Personal Server, codenamed ``Skiff,'' is essentially an initial, ``spread-out'' version of the Compaq iPAQ built for research purposes [13]. Powered by a 233MHz StrongARM SA-110 [29,17], the Skiff is computationally similar to the popular Compaq iPAQ handheld (an SA-1110 [18] based device). For wireless networking, we add a five volt Enterasys 802.11b wireless network card (part number CSIBD-AA). The Skiff has 32MB of DRAM, support for the Universal Serial Bus, a RS232 Serial Port, Ethernet, two Cardbus sockets, and a variety of general purpose I/O. The Skiff PCB boasts separate power planes for its CPU, memory and memory controller, and other peripherals allowing each to be measured in isolation (Figure 1). With a Cardbus extender card, one can isolate the power used by a wireless network card as well. A programmable multimeter and sense resistor provide a convenient way to examine energy in a active system with error less than 5% [47].

Figure 1: Simplified Skiff power schematic

The Skiff runs ARM/Linux 2.4.2-rmk1-np1-hh2 with PCMCIA Card Services 3.1.24. The Skiff has only 4MB of non-volatile flash memory to contain a file system, so the root filesystem is mounted via NFS using the wired ethernet port. For benchmarks which require file system access, the executable and input dataset is brought into RAM before timing begins. This is verified by observing the cessation of traffic on the network once the program completes loading. I/O is conducted in memory using a modified SPEC harness [42] to avoid the large cost of accessing the network filesystem.