Photo: Calxeda Packed in: An HP system will take advantage of Calxeda’s low‑power ARM‑based processors by cramming 288 of them into a single rack unit. There are two giants in the computer processor industry. One is Intel, which builds most of the processors in today’s PCs and servers. The other is ARM Holdings, in Cambridge, England, which thanks to its vast ecosystem of partners has established near-complete dominance of the market for the core logic inside smartphones and tablets.
 But the demand for energy-efficient chips is reshaping the industry. As the PC market flattens, Intel aims to capture a...