It was pretty simple. I've used and programmed an Alto, back when Stanford had a few around. It was basically a reworked Data General minicomputer in a small rackmount case. 16 bit word oriented, programmable in BCPL or Mesa at the low level, Smalltalk at the higher level. The removable hard disk was the same as a DEC RK05 cartridge disk. The Ethernet interface was very simple, and coax Ethernet was electrically simple. Alan Kay referred to Ethernet as "an Alohanet with a captive ether". The CPU was microcoded, and cycles were stolen from the CPU's microcode engine to run the peripherals. None of this was pushing the state of the art. The CPU hardware was a minimum viable product.

The keyboard, mouse, and display were all new, and nicely engineered. Most of the hardware effort went into those. The keyboard had nice key switches and a massive metal casting. The display was the first good black-on-white display, with a big portrait-format screen. The original mouse wasn't that great.