Machines with serial main storage devices such as acoustic or magnetostrictive delay lines and rotating magnetic devices were usually serial computers.
There are modern variants of the serial computer available as a soft microprocessor[2] which can serve niche purposes where the size of the CPU is the main constraint.
The first computer that was not serial and used a parallel bus was the Whirlwind in 1951.
1-bit computer instructions operate on data consisting of single bits, whereas a serial computer can operate on N-bit data widths, but does so a single bit at a time.
Most of the early massive parallel processing machines were built out of individual serial processors, including: