IBM 5150 - Motherboard revisions Home IBM 5150 - Motherboard Revisions There were 2 revisions of the motherboard. IBM differentiated them by the amount of RAM that it was possible to fit on the motherboard: • 16KB-64KB • 64KB-256KB Both were not released simultaneously. The 16KB-64KB motherboard was supplied in early model 5150s, and the 64KB-256KB motherboard was supplied in later model 5150s. Example marking Motherboard RAM Comments 4 banks of 16 KB • Detail on the RAM for this motherboard is here. • Supplied with either the 04/24/81 or 10/19/81 revision of BIOS. • It was common for owners to upgrade the BIOS to the 10/27/82 revision via a BIOS upgrade kit. See note 1. 4 banks of 64 KB • Detail on the RAM for this motherboard is here. • Supplied with the 10/27/82 revision of BIOS. See note 1. Note 1 Due to bugs, the 10/27/82 revision of BIOS requires that all 4 banks of motherboard RAM be populated.