A 1977 Commodore PET with just 8 KB of RAM is a tight fit for anything beyond its earliest software. In a new 17-minute video published on 12 October, Commodore History revisits a period solution: a Compu/Think ExpandaMem board from 1979, populated with 32 vintage-style 4116 DRAM chips.
The interesting part is the hands-on diagnosis, not simply the extra memory. The video walks through how groups of eight 4116 chips provide a byte of data, tests the replacement chips, then installs the expansion in an 8 KB PET 2001 to see what the machine can actually use. It also shows how a failed DRAM can affect the bytes seen by the CPU—a useful reminder that old memory upgrades are repair projects as much as capacity upgrades.
There is a historical twist, too: Commodore History compares the board with an ExpandaMem found in a SuperPET and points to a schematic carrying both a Commodore drawing number and Compu/Think’s name. The video is a look at the practical and commercial afterlife of an early PET expansion, rather than a claim that every 1977 PET can take the same upgrade without checking its hardware.
Watch “Pimping Out My PET: a 1979 ExpandaMem in a 1977 Commodore PET” on YouTube for the chip tests, installation and SuperPET comparison.
