a first environmental chamber and a second environmental chamber, each environmental chamber comprising:

a backplane forming one side of an environmental chamber;

motherboard sockets mounted on a first side of the backplane;

removable module motherboards for insertion into the motherboard sockets;

a plurality of memory-module sockets mounted on each of the removable module motherboards, the plurality of memory module sockets for receiving memory modules for environmental testing in the environmental chamber;

card sockets mounted on a second side of the backplane;

removable pattern-generator cards for insertion into the card sockets;

a pattern generator on each of the removable pattern-generator cards for generating address, data, and control signals to write data to a plurality of memory locations on memory chips on the memory modules inserted into the memory-module sockets on the removable module motherboards;

a first heating unit that receives second return air from the second environmental chamber and generates first heated air that is forced into the first environmental chamber; and

a second heating unit that receives first return air from the first environmental chamber and generates second heated air that is forced into the second environmental chamber;

wherein the first heated air from the first heating unit is forced into the first environmental chamber and flows past the memory modules in the first environmental chamber to heat the memory modules, wherein the first heated air having passed the memory modules in the first environmental chamber becomes the first return air expelled from the first environmental chamber into the second heating unit;

wherein the second heated air from the second heating unit is forced into the second environmental chamber and flows past the memory modules in the second environmental chamber to heat the memory modules, wherein the second heated air having passed the memory modules in the second environmental chamber becomes the second return air expelled from the second environmental chamber into the first heating unit;

wherein air is recycled through the first environmental chamber and the second environmental chamber by the first heating unit and the second heating unit,

whereby memory modules are tested within the first and second environmental chambers by pattern generators on removable pattern-generator cards outside the first and second environmental chambers that are separated by the backplane.