Explanation: The CR1 instances are part of the memory optimized instances. They offer lowest cost per GB RAM among all the AWS instance families. CR1 instances are part of the new generation of memory optimized instances, which can offer up to 244 GB RAM and run on faster CPUs (Intel Xeon E5-2670 with NUMA support) in comparison to the M2 instances of the same family. They support cluster networking for bandwidth intensive applications. cr1.8xlarge is one of the largest instance types of the CR1 family, which can offer 244 GB RAM.
Reference:
http://aws.amazon.com/ec2/instance-types/