Seagate on Monday outlined a new technology that promised very high storage density. Heat-assisted magnetic recording, or HAMR, would be just the third major rotating hard drive technique in the market and even in its first generation would lead to one terabit per square inch, a 55 percent boost over today's 620 gigabits per inch. While shy on what HAMR entailed, it noted the technique was delivering performance that had previously been thought "impossible."