In February 1967, NEC announced the NEAC-1240—the world's first ultra-small computer using ICs. After the announcement of the NEAC-1201 in 1961, parametron ultra-small computers were outstanding in terms of stability and reliability, but NEC gradually realized their inferiority to transistors in terms of performance, and in 1965 they began development of a high-performance ultra-small machine using ICs (Integrated Circuits) due to the improvement in IC performance. In addition to switching to ICs, the NEAC-1240 was the first computer in this class to use core memory. The performance of the NEAC-1240 was revolutionary for an ultra-small computer at the time. Its calculation speed was more than 200 times higher than the NEAC-1210, and its memory capacity (at 1,600 words) was more than 3 times greater. Two high-capacity magnetic drums could be connected as external memory units, and paper tape speed was also increased. Nevertheless, the JECC rental fee was 140,000 ten per month, and after it went on sale, orders flowed in at a rapid pace (reaching a total of 280 units in the first 10 months). In June 1970, NEC announced the NEAC-1240D, which had advanced features such as a magnetic drum unit and typewriter. Together, these two models shipped a total of about 1,430 units.