Announced in 1989, this series of office computers from Mitsubishi Electric was equipped with a "GREO" (pronounced "gray-oh") ultra high-speed relational database processor. The GREO processor was commercialized based on the outcome of the research on high-speed sorting technology conducted by Dr. Masaru Kitsuregawa (who at that time was an Assistant Professor of the Institute of Industrial Science, University of Tokyo). This processor was the first to be successfully put into practice in office computers.
GREO was a kind of dedicated hardware to increase the speed of sorting data, and it was comprised of a database processor for executing operations and control relating to database, and a hardware sorter for high-speed sorting under the control of that database processor. In order to continuously supply data between the system bus and hardware sorter, the database processor was equipped with three microprocessors (MC68020) and processed data streams in parallel. The hardware sorter was equipped with 19 originally developed for high-speed sort processing LSI chips and 8 megabytes of local memory (RAM), and sorted 219(approx. 500,000) records at one time using a pipeline merge-sort algorithm. Using these mechanisms, the system sorted a maximum of 2 million records (or a maximum of 64 megabytes) of sort data at a rate of 8 megabytes per second.
GREO dramatically improved system performance, increasing the speed of database processing to 3-50 times its previous level, and reducing the CPU load to 1/10-1/200.
In combination with GREO, Mitsubishi Electric also developed a new fourth generation language called "EDUET" as a language to facilitate the use of relational databases. This was used in ad hoc data analysis tasks.
GREO could be installed as an option in various machines of the MELCOM80 GEOC GR Family of 32-bit single-architecture, ranging from the System 10GR which is a high-performance desktop office computer, to the System 100GR which had the performance of a general-purpose small/mid-size computer.