Version 4.5 dates back to 1994. It corresponds to a suffix letter of M on the part number (IC693CPU311M). The highest version for which I have a datasheet is 8.40 dating to December 2003. This corresponds IC693CPU311AD or IC693CPU311AE. The publication number of the datasheet is GFK-0702AC
You can get an upgrade chip from your local distributor for around $100. The part number is 44A731233