Here is a post that was made on one of the web sites dedicated to John Titor. Regards E. Just a quick note on the 5100. I'm not sure if anyone else has posted anything about the 5100, but this machine was very interesting. In the early 80's, I worked on a slightly upgraded version of the 5100 called the 5110. The 5100/5110 machine executed code intended for IBM mainframes of the time (System 360/370) via a simple processor that emulated the old 360/370 CPU. Languages, such as APL or VS BASIC were programs written in machine language, that were, in turn, interpreted by the CPU in a lower level language called 'Microcode' Microcode allowed IBM to modify or enhance basic machine language instructions at will after the mainframe was delivered to the customer. The concept was 'ship an initial version of the 'machine', but allow upgrades as they were developed without the wholesale replacement of hardware'. To change a basic instruction in microprocessors today usually requires a physical change in the chip, since all instructions are 'hard-wired' into the design of chip. The core design of the 5100 series machine was an emulator of the old IBM 360/370. The CPU of these machines was designed to execute the exact same microcode of the giant mainframes which preceded them. In fact, the 5100 shipped with a ROS (Read Only Storage, rather than ROM, Read Only Memory) card that contained the microcode for the 370 mainframe computer CPU. Any program designed for the 370 could, theoretically, run on the 5100 or 5110. IBM shipped either VS BASIC or VS APL, written in IBM machine language for the 370, on a ROS card in each 5100. No need to recompile, no need to change much, since the little 5100 ran the exact same code as the mainframe. It was not a fast machine, but it worked, and the performance of the old 5100 was good enough to run many of the same applications we had developed on our $10 million twin IBM 370 mainframe installation. APL and VS BASIC apps ran with little or no modification, except for storage device definitions, which were limited to 300KB 8" floppies or 150KB streaming tape cartridges. If 'John Titor' had access to the endless library of old IBM applications written for the 370 (and later 30X0 and 970 series) machines in his time, a 5100 would be a handy, lightweight, SMALL device that could be transported back to his time to run this code. Certainly, no old 370 or subsequent compatible machines from IBM would be available in 2036 to run this code, but a 5100 could do it, and could be moved via his 'time machine'. The basic 5100 machine weighed about 70 pounds and looked like a suitcase. How much software would be available? IBM salesmen used to carry around a little 1.5" thick book of applications written for all possible businesses, from paint manufacturers to hog farming operations that could be installed on any generic IBM 370 compatible mainframe. One can STILL see companies all over the Earth running code that was written many years ago, installed on newer hardware, but running the exact same instructions used in the late 60's, mid-70's. If 'John Titor' and his tales of time travel are a hoax, the inclusion of the 5100 is a remarkable bit of technology that is quite plausible for a society that needs basic data processing, but lacks working hardware and working applications. It's -astonishingly- plausible. I mean no disrespect to those who believe the 'John Titor' story, but only wish to point out the masterful inclusion of something that really could be true. Imagine a 2030's recon group accessing an old IBM branch office, with old archives of business applications stored on old tapes, just waiting for the correct hardware to run on. It would be a virtual gold-mine, with the right hardware... --- Saturday, August 7, 2004, 1:42:33 PM, you wrote: