Virtual Varian Machine
Short for Virtual Varian Machine, VVM is one of the most enhanced real-world emulators ever developed to be replaced by obsolete Varian computers. Varian mainframes were the giant computation brains of 70’s. They may be remembered as ultra-expensive computers introduced and used broadly to make things automated.
A Varian mainframe system, as seen below, could run machine code instructions at a clock speed of 4 MHz. This yields to executing several thousand instructions per second. This system made use of 32768 bytes of core memory.
Varian machines couldn’t survive due to the rapid improvement in computation technology. In fact, they were forgotten as more and more powerful computers came to existence. Although they don’t seem to be of any use today, there are some situations where such obsolete computers are still being used.
- Automated test equipment
- Research laboratories
- Control systems
- Industrial automation systems
There are several reasons which justify continuing using an obsolete computer system like Varian. We may not be able simply replace an old mainframe with a modern computer because:
- Tons of assembly code may exist as the system software, re-development of which can take a lot of time.
- Special I/O buses and ports may be used to control equipment, which does not exist in current computer systems.
You may say: “OK, for such situations, we keep our Varian machines working”. Well, for starters, no Varian computer is manufactured any longer, and existing machines are too old to work and must be retired. And to make matters worse, there is not any kind of support for you if you have a Varian machine. What will you do if the core memory of your Varian system stopped working? Can you go and buy a 32768 bytes core memory!?
We suggest the ultimate solution to this problem: VVM, A modern real world emulator of Varian. Although VVM is an enhanced emulator, it is conceptually easy to understand. VVM consists of a VIA C3 processor which emulates instruction set and peripherals of a Varian mainframe. There is an FPGA-based hardware which provides the needed I/O facilities for the VVM to communicate with external equipment which used to be under control of the retired Varian.
Instead of the magnetic tape of Varian, a CD ROM drive is provided. There are some shortcut keys in the front panel for executing the program. Power and I/O ports are accessible from the backside of the case as seen in Figure 3. In the case of Figure 3, we needed 4 I/O ports to communicate with an automated test equipment used to be under control of Varian. An RS-232 serial port is also needed to connect a CRT terminal to VVM. This terminal can be either the Varian CRT or a PC running a terminal program like HyperTerminal. The giant Varian mainframe can be completely replaced with the small box of this advanced system without any change in functionality, even with an improvement in performance. It is because the user does not have to enter a bootstrap or rewind a magnetic tape or wait for a tape to be loaded.
- If you have an old Varian machine which breaks down every day and every hour;
- If there are tons of assembly program codes for your Varian machine which was developed during month and years in 70’s and you do not want to write them again;
- If you wish you could throw your Varian machine away from window once or twice a day;