IBM OS/390

By Moshe Bar

August 1, 2000

I asked IBM for a review copy of OS/390. It took a while to explain what my intention was. After all, nobody ever goes out and buys an OS like OS/390 costing millions of dollars in license fees based on a review by Moshe Bar. But it helps to know the right people. In my case, things were facilitated by a friend who is an IBM executive high up in the internal food chain.

IBM sent me OS/390 file images pre-generated for all major subsystems, such as DB2, CICS, and more. It was a snap to IPL OS/390 and start playing.

It really all works, with very acceptable speed. And it never once crashed or failed during a month of stress testing with remote terminals connecting from the Net.

Alas, I had forgotten too much of MVS, TSO, and CICS to do anything meaningful.

On the Hercules page, I found the name of Mike Ross. Mike is a historic computer collector. There is an exclusive but growing club of people who go out and buy old mainframe computers and other historically important computers such as DEC's PDP8, 10 and 11 series. Mike Ross has some very old computers in his warehouse and even some working ones at his home in New York City. Mike is also an operating-systems collector, and he was very helpful in the installation and use of the OS/390 on my system. Mike's Web page can be visited at

Let it be said that Hercules is not RAM intensive, but it makes good use of multiple CPUs due to the heavy use of kernel threads it makes internally. A mainframe with 8 Mbytes was already a big one in its day, and so the emulator makes very little use of my Linux server's 1,012-Mbytes of RAM.

Once I had OS/390 and all its subsystems loaded, I went into my archive and searched for an old diskette with a dump of my source files from back in 1981. On the diskette, I found various PL/1 programs to calculate the Eight Queens problem (find all possible positions for eight queens on a chessboard so that no one can beat any other one). There are a number of algorithms for this problem. An obvious choice for an algorithm is the recursive, back-tracking one, which is often used for compiler parsers.

Luckily, there was a copy of the excellent IBM PL/1 Optimizing compiler on the OS/390 system image I got; and presto I was able to compile and test the program. I don't remember how fast said IBM 370/158 MP could calculate the 92 solutions, but on my Hercules emulator it took just under half a second.

Hercules is certainly good enough for light production environments. It is very stable and extremely easy to use and set up. If you are just keeping a mainframe in your data center because of a few last remaining applications, you might want to try Hercules. Contrary to many IBM mainframes, Hercules doesn't need water-cooling to run.

There has been a huge surge in emulator activity in the open source community in recent years. Emulator mania has brought emulators for most game computers, such as GameBoy, Sega, and early Commodore VIC computers. Then, VMWare announced an Intel x386 emulator capable of loading standard Intel OSes under it.

Hercules, certainly has a real commercial purpose.

Copyright 2000