[ Thanks to Moshe Bar
for this link. ]
“…there is indeed a mainframe emulator capable of IPLing MVS
along with other mainframe OSes, such as VM (an OS capable of
booting other operating systems under it, much like VMware), VSE,
and others. Hercules was developed by Roger Bowler and is now
maintained by Jay Maynard. Both are two very smart developers with
a talent for creating and managing an open-source development
community.”
“The Hercules emulator is very efficient. I dedicated
4-Mbytes of RAM to my virtual mainframe, and checking the Linux
stats I saw that it would use CPU time only when there actually was
real action inside the virtual mainframe. By contrast, VMware
always is up there at 90 percent CPU time, even when the virtual
machines inside it are in the background not doing anything. Of
course, every few milliseconds the virtual machine for both VMware
and Hercules need to wake up to do kernel house-keeping and update
the internal clock, but it seems the Hercules approach to it is far
more wisely designed.”
“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.”