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Byte.com: Summer Potpourri: Mainframes And X

Aug 07, 2000, 18:08 (8 Talkback[s])
(Other stories by Moshe Bar)

[ 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."

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