Introduction to IBM VM/370 Release 6

IBM VM/370 Release 6 was a landmark operating system in the history of enterprise computing and virtualization. Introduced in the late 1970s for IBM System/370 mainframe computers, VM/370 provided a powerful environment in which multiple independent operating systems and user workloads could run simultaneously on a single physical machine.

At its core, VM/370 was built around a sophisticated virtual machine monitor known as CP (Control Program), which created fully isolated "virtual" System/370 computers for each user. Within these virtual machines, users could run CMS (Conversational Monitor System) for interactive computing, or even install and operate complete guest operating systems such as MVS, DOS/VS, or earlier VM releases. This capability made VM/370 one of the earliest practical and widely deployed implementations of full hardware virtualization.

Release 6 represented a mature and highly stable generation of VM/370. It incorporated years of refinement in performance, reliability, and usability, making it well suited for both production workloads and large-scale timesharing environments. Universities, research institutions, and corporate data centers relied on VM/370 Release 6 to support hundreds or even thousands of concurrent users on a single mainframe.

The significance of VM/370 Release 6 extends far beyond its original era. Its architecture established many of the core concepts that still underpin modern virtualization and cloud computing platforms, including isolated virtual machines, dynamic resource sharing, and centralized system management. Technologies such as VMware, Hyper-V, KVM, and today's IBM z/VM can trace key elements of their design lineage directly to VM/370.

VM/370 Release 6 stands as a foundational achievement in computing history—demonstrating that large-scale, secure, and efficient virtualization was not only possible, but practical, decades before it became mainstream.

Running VM/370 Today

The following versions exist:

VM/370 Community Edition

This is the newest version of VM/370. It includes the latest changes from the Sixpack editions plus improved support for the BREXX Interpreter. Download from www.vm370.org.

Robert O'Hara's Six Pack

This is a newer version of the VM/370R6 Public Domain system. It has a more up-to-date GCC with a choice of run-time libraries and extra Editor modifications to allow editing multiple files.

Paul Gorlinsky's 5-Pack System

It has all Andy's fixes plus many enhancements that make it an almost useable system.

Andy Norrie's 4-Pack System

This system is probably the most consistent system available. Andy put a lot of effort into re-working and cross checking the patches but it lacks many of the enhancements of Paul's system.

Bob Abeles's Original 3-Pack System

This is Bob Abeles's original distribution. Unlike the systems above which are distributed as "ready to IPL" DASD, this system is distributed as AWS tapes that need to be restored to 3330 packs.

2000: Bob Abeles's VM/370 R6 Distribution

Bob Abeles released a copy of the IBM VM/370 R6 distribution in its original form, circa 1979 — two "tapes" created with the VM/370 DASD Dump Restore (DDR) program, which need to be restored to 3330 disks. This is exactly how a new IBM customer would have installed VM on their new System/370.

The ".bz2" files are compressed in bzip2 format. The bzip2 and libbzip2 home page has information and source code for the bzip2 utility.

2004: Andy Norrie's VM/370 R6 "4-Pack" System

Andy Norrie built atop Bob Abeles's system. He put a lot of effort into re-working and cross checking the patches.

Download from Jay Maynard's IBM Public Domain Software Collection page http://www.ibiblio.org/jmaynard/.

Paul Gorlinsky's 2006 5-Pack System

In 2006, Paul Gorlinsky released the "5-Pack" VM/370 system. As Dave Wade wrote, "It has all of Andy's fixes, plus many enhancements that make it an almost useable system."

The "5-pack" system is not available from the CBT Tape, but you can download it from Dave Wade's http://www.smrcc.org.uk/members/g4ugm/vm-370/VMDIST.zip website, via the Internet Archive's Wayback Machine.

2009-2021: Bob O'Hara's "SixPack"

In 2009, Bob O'Hara, one of the early IBM VM/370 programmers, announced Release 1.0 of the "SixPack" system. As he wrote, it 'rolls up all of the modifications posted on the H390-VM and Hercules-os380 Yahoo groups since the "5-pack" system was released in 2006.' As with earlier systems, the name comes from the fact that it is organized as 6 3350 disks. Bob's announcement credited "Robert O'Hara, Paul Edwards, and Dave Wade. It is based on earlier versions of VM/370 for Hercules developed by Andy Norrie and Paul Gorlinsky."

Bob and Dave coordinated 4 releases of the SixPack. They are not available from the CBT Tape, but you can download them from Dave Wade's website, via the Internet Archive's Wayback Machine:

2021 to Now: VM/370 Community Edition

In 2021, several folks were preparing a new update to the SixPack system. A discussion ensued about how to name the new system, and they settled on "VM/370 Community Edition".

These distributions are not available from the CBT Tape, but you can download them from the http://vm370.org website. Like the 4, 5, and 6-pack systems, these VM/370 CE distributions are packaged as a ZIP file (e.g., VM370CE.V1.R1.2.zip), and organized for easy deployment using the Hercules System/370 emulator.

Community on Groups.io

Most VM/370 R6 discussion occurs on the Hercules-390 VM mailing list at https://groups.io/g/h390-vm.

RAR

RAR Labs Home page: https://www.rarlabs.com

Free uncompressors for most platforms — pick Extras on the RAR page or go here: https://www.rarlabs.com/rar_add.htm

An unrar package is available in most Linux distributions including Debian.