[fpc-devel] Re: fpc-devel Digest, Vol 112, Issue 32

Mark Morgan Lloyd markMLl.fpc-devel at telemetry.co.uk
Fri Aug 23 22:50:33 CEST 2013

Mark Morgan Lloyd wrote:

> Quite frankly, from what I've seen most Windows users would find Linux 
> simpler than one of the *freely* *available* IBM OSes (i.e. MVS, VM/360 
> "sixpack" and so on).

To avoid ambiguity: that was a typo, and I meant "VM/370 'sixpack'".

As background: it appears that IBM didn't embed copyright notices in the 
source or binary of their early operating systems, with the result that 
older versions of the DOS, OS, and VM lines are now described as being 
in the public domain. There's a hobbyist community that runs these under 
the Hercules emulator, IBM is aware of this but generally keeps its 

All of these date back to the era when addresses (certainly per-process, 
and usually system-wide) were 24 bit, i.e. there was a process or system 
restriction of 16Mbyte of "core". Unfortunately, GCC can't compile 
itself in 16Mb, so somebody's created a patch for the Hercules emulator 
and for the operating systems which allows one program at a time to 
allocate storage from "above the line", this is referred to as the /380 
hack http://mvs380.sourceforge.net/ and hardly anybody's happy about it.

Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]

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