[Oberon] early ports of Oberon

Paul Reed paulreed at paddedcell.com
Mon Jan 11 17:18:30 CET 2021

Hi Joerg,

I agree with Liam, definitely not the same thing.

The initial ports of Oberon to other operating systems would not today 
commonly be classed as virtualisation; they implemented Oberon as an 
application, and had to contend in various ways with different 
underlying I/O and filesystem semantics in ad-hoc ways. This could be 
done because Oberon as an operating system is so simple, it wasn't 
difficult to convert it to an application.

So sure, it's "virtualisation" in some wider sense, but not 
virtualisation as we know it, Jim. :)

Furthermore, a hypervisor may emulate, but it is not an emulator...


On 2021-01-11 15:37, Joerg wrote:
> Liam
> In my point of view, it boils down the basic question whether you
> define a "hypervisor" being an emulator or not __
> br
> Jörg
> Am 11.01.21, 16:29 schrieb "Oberon im Auftrag von Liam Proven"
> <oberon-bounces at lists.inf.ethz.ch im Auftrag von lproven at gmail.com>:
>     On Mon, 11 Jan 2021 at 16:13, Joerg <joerg.straube at iaeth.ch> wrote:
>     >
>     > Today, this is also called "virtualization" with a HostOS and a
> GuestOS (=Oberon System)
>     Not the same thing.
>     Full-system virtualisation, that is a hypervisor such as KVM, Xen,
>     VMware or VirtualBox, basically means an emulator that emulates an
>     entire computer _on the same computer architecture_.
>     This is a built-in feature of SPARC, IBM POWER etc. It was not a
>     feature of x86 until Intel added its VT feature (and AMD its AMD-V)
>     around 2005-2006. This adds a "ring -1" underneath Ring 0, the
>     "supervisor mode" of traditional x86.
>     Linux' KVM uses the VT/AMD-D feature and cannot work without it.
>     Similarly, Microsoft's Hyper-V does the same.
>     But Hyper-V evolved from a program called Virtual PC, which is 
> still a
>     free download from MS:
>     https://www.microsoft.com/en-us/download/details.aspx?id=3702
>     MS acquired Virtual PC when it acquired Mac vendor Connectix.
>     VirtualPC originated as a Mac software emulator allowing you to run 
> PC
>     OSes as programs under Classic MacOS on PowerPC processors.
>     In other words, a hypervisor is just a special case of an emulator: 
> it
>     emulates a platform _on the same platform_.
>     But inside a hypervisor's VM, you have a whole empty PC complete 
> with
>     emulated BIOS, emulated disks, emulated RAM, emulated graphics 
> card,
>     emulated network interface, etc.
>     Oberon runs like this, sure. But so can any PC OS.
>     Oberon _also_ runs as a program on top of other OSes. For example 
> here
>     is a Mac version:
>     https://apps.apple.com/us/app/oberon-core/id1057155516?mt=12
>     This is an emulator, not a VM. It emulates a RISC5 computer, in a
>     resizable window.
>     It also runs _as a program_ on top of Windows, Linux and macOS.
>     Downloads are here:
>     https://github.com/metacore/A2OS
>     This does not use a hypervisor or a VM. This is the OS built as a
>     program to run on top of another OS.
>     A closer comparison is User Mode Linux on top of another Linux 
> distro:
>     https://en.wikipedia.org/wiki/User-mode_Linux
>     Or CoLinux on Windows:
>     https://en.wikipedia.org/wiki/Cooperative_Linux
>     To the host OS, these are not VMs, they are programs. But the
>     "program" is an OS and to apps inside the program, they are running 
> on
>     their own system, not on the host OS.
>     So I am not saying you are _wrong_ -- I am saying _both_ are true.
>     There is a version for hypervisors, that runs in a VM, *and* there 
> are
>     native versions that run on Windows, Linux and macOS. They are
>     different entities. The hosted versions can't run in a VM, and the
>     bare-metal version will not execute under another OS.
>     --
>     Liam Proven – Profile: https://about.me/liamproven
>     Email: lproven at cix.co.uk – gMail/gTalk/gHangouts: lproven at gmail.com
>     Twitter/Facebook/LinkedIn/Flickr: lproven – Skype: liamproven
>     UK: +44 7939-087884 – ČR (+ WhatsApp/Telegram/Signal): +420 702 829 
> 053
>     --
>     Oberon at lists.inf.ethz.ch mailing list for ETH Oberon and related 
> systems
>     https://lists.inf.ethz.ch/mailman/listinfo/oberon
> --
> Oberon at lists.inf.ethz.ch mailing list for ETH Oberon and related 
> systems
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