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Re: [News] VMware Has Debt to Free Software

Peter Köhlmann <peter.koehlmann@xxxxxxxx> espoused:
> ml2mst wrote:
>
>> Mark Kent schreef:
>>> Peter Köhlmann <peter.koehlmann@xxxxxxxx> espoused:
>>>> Mark Kent wrote:
>>>>
>>>>> Linonut <linonut@xxxxxxxxxxxxx> espoused:
>>>>>> * Tim Smith peremptorily fired off this memo:
>>>>>>
>>>>>>> In article <NEJmk.5818$rD2.1387@xxxxxxxxxxxxxxxxxxxxxx>,
>>>>>>>  Linonut <linonut@xxxxxxxxxxxxx> wrote:
>>>>>>>>> http://www.illuminata.com/perspectives/?p=347
>>>>>>> Basically, it uses Linux as a sort of super-GRUB to set up the
>>>>>>> hardware,
>>>>>>> and load the ESX kernel, then the ESX kernel takes over.  Then,
>>>>>>> cleverly, to get a virtual machine running Linux, to use as a
>>>>>>> management console, it uses that Linux to initialize a virtual
>>>>>>> machine.
>>>>>>>
>>>>>>> This is a very sensible approach.  You are going to use Linux in a VM
>>>>>>> as a management console, so you are going to have a full Linux on the
>>>>>>> disk
>>>>>>> anyway.  That Linux contains code to detect and initialize hardware.
>>>>>>> So, instead of duplicating all that functionality in your kernel, let
>>>>>>> Linux boot the hardware and set it up, then your kernel steps in and
>>>>>>> pushes Linux aside.
>>>>>>>
>>>>>>> IBM did a similar thing in OS/2.  After the BIOS loaded OS/2 and
>>>>>>> started it, OS/2 would create a V86 task, and initialize that with
>>>>>>> the BIOS and
>>>>>>> its state.  Then, if you had hardware that OS/2 did not know about
>>>>>>> but that the BIOS did, OS/2 would use that virtual BIOS to access
>>>>>>> that hardware.
>>>>>>>
>>>>>>> Come to think of it, Windows 95 did a similar thing with DOS.  DOS
>>>>>>> would initialize the hardware, load Windows 95, then Windows 95 would
>>>>>>> virtualize that DOS.
>>>>>> Thanks for that summary and history, Tim.
>>>>>>
>>>>> Windows 95 would virtualise the DOS?  I don't think so.
>>>> It did. Tim is right about that
>>> 
>>> Not as I recall.
>>> 
>>>>  
>>>>>> (Cue some jerk to call me a brown-noser for actually being nice to
>>>>>> someone.)
>>>>> I think his final claim is just wrong.  A "thunk" layer springs to
>>>>> mind, although I forget the details.
>>>>>
>>>> A thunking layer is something different
>>>>
>>> 
>>> I think you're confusing the dos window with the resident DOS 7.
>> 
>> Correct, Windows (up to ME) was loaded as a bunch of extensions on top
>> of DOS.
>> 
>> It was easy to load in plain 16 bit DOS, using the following "trick":
>> 
>> - ATTRIB c:\msdos.sys -r -s -h
>> - EDIT c:\msdos.sys
>> - add in the top section: BootMenu=1
>> - ATTRIB c:\msdos.sys +r +s +h
>> 
>> From now on, you would be presented by a bootmenu, after the bootstrap.
>> So you were able to boot in "plain DOS". How ever, some extensions where
>> loaded by default.
>> 
>> To fire up some DOS games, that required at least 512 KB RAM, you had to
>> choose option  5. from the bootmenu (confirm every step). In which
>> you've had to skip quite a lot. Other wise these games would not work
>> run (insufficient memory).
>> 
>> Unfortunately this option was removed in Windows ME and required a
>> separate boot diskette.
>> 
>> Windows (up to ME) was fully DOS-based.
>> 
>
> Only during boot.
> After Win9x got the drivers loaded and was in control, 

I'm virtually 100% sure that I had to load some DOS drivers to do
certain things in Win95, and that Win95 was able to use those DOS
drivers.  I don't recall the full detail, but that says to me that DOS,
at least some of it, remains after the Win95 "kernel" has booted.

A quick web search throws up loads of examples of mixed DOS/Windows
driver usage, like here:  http://winmac.mvps.org/win95dos.html, indeed,
that particular site talks about "already loaded" drivers being
available once you "exit to DOS", which means to me that they have not
been "virtualised" or anything else, they remain, in memory, where they
were left, and both Windows & DOS can use them.

> the underlying DOS
> was virtualized. 

I do not believe that this statement is correct.  Virtualised versions
of some capabilities were offered by Win95, but there is nothing to
suggest that the DOS which was present at boot up has been
"virtualised", indeed, I'm not sure that you could even do such a thing.

My recollection is that Win95 provided some "equivalent" capabilities,
shifted to "real mode". It's still DOS, of course, but a protected-mode
version.

Now, maybe that's what you meant?

In this context, virtualisation would mean taking what's already loaded
(DOS), and putting a container around it, and moving it somewhere where
it can continue to operate, and providing virtual links back to the rest
of the system.  

This doesn't happen in Win95.

-- 
| mark at ellandroad dot demon dot co dot uk                           |
| Cola faq:  http://www.faqs.org/faqs/linux/advocacy/faq-and-primer/   |
| Cola trolls:  http://colatrolls.blogspot.com/                        |
| Open platforms prevent vendor lock-in.  Own your Own services!       |


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