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Invisible wrote:
> Until yesterday, the only products I'd heard of where Bochs (only runs
> on Linux) and VMware (AFAIK that's extremely expensive).
I was wrong: Apparently Bochs now runs on Windoze too. (And indeed, QEMU
is using the Bochs BIOS code, and both use the same VGA BIOS.)
However, Bochs looks significantly more complicated to set up...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Invisible wrote:
>>> Also - virtual machines are SOOOO SLOOOOOW... :-/
>>
>> They aren't that slow. Thing is, you're using QEMU, which isn't a virtual
>> machine, it's an emulator. Software like VMware or VirtualBox use your
>> real
>> CPU instead of basically executing x86 code on an interpreter.
>
> Presumably that requires *very* specialised hardware though?
I was right:
http://en.wikipedia.org/wiki/X86_virtualization
Hardware-assisted virtualisation is a feature found only on the very
newest CPUs from Intel and AMD.
That still leaves open the question of how some products claim to
virtualise without emulation on CPUs that lack this technology.
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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>>> So when you say "works on any reasonably modern PC", what you
>>> *actually* mean is "works on any brand new bleeding-edge PC"?
>>
>> No. I believe it was the 386 that added the capability.
>>
>> You know, two generations back before the Pentium came out?
>>
>> Added primarily to emulate multiple "DOS boxes" under Windows.
>
> The 386 or so added "virtual mode" (or whatever the exact term is) that
> makes the CPU act as if it's in real mode, but it's really in protected
> mode, and the OS can control the page mappings and so forth.
"Virtual real mode".
http://en.wikipedia.org/wiki/Virtual_8086_mode
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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> Nope, I was wrong. Apparently it uses a 4 MHz customised Z80 with an
> on-die ROM for bootstrap and a customised instruction set somewhat similar
> to the Intel 8080... Oh well!
Oh and Wikipedia tells me the TI-86 has a 6 MHz Z80, so I guess not straight
copy of game-boy apps, some hacks probably needed for timing etc. Or maybe
the games just ran a bit 50% faster, I can't remember.
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Invisible wrote:
> PS. Yes, I'm playing Doom at work. And? ;-)
>
S0 you are human after all :-)
John
--
"Eppur si muove" - Galileo Galilei
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Doctor John wrote:
> Invisible wrote:
>> PS. Yes, I'm playing Doom at work. And? ;-)
>>
> S0 you are human after all :-)
Actually, in truth I was watching the demo. The framerate is a bit too
low to actually "play" the game. (Plus I don't know the controls.)
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Invisible wrote:
> Doctor John wrote:
>> Invisible wrote:
>>> PS. Yes, I'm playing Doom at work. And? ;-)
>>>
>> S0 you are human after all :-)
>
> Actually, in truth I was watching the demo. The framerate is a bit too
> low to actually "play" the game. (Plus I don't know the controls.)
>
IIRC the key bindings are configurable. OTTOMH <ESC> in the splash
screen pulls up a menu and I think options in that menu leads you to key
bindings. Don't quote me on that though
John
--
"Eppur si muove" - Galileo Galilei
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"Invisible" <voi### [at] dev null> wrote in message
news:48bd22a1$1@news.povray.org...
>>
> That still leaves open the question of how some products claim to
> virtualise without emulation on CPUs that lack this technology.
>
Quote, from the wiki page you linked
"VMware and similar virtualization software for the x86 must employ binary
translation techniques to trap and virtualize the execution of certain
instructions. These techniques incur some performance overhead as compared
to a VM running on a natively virtualizable architecture"
http://en.wikipedia.org/wiki/Binary_translation
Also see
http://en.wikipedia.org/wiki/Operating_system-level_virtualization
The hardware extensions is what makes the hypervisor type products (that run
'beneath' the OS possible). You'll need that for things like Server 2008's
hyper-V, VMWare's ESX server (which can make do without), Xen and others.
Things like VMWare workstation can use it but don't need it. MS's Virtual PC
can't use the hardware emulation at all, though Virtual Server can
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Gail wrote:
> Quote, from the wiki page you linked
>
> "VMware and similar virtualization software for the x86 must employ
> binary translation techniques to trap and virtualize the execution of
> certain instructions. These techniques incur some performance overhead
> as compared to a VM running on a natively virtualizable architecture"
Right. So it only emulates some instructions, instead of all of them?
> The hardware extensions is what makes the hypervisor type products (that
> run 'beneath' the OS possible). You'll need that for things like Server
> 2008's hyper-V, VMWare's ESX server (which can make do without), Xen and
> others.
>
> Things like VMWare workstation can use it but don't need it. MS's
> Virtual PC can't use the hardware emulation at all, though Virtual
> Server can
I've spent some time looking at all the various products out there. It
seems that QEMU is the only one that can be run without "installing"
anything. Some install special kernel-mode drivers, others run on the
bare metal beneigh the first "privilaged" OS, but I'm not seeing
anything else that you can throw on a USB stick and use anywhere. (I
also note that several of these things appear to be "based on" QEMU...)
Still, if I was trying to offer hosting of virtual servers, this would
be a non-issue.
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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Invisible wrote:
> You can use that to make real mode applications (e.g., DOS programs)
> think they have the machine to themselves. But that doesn't work for a
> protected mode program such as an OS.
I stand corrected. :-)
--
Darren New / San Diego, CA, USA (PST)
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