Flasherly said:
Have had an inexpensive Gigabyte MB and AMD Sempron sitting around a
year or so. Finally put the mem, cpu, and dvd to it -- and see in the
(rudimentary) BIOS a provision for something along "turn on virtual"
machines. In the MB book it says something basic about OS that
support virtual machines. Guessing offhandidly that "could be" for
dual cores. Then I go off and stumble upon a read, that all Sempron
productions are dual cores with a core locked. Oh, boy -- a
curveball! Now, if I get lucky I can test whether mine will unlock,
real lucky - for a semi-stable, theoretical, free core. An existing
XP single-core install can't be shifted over to a new machine, a
dually, (hopefully) slipped the new MB drivers and once working (FU-
kludged-BAR), to turn on that BIOS switch, hmmmm... Just asking (a
dream come true, when what "I think" I've heard mentioned, is XP
requires a fresh install for dual core support).
You're mixing a couple concepts together here.
http://en.wikipedia.org/wiki/X86_virtualization
"In computing, x86 virtualization is the facility that allows multiple
operating systems to simultaneously share x86 processor resources in
a safe and efficient manner"
"AMD virtualization (AMD-V)" Pacifica
"Intel virtualization (VT-x)" Vanderpool
"I/O MMU virtualization (AMD-Vi and VT-d)"
Your BIOS setting, could have been turning on/off the Pacifica.
To give an example, I have a copy of Microsoft VirtualPC I run a lot.
I can run a copy of Linux or Windows, inside VirtualPC, while my
regular OS (WinXP) is running. In testing it, I discovered that
hardware virtualization support (can be turned on and off in VirtualPC)
makes no difference at all. What it does make a difference in, is some
Linux LiveCD distros, *crash* depending on the setting used, because
the Linux software tries to "guess" whether it is in a virtual environment
or not.
*******
The other concept, is core unlocking. Or multicore operation.
If you go to Device Manager, (devmgmt.msc), and select the Computer entry,
and do Properties on it, it'll say something like "ACPI Uniprocessor PC".
That uses one core.
If you enabled a second core, and left that setting as is, I don't think the
second core would be used.
If you do a "driver update" on the computer entry, you may be shown which
HAL types are eligible candidates. For example, promotion to
"ACPI Multiprocessor PC" can use more than one core. To work best, it
helps if interrupts are steered with APIC, as even interrupts can be
steered by the OS, to a particular core, for best load sharing.
I think it's possible, that you could leave the Multiprocessor HAL
in place, even if switching back to a single core.
What you have to be careful of, is the "ACPI" part of the Computer entry
in Device Manager. If you disable ACPI in the BIOS, you can force the
OS to respond, by changing the HAL. And then, it will be difficult or
impossible to fix.
So the transition between "ACPI Uniprocessor PC" and "ACPI Multiprocessor PC"
is relatively easy. Whereas, if you find "Standard PC" is the HAL value in
the computer entry, you're in much more trouble. (The last time that
happened to me, I did a Repair Install.)
http://en.wikipedia.org/wiki/Hardware_abstraction_layer
"hide differences in hardware from most of the operating system kernel"
*******
To do core unlocking, you need BIOS support. Perhaps even chipset
support. This is called "Advanced Clock Calibration" or ACC.
This was introduced with a particular AMD Southbridge. I think
perhaps even Nvidia managed to include support on one of their
Southbridge chips.
Later, it was included on other motherboards, but whether it
still needs particular Southbridges, I'm not sure.
http://en.wikipedia.org/wiki/AMD_700_chipset_series#Advanced_Clock_Calibration
AMD also has the option of disabling that entirely. Most likely,
by just removing the core and making the silicon die smaller. It
all depends on whether they feel this feature, reduces demand for
their slightly more expensive processors.
When you enable a second core, it must be tested thoroughly for
stability. I would do that with a Linux LiveCD, rather than messing
up Windows immediately.
Paul