Re: Is DDR ram backward compatable with DDR3 slots
- From: Paul <nospam@xxxxxxxxxx>
- Date: Fri, 01 Oct 2010 11:58:09 -0400
Bob H wrote:
I have had to replace a cpu on a LGA775 board which has 2gb of DDR Corsair ram fitted. The new cpu produces an error (uCode)on booting , from which I read that generally means a BIOS update. The BIOS on the board is bang up to date and there is no further updated from Asus's site.
For the moment I can live with having to press the F1 key each time the system boots up, but I would rather not have to so that means another board.
Most if not all of the boards I have looked at (Asus), are for DDR3 ram, so I wondered if I could use such aboard for DDR ram.
If you're a glutton for punishment, there is always this motherboard.
This is good, at all stock settings. It's not a good choice for
overclocking (since the code controlling the clock generator is
wrong). The clock generator works fine at defaults, as the default
conditions are controlled by the BSEL lines coming from the processor.
The BSEL lines indicate the FSB speed (800, 1066, 1333 etc).
That board is what I used, when I wanted to have a Core2 processor,
but without dumping my AGP video card. It accepts DDR memory.
It also takes DDR2, which is what I ended up using.
The DDR2-667 rating is likely a crock - it's stable
and bulletproof when running at DDR2-533 though. Mine
threw errors at the DDR2-667 speed setting.
(You can plug in DDR2-800 if you want, and dial it to
DDR2-533. That is what I did for my DDR2 RAM.) In fact,
the memory subsystem has a lower error rate, than my
previous Intel chipset motherboard. So no complaints
about crashing or errors.
The FSB is limited to FSB1066, so you kinda have to plan
for usage of that motherboard in advance. If you have an
FSB1333 processor, then that motherboard would be a poor
choice. But it is one of the few I know of, that take
the older memory type. It has plenty of legacy features.
I'd be using it today, except for one "feature" of the BIOS
I simply couldn't live with.
You also have the option of buying new memory. Buying
new memory, means you can buy the motherboard you
really wanted :-) And not wasting your time "making"
a real motherboard out of that thing, is worth something.
There is a way to patch microcode. We used CTMC at
one time, to patch in a microcode on an Award BIOS.
The CTMC procedure has the advantage of being
relatively safe - you're not likely to break a
BIOS using it. That's why I liked it. it is not
as dangerous as flashing an entire BIOS. This is a
web page from that era, to give you the flavor
of the process used.
I'm not aware of anyone using that recipe on modern
systems, and I don't know whether the CTMC program
anticipated the fact that the microcode length is
no longer fixed length any more. Back when that
program was being used, all the microcode segments
were 2KB. Now, they can be other lengths.
The BIOS has an opportunity to load a microcode patch.
The BIOS is a miniature file system, and one of the
files inside the BIOS, is a file full of microcodes.
At one time, there would be about eight different
microcodes stored in the file. The processor will
only accept a microcode with matching family code
details, and a good checksum. So the processor is
protected against accepting crap. The BIOS uses its
collection of microcodes, to try and load a patch.
The patch, may correct design errors in the processor.
Since there are no release notes for microcode,
we'll never know how serious the errors are.
Normally, the BIOS would contain microcode for
all the processors supported. In some cases, a new
processor would come along, it would pass all other
recognition steps, but there wasn't a matching
microcode. Then, you get that error, as the BIOS
doesn't succeed in applying one of its patches.
But all is not lost. Modern OSes have a microcode
loader of their own. As long as your computer
can survive, until boot is complete, then it'll get
some microcode anyway. In your case, as you've seen,
it's a cosmetic issue.
If you look in the BIOS, there may be a "stop on all errors",
"stop on no errors", "stop on keyboard error" type setting.
If you set that to "stop on no errors", it might stop
pestering you. And then the OS microcode loader will
solve the problem for you. If the computer was crashing,
before the OS completed booted, *then* you'd have a problem
that needed fixing. I think a flipping of that "Stop on"
setting, and you're done.
To test whether a microcode patch is present, you can use
the Intel Processor Identification Utility. Under "CPUID Data"
is a "CPU Revision" field. A value of 00, means neither
the BIOS, nor the OS, succeeded in patching the processor.
Mine is 07 right now, that tells me a patch of revision 7
was applied (somehow). My assumption would be the BIOS
did it, but I could be wrong. I'd have to tear apart the
BIOS, to be absolutely sure that is where it came from :-)
The CPU Revision is the revision number of the patch used.
The OS microcode loader is sneaky - it doesn't need to
stick around after the OS is running. The description
here isn't important - just the name is worth mentioning
if you need to do further research.
"Description of the Microcode Update device"
- Is DDR ram backward compatable with DDR3 slots
- From: Bob H
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