BIOS that can skip memory test?

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We are looking for an X86 ETX board with a BIOS that can be set to *not*
execute a memory test.

The reason is that we want to use the upper part of RAM as a nonvolatile
area to store logs.  These units won't lose power, but should one crash and
reboot, we want to look in the logs and see what happened just before the
crash.  We don't want it trashed between boots.  These boxes run Linux, and
the kernel has a "mem=" parameter to keep it away from the nonvolatile area.
Linux seems to be able to behave accordingly, but we're having trouble with
the BIOS.

Thanks.




Re: BIOS that can skip memory test?
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and
and
area.
with

I think -- and let me emphasize *think* -- that BIOS will stop its memory
test as soon as it finds a "hole".  If you could find some way to skip an
address range between the real top of RAM and your stuff, I think that most
BIOS will never find it.

    Norm


Re: BIOS that can skip memory test?

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most

Thanks.  I think you're right.

Our problem is that we want to use an off-the-shelf, commercial processor
board with 512M memory, which is going to be one contiguous DDR module.  We
want to reserve the last 32M of the core memory for this pseudo-nonvolatile
storage.  So, I'm looking for some way to do it when there is no hole.




Re: BIOS that can skip memory test?
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ISTR that this issue was discussed here, or maybe in
sci.electronics.*, a while ago (meaning some time in the last two
years) and the consensus was that even at warmboot, the motherboard
chipset is completely reset - which interrupts RAM refresh. Therefore,
you cannot rely on anything remaining in RAM across a warm-boot, even
if the BIOS is fiddled with so it doesn't intentionally trash the
upper area.

Re: BIOS that can skip memory test?

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How is it forced to reboot?

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Before testing the memory, BIOS initializes the memory and controller which
causes the memory to lost its content. It might be impossible to do what you
want. Why don't you store the logs in some nonvolatile memory, like a flash
"key" or flash memory card?



Re: BIOS that can skip memory test?
On Thu, 30 Sep 2004 08:42:52 +0200, "Grzegorz Mazur"

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Yes, it needs to first size the existing memory.  So, good point.

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First problem that comes to mind is that they probably don't want to incur the
write-delays.  There is always some kind of lag going on between the RAM buffers
(which are sure to be destroyed on boot) and the flash writing process, which
may be a bit behind.  Particularly, if they need to write a lot of data quickly.
I just went through a similar problem in writing high speed data logs to flash
and had to give up and just use the extremely large RAM, because it was fast
enough and the flash simply was not.  They may really need the more recent
information, in fact, for their post-mortems.

Use to be some old IBM PC cards had battery backed static RAM on them, when ISA
bus memory was "the thing."  Might be they need to set up something similar,
though preferably on the PCI (going over the south bridge isn't optimal.)
Perhaps take your suggestion, kind of, except modify the BIOS itself so that it
saves the last known good RAM configuration to the CMOS timer/parameter chip
(where the warm-start byte is also stored) and restore the chipset controller's
arrangement on restart and without any destructive follow-up.  Of course, you'd
want BIOS source to poke away at.

Tricky.

Jon

Re: BIOS that can skip memory test?
: On Thu, 30 Sep 2004 08:42:52 +0200, "Grzegorz Mazur"
:
:>Before testing the memory, BIOS initializes the memory and
:>controller which causes the memory to lost its content.
:
: Yes, it needs to first size the existing memory.  So, good point.
:
: Use to be some old IBM PC cards had battery backed static RAM
: on them, when ISA

Easiest solution yes, if you can find a PCI memory card.

: [SNIP] arrangement on restart and without any destructive follow-up.
: Of course, you'd want BIOS source to poke away at.

And the only BIOS source code that is (legally) in the
public domain is the original IBM AT BIOS. Useless.

But then again, why not choose the path less traveled -
implement the emebdded solution. That is, rid yourself
of the BIOS alltogether and burn the Linux kernel plus
minimalistic initialisation into the flash chip. Or
use one of the Open Source BIOS replacement projects.
Never done this myself, though...


     http://www.linuxbios.org /
     http://www.openbios.org /


--
  ******************************************************
  Never ever underestimate the power of human stupidity.
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Re: BIOS that can skip memory test?
: : On Thu, 30 Sep 2004 08:42:52 +0200, "Grzegorz Mazur"
: :
: :>Before testing the memory, BIOS initializes the memory and
: :>controller which causes the memory to lost its content.
: :
: : Yes, it needs to first size the existing memory.  So, good point.
: :
: : Use to be some old IBM PC cards had battery backed static RAM
: : on them, when ISA
:
: Easiest solution yes, if you can find a PCI memory card.

Come to think about it - this might very well prove to be the only solution
unless you can somehow prevent the hard reset line from beeing asserted.
If not, then the memory controller will be reset no matter what software
there is in the flash chip and memory content will surely be lost.

This is payback time for choosing COTS hardware...

--
  ******************************************************
  Never ever underestimate the power of human stupidity.
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Re: BIOS that can skip memory test?
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... snip ...
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That may be published, but it is not in the public domain.  That
fact was the origin of Phoenix, whose original business was
writing non-IBM-copyrighted bioses for clones.  Before that was
done IBM forced many clone manufacturers out of business with
licensing demands.

--
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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Re: BIOS that can skip memory test?


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We did a board for a customer with a similar setup to the PC cards - SDRAM
hooked to an FPGA along with PCI, a lot of NAND flash and some batteries.
Data is normally stored to the SDRAM, when power fail is detected the FPGA
automatically dumps the data into NAND flash and manages the bad sector
mapping and error correction codes.  The batteries are sized to sustain
operation until the save is complete.  On power up the data is restored
and various flags and error status are forwarded back to the host CPU.

If anyone is interested e-mail me and I'll see if we have the rights to
re-sell that design or can license it from the original customer.



Re: BIOS that can skip memory test?
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Previous answers point out that this will probably not work, because the
RAM contents are already gone before the BIOS even starts up.

To me, this sounds like the perfect excuse to finally buy a
solid-state hard-disk (i.e. gobs of RAM forming a SCSI device).

--
Hans-Bernhard Broeker ( snipped-for-privacy@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

Re: BIOS that can skip memory test?
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Search for 'linuxbios' is an opensource project that has 100% sources
for many mobo...

Alternatively, if you are building your board, you can use these as a
starting point to develop your own bios....

goodluck

James



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