M2N32-SLI Deluxe with ECC-RAM hangs with new BIOS

[Anacunga]

Situation: ASUS M2N32-SLI Deluxe / Wireless Edition Rev. 1.03G (originally with BIOS 0603) and 4GB of ECC-RAM (4x 1GB double-sided HP P/N 445166-051 – 1GB 2Rx8 PC2-6400E-666-12 - one of them Hynix, three of them Samsung, but all have same HP-P/N).

Was working so far without any issues for quite a while with Athlon64 X2 4200.

CPU should be replaced by Phenom X4 9750/9850 or Athlon64 X2 6000+ (G2-stepping 3100MHz)

Problem to expect with BIOS 0603: no support of new CPU

OK - BIOS updated (still with Athlon64 X2 4200) to last BIOS 5002

Result: boot hangs at RAM (displayed by code of PCI-test-card for debugging)

RAM replaced by non-ECC single-sided 2x 512MB ... working.

Then flash-downgraded every BIOS available (!) step-by-step (with Athlon4200/nonECC-RAM) and tested with ECC-RAM: working is only BIOS 1701 and BIOS 1603 - downgrade to lesser BIOS is not allowed (why???) and not possible, so last working BIOS with mentioned ECC-RAM is 1701; officially Athlon64 X2 6000+ G2-stepping is not suported with that BIOS (but working and correctly recognized/displayed) ... officially BIOS 2001 needed for that CPU

No FAQ found for that issue – presented to ASUS-Support: got answer from ASUS-Support in Germany: I have to use only RAM from QVL and no other RAM ...

Question:possible to modify last BIOS (5002) to cooperate with mentioned HP P/N 445166-051 (1GB 2Rx8 PC2-6400E-666-12) ECC RAM?

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Btw: problem described here: http://vip.asus.com/forum/view.aspx?board_id=1&model=M2N32-SLI+Deluxe&id=20111128220355305&page=1&SLanguage=en-us