poweredge 1850 won't boot 7.1? maybe LSI-related : amr0: adapter is busy

[Olivier Mueller]

Hello,

This afternoon I wanted to upgrade to 7.1 two good old dell PowerEdge
servers which were running FreeBSD 6.x.  It went fine and quickly on the
poweredge 1950, but it failed completely on the poweredge 1850. 

Facts:

- boot cd and setup / operation of freebsd 6.x or 7.0 is fine
   Message log abstract: 
	$ uname -v
	FreeBSD 7.0-RELEASE-p7 #0: Sun Dec 21 08:31:52 UTC 2008     root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC 
	$ dmesg|grep amr
	amr0: <LSILogic MegaRAID 1.53> mem 0xd80f0000-0xd80fffff,0xdfde0000-0xdfdfffff irq 46 at device 14.0 on pci2
	amr0: Using 64-bit DMA
	amr0: [ITHREAD]
	amr0: delete logical drives supported by controller
	amr0: <LSILogic PERC 4e/Si> Firmware 521X, BIOS H430, 256MB RAM
	amr0: delete logical drives supported by controller
	amrd0: <LSILogic MegaRAID logical drive> on amr0
	amrd0: 69880MB (143114240 sectors) RAID 1 (optimal)
	Trying to mount root from ufs:/dev/amrd0s1a

- boot cd of 7.1 fails because the installed doesn't see any harddisk. 
   Message log abstract:
    	amr0: adapter is busy
	amr0: adapter is busy
	amr0: delete logical drives supported by controller
 

I also tried to setup 7.0, and then upgrade to 7.1 with freebsd-update,
but then it fails exactly like with the 7.1 boot CD
(7.1-RELEASE-amd64-disc1.iso). Screenshot: 
     http://omx.ch/om/stuff/pe1850bsd71error.jpg

BIOS Message about the Controller on system startup:
PowerEdge Expandable RAID COntroller BIOS, (c) 2006 LSI Logic
Corporation

I'm not sure what I can try next...  I'd still like to be able to run
7.1 on this host as well as on several other old but still fine 1850. Is
my system simply too old?  Why is my adapter "busy" under 7.1?  What
would you try?   I checked the relnotes as well, but saw nothing helpful
about my problem there.

regards & thanks in advance for any feedback,
Olivier