memory disk, evbarm - lubbock

[Stewart Heitmann <S.Heitmann%lake.com@localhost>]

I am trying to create a memory disk within the kernel
for the evbarm port to the LUBBOCK eval board.
(LUBBOCK is Intel's DBPXA250 eval board for the XScale CPU). 
Ultimately I want to put the root filesystem on the memory disk,
but have got that far yet because I cant make the memory
disk large enough.

I can compile a kernel with up to 4096K space set aside
for the memory disk, but when I try to make it larger I
get a kernel panic. 
Oddly enough, when I make it much much larger (16384K or more)
the kernel boots ok, but /sbin/init seg faults.

Is there a limit on the size of a memory disk?
I'd like to make one about 30MB, is that a silly thing to try???

For the record, my kernel config has:
        options                 MEMORY_DISK_HOOKS                       #
boottime setup of ramdisk
        options         MEMORY_DISK_SERVER=0            # no userspace
memory disk support
        #options                MEMORY_DISK_IS_ROOT             # use memory
disk as root (disabled for now)
        options           MEMORY_DISK_ROOT_SIZE=8192    # (md0=4096K)

        # disk/mass storage pseudo-devices
        pseudo-device   md              1                       # memory
disk device (ramdisk)

My config file has other options that no longer seem to have any effect,
and I cant find any reference to them in sys/dev so I believe they are
redundant. Can anyone confirm these are no longer required?
        #options        MEMORY_DISK_SIZE=3072   # Size in blocks
        #options        MINIROOTSIZE=1000               # Size in blocks


Stewart Heitmann <s.heitmann%lake.com@localhost>