I believe this problem exists since a long time 
http://mail-index.netbsd.org/port-i386/2002/10/19/0002.html
Also recent thread on "Soekris net4501" shows that boot part from 1.6.2 
fixes the  boot process (but it is not related to memory option).

So I hope to boot my current-NetBSD using /boot, bootxx_ffsv1 from 1.6.2...

Aymeric

Daniel Carosone wrote:

>On Sat, Mar 27, 2004 at 09:05:04PM +0100, Aymeric Arnoud wrote:
>  
>
>>>There's a bug in the way that the MEMORY_DISK is implemented on
>>>i386 (and possibly other platforms) that effectively limits the
>>>size of the memory disk to ~ 10MB.
>>>
>>>(It's a problem that I'd like to see fixed too...)
>>>
>>>      
>>>
>>I would like giving help but don't know where to start ? (it seems to crash far
>>before being able to set a breakpoint)
>>md.c / md_root.c do not change a lot for a quite long time, so any idea about
>>when  the bug appears ?
>>
>>I wonder if MEMORY_DISK_DYNAMIC could be a work-around, how to use it ?
>>    
>>
>
>I hit this problem this week too, did you learn anything more?
>
>--
>Dan.
>