docs/77304: FreeBSD 5.3 can not be installed on a 16 MB old pentium 75 MHz machine.

[John Baldwin]

On Wednesday 09 February 2005 07:01 am, Ramiro Aceves wrote:
> >Number:         77304
> >Category:       docs
> >Synopsis:       FreeBSD 5.3 can not be installed on a 16 MB old pentium 75
> > MHz machine. Confidential:   no
> >Severity:       non-critical
> >Priority:       low
> >Responsible:    freebsd-doc
> >State:          open
> >Quarter:
> >Keywords:
> >Date-Required:
> >Class:          doc-bug
> >Submitter-Id:   current-users
> >Arrival-Date:   Wed Feb 09 12:10:23 GMT 2005
> >Closed-Date:
> >Last-Modified:
> >Originator:     Ramiro Aceves
> >Release:        5.3 Release
> >Organization:
>
> none
>
> >Environment:
>
> FreeBSD freebsd.remigio 5.3-RELEASE FreeBSD 5.3-RELEASE #1: Wed Jan 19
> 03:22:06 CET 2005 root at freebsd.remigio:/usr/src/sys/i386/compile/MIKERNEL 
> i386
>
> >Description:
>
> FreeBSD 5.3 can not be installed from floppies in a 16 MB RAM old Pentium
> 75 MHz machine. It just reboots after pressing return on the beastie
> screen,not showing any kernel messages.
>
> The docs placed into the "floppies" directory on the CDROM say:
>
>         1.2 Hardware Requirements
>
> FreeBSD for the i386 requires a 486 or better processor to install         
>   and run(although FreeBSD can run on 386 processors with a custom
> kernel)and at least 8 megs of RAM to install and 7 megs to run.
>
> >How-To-Repeat:
>
> Just boot from the floppies. Wait until the beastie logo comes. Press
> return or wait for 10 seconds. It reboots.
>
> >Fix:
>
> Add more memory. 32 MB RAM work perfectly here. I have not tested 24MB.
> I think the docs should be updated.
> Thank you very much.

Yes, they should.  I looked at my 5.3 CD and the kernel and uncompressed 
mfsroot are:

-r-xr-xr-x  1 root  wheel  5828080 Nov  4 23:19 kernel/kernel
-rw-rw-r--  1 john  wheel  4423680 Feb  9 11:09 /tmp/mfsroot

One of the changes in 5.x is to load the kernel at a physical address of 4mb 
rather than 1mb to work around bugs with PSE and PGE on certain CPUs, so that 
means you have to have 4mb + kernel + mfsroot.  Also, the kernel includes 
bss, so the real size for the kernel is:

   text    data     bss     dec     hex filename
4416289  510984  327200 5254473  502d49 kernel/kernel

Adding it all up comes out to 13872457 bytes, which is just over 13MB 
(13631488 bytes).  However, the kernel requires some amount of memory that it 
allocates during very early startup for things like page tables and it 
allocates that stuff at the end of the kernel + modules, so that all has to 
come from the remaining 2+ MB, which is probably not enough memory.  I do 
think 24MB should be the minimum to install.  The minimum to run using a 
stripped down kernel without an mfsroot is probably still very small, though 
I'm not sure 7MB would cut it.  Probably at least 12MB or so.

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org