80386 support in -current

John Baldwin jhb at FreeBSD.org
Sat Jan 24 15:41:05 PST 2004

On Saturday 24 January 2004 04:09 pm, Peter Jeremy wrote:
> On Sat, Jan 24, 2004 at 06:40:52PM +1100, I wrote:
> >Does anyone know why FreeBSD 5.x would not run on a 386SX/387SX
> >combination?  I realise the performance would be very poor but I
> >don't see any reason why it wouldn't work at all.
> Based on the responses, I should have included more details.  In my
> defense, I was being dragged out of the house at the time.  This is a
> theoretical question rather than a problem with an actual system.  I
> am aware that the FPU is mandatory (hence the 386/387 combination) and
> I'm aware that I need to build a kernel with "CPU_I386" which then
> can't run on anything else (I meant to state this).
> My question was triggered by reading the 5.2-RELEASE i386 Hardware
> Notes which state that the 80386 is supported but the 80386SX isn't.
> I believe this is a documentation bug - especially since the "80386SX
> isn't supported" was committed about a week after the FPU emulation
> code was axed, though there's no mention of FPU requirements in the
> hardware notes.  I've written a PR (www/61824) but thought I'd double
> check my facts.

This is a docco bug.  Neither 80386[DS]X include a FPU, so a 387 would be 
required in both cases.  However, for 80846's, a 486SX does not include an 
FPU and would require a 487.  The 486 DX does include an FPU and will work 

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

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