Date: Wed, 16 Jul 1997 18:50:26 -0600 From: vanmaren@fast.cs.utah.edu (Kevin Van Maren) To: smp@csn.net Cc: smp@FreeBSD.ORG Subject: Re: self modifying kernel code Message-ID: <199707170050.SAA28284@fast.cs.utah.edu>
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> Hi, > > oops, I hit the 'send' button too soon, sorry... anyways: > > > Hey, we have a dual 486 VTECH box that I would love to run SMP freebsd on... > > It used to run NT fine on dual CPUs, but is not running uniprocessor Linux. > > > > But you are right, it is obsolete hardware. > > I hate to be a grinch, but IMHO we can't spend resources to support > maybe 6 or 7 potential users's of such hardware. I'm sure no one > would object to someone adding such support on their own (assumming it > could be done in such a way as to add NO overhead to the generic SMP kernel). > I have no idea how much effort we are talking about ... The only big deal with it is that the APICs are all at different addresses -- you have to know which CPU you are on to know what address to use. With the `logical' CPU mapping, that shouldn't be too difficult. The other difficulty is in startup. With the external APIC, you can't just send the startup IPI. It's not difficult, and well documented, but I've never tried to deal with it. Maybe when I have a day or two with nothing else to do, I'll play with it again. Oh, one more thing. There isn't a mptable -- it would have to be `hard coded' based on recognition of the machine. Not a big deal; it doesn't have PCI or anything. But I do have the recognition code for the machine. I don't expect you to try to get it working. However, I do think that the SMP framework should be kept sufficiently generic that it could deal with APICs at different addresses (not they are withing the same physical page, sp mappings don't help) as we can't tell what will happen in version 2.0. The ability to handle different addresses (for IOAPICS) already needs to be added. Kevin
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