Date: Sat, 23 Dec 2000 14:08:09 -0500 From: Sergey Babkin <babkin@bellatlantic.net> To: Mike Smith <msmith@freebsd.org> Cc: heckfordj@psi-domain.co.uk, freebsd-hackers@freebsd.org Subject: Re: Pentium 4 Message-ID: <3A44F819.D2A5D8AC@bellatlantic.net> References: <200012222338.eBMNcfj06065@mass.osd.bsdi.com>
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Mike Smith wrote: > > > Mike Smith wrote: > > > > > > > Is there now support for the Pentium 4 in FreeBSD?? > > > > > > We've always run on the P4. > > > > > > > If so, is there an option such as CPUCLASS 786 in the Kernel?? > > > > > > No, it's still a 686. > > > > Basically, there are 3 possible issues for Pentium4: > > > > - higher clock frequency (also for newer P3) may cause overflow > > in counters of delay loops - hopefully this does not happen in > > FreeBSD > > We calibrate our delay loops. 8) If not enough bits are allowed to store the calibrated value then there will be overflows with bad consequences - delays may take almost forever. UnixWare had a problem of this sort with CPUs > ~800MHz. I suppose FreeBSD does not. > > - microcode download: it got new model ID, so minor tweaking may be > > needed to make sure that Pentium4 is recognised as upgradable > > (this depends on how model comparison is done for example, Linux > > needed this tweaking, UnixWare did not) > > FreeBSD doesn't do microcode download; it is expected that the platform > BIOS will do this (since the download is an Intel trade secret, we are > unlikely to ever do this). Well, the process of download itself is published, look at the IA-32 specs at the Intel development site - they include this information and information on P4 in general except the Jackson (two CPUs on one chip) technology which is for now NDA-only. I'm not sure what license Intel attaches to the microcode images it distributes. I think it prohibits to use it for any purpose except than updating the genuine Intel CPUs but otherwise may be downloaded freely, but I'm not sure. > The Linux issue was actually more stupid than that; Linux won't run on a > CPU it doesn't recognise. FreeBSD will only refuse to run on a CPU it > recognises as incapable (since that is a much smaller set). As far as I understood from the explanation I got from a preson at Intel, Linux did not compare the CPU model field and used only the stepping (or something like this) field of the identification MSR. So it recognised P4 as the very first stepping of PentiumPro and thus not having the microcode upgrade feature. -SB To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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