Date: Sat, 20 Feb 1999 03:12:12 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: idiotswitch@beer.com Cc: current@FreeBSD.ORG Subject: Re: AMD K6-2 for smp Message-ID: <199902200312.UAA25219@usr02.primenet.com> In-Reply-To: <002001be5bfe$f3d9a360$0a00000a@a19.my.intranet> from "IdiotSwitch Editor" at Feb 19, 99 06:56:54 am
next in thread | previous in thread | raw e-mail | index | archive | help
> I understand that you can purchase special motherboards (probably only from > AMD) for SMP K6-2's (possibly they'll take -3's as well). I doubt (without > trying) the freebsd code supports this style as it's not done in the normal > fashion. They kind of cheated the chips into working together. Not a great > system. Either get a twin PII, or wait for the K7's (but that won't be > cheap). It is my understanding that the K7's require "OpenAPIC". The SMP code would need to be updated for the non-APIC based implementation for the K7's. It's also my understanding that the K6 SMP architectures use the "BeBox" PPC 603 SMP hack (the PPC 604's used in the SMP Apple boxes have "processor attention" pins, and so don't suffer this handicap). The hack involves using an ASIC in place of the L2 cache controllers that would normally be associated with the chip. The result is that the combined system supports only MEI cache coherency, instead of MESI cache coherency. FreeBSD's SMP really, really depends on MESI. Really. This means that it would be very hard to port a working SMP over to another architecture (e.g. SPARC, like Linux has), without abstracting the cache coherency code out as a seperate (NULL on Intel) layer. In many ways, it was bad to do SMP on Intel MPSpec compatible hardware, instead of starting with lesser hardware and porting, since the implementation is tied to the spec (for now). Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199902200312.UAA25219>