From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailserv2.iuinc.com (qmailr@mailserv2.iuinc.com [206.245.164.55]) by puffin.external.hp.com (8.8.7/8.8.7) with SMTP id KAA26115 for ; Tue, 19 Oct 1999 10:04:07 -0600 Received: from milano.cup.hp.com (root@milano.cup.hp.com [15.16.124.11]) by atlrel2.hp.com (8.8.6 (PHNE_17135)/8.8.5tis) with ESMTP id MAA18876 for ; Tue, 19 Oct 1999 12:04:01 -0400 (EDT) Received: from localhost (grundler@localhost [127.0.0.1]) by milano.cup.hp.com with SMTP (8.8.6 (PHNE_14041)/8.7.3 TIS Messaging 5.0) id JAA27382 for ; Tue, 19 Oct 1999 09:04:42 -0700 (PDT) Message-Id: <199910191604.JAA27382@milano.cup.hp.com> To: parisc-linux@thepuffingroup.com Subject: Re: [parisc-linux] different PA2.0 CPUs in the same box? In-reply-to: Your message of "Mon, 18 Oct 1999 22:31:15 PDT." <199910190531.WAA27190@milano.cup.hp.com> Date: Tue, 19 Oct 1999 09:04:41 -0700 From: Grant Grundler List-ID: Grant Grundler wrote: > Alex deVries wrote: > > > > Can you mix and match different PA2.0 CPUs in a multiprocessor box? > > An 8000 and an 8200? > > And HP hasn't mix/matched processor clock frequency's in one box either. > 870 (4-way/PA1.0/CIO) I think had something funny about the clocks which > I think was repeated in the T-class and possible planned in newer > architectures. Can anyone shed more light on this? I think I remember the problem now. The processors can run from a "system clock" and they all run synchronous. No chance of "clock drift" since they run at exactly the same pace. But on systems like 870, T-class and N-class, the processors are fed clock signals from (similar but) different sources. Each frequency domain will slowly drift from the "average" and thus the processor clocks need to be resyncronized regularly. > Minimizing clock drift of the various processors in an SMP box is > a difficult problem. Keeping accurate time is important but > synchronization of processors too often can really hurt performance. grant