Date: Tue, 17 Dec 1996 18:51:21 -0700 (MST) From: Steve Passe <smp@ilsa.systemsix.com> To: freebsd-smp@freebsd.org Subject: Re: AMI Merlin DP Motherboard Message-ID: <199612180151.SAA15012@ilsa.systemsix.com>
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>Would you caution against the purchase of any MP EISA board or just P6? any, the EISA issues are unrelated to P5/P6 stuff (kinda, this is complex) Some EISA systems do not connect the system clock (8254) to the IO APIC.This requires "mixed-mode" programming the IO APIC AND the 8259 ICU. I have already written the code to do this and it appears to work. BUT this is a small in-efficiency for hard-clock INTs. So far ALL EISA systems I have seen use the ISA INTs 0-15 redirection capability for routing both EISA AND PCI INTs to the lower 16 ISA INT vectors. some (majority, but NOT all) PCI/ISA systems route the PCI INTs to upper (ie above 16) IO APIC INTs, thus giving you 4 or more extra INT vectors, helping greatly with the typical "not enough INT choices" on the ISA bus. this fact is the major reason I have for avoiding EISA boards. you need to go thru the mptable database to see details about what I am talking about here. >Do these motherboards cause the same problems with other (Sun, SCO) SMP implementations? The issue is "Intel MP spec motherboards". this means among other things ONLY Intel CPU's (P5/P6). In otherwords its strictly a hardware issue, NOT an OS issue.
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