Date: Wed, 23 Jul 1997 22:22:55 -0800 From: Chris Browning <brownie@earthling.net> To: freebsd-smp@FreeBSD.ORG Subject: Re: Lots 'o PCI slots Message-ID: <33D6F4BF.3FF44FA1@earthling.net> References: <199707231856.MAA16991@Ilsa.StevesCafe.com>
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All, I think this is a very interesting topic for FreeBSD to look at. I have been thinking about getting some of the free Un*xes to support I2O. There are many advantages to using it. 1) OS & Adapter drivers are separated. Now, you only need to write an OS driver the interfaces to an abstract devices, like a "SCSI controller" or a "NIC". The device specific stuff is all handled by a OS independent adaptor driver. Therefore, you would only need to have a couple of drivers to support all adapter cards that support I20 can then be used with the OS. 2) The IOP (I/O Platform) handles interrupts & servicing the devices it supports. This reduces the overhead that the OS & host platform must spend servicing I/O request and leaves them more time to do computations, etc. 3) Peer, Device-to-device transfers are possible. A SCSI adapter can copy a file out to the network without the main CPUs even being interrupted. It is all handled by the IOP. Well, that is a short plop about I2O > I'm ignorant of the I2O/i960 hardware setup, but I believe the i960 > has an > onboard APIC interrupt controller. Do such motherboards require the > use > of the APICs to handle the concept of driver offloading? If so, as > the person > writing most of the SMP APIC code, it might be a good idea for me to > find > out more so that I can consider this issue when making arch. > decisions... Well, I just thumbed through the I2O spec, and it made no mention of APICs or even much about how interrupts with the host system are handled. I am guessing that this is implementation specific. If I find out anything more that I can tell you, I'll let you know. Hmm, I wonder if I were to write a I20 driver for Linux or FreeBSD would anyone get upset (I think all Intel employees are I20 SIG members :-) Chris Not speaking for anyone, especially Intel.
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