As far as I know, that is true and you don't need a SCSI controller
(or any other PCI card) for a ISA card to be handled with low priority.
The IDE controller, for example, can take all the bus cycles if not
properly configured and if used at full load.
The parameter you have to worry about is called "latency" and roughly
it defines how many cycles a PCI card holds the bus before it releases
it again to another PCI card (or ISA for what that matters).
Guilherme
>Date: Wed, 20 Oct 1999 11:41:18 -0700
>From: "Garth Gaddy" <[EMAIL PROTECTED]>
>Subject: [rtl] RTL or RTAI: Determinism while using SCSI Raid
>
>I am doing 4 axis servo control w/ an ISA servo interface board and RTLinux.
This will eventually find it way into a machine that needs maximum uptime
possible. Therefore I would like to use a SCSI Raid controller with Hot-swap
drives.
>I have been warned that the Raid controller, a pci bus master card, will take
priority over any ISA device and therefore I might not be able to maintain
determinism of 1khz ISR on the interface card.
>Does anyone know if this is true?
>
>Secondly I have looked into a similar card in PCI form from Acromag. I can
configure what interrupt I want it to generate, typically IRQ 5.
>Does anyone know how the interrupt controller resolves the SCSI Raid card and
the PCI Servo card's respective interrupts?
>Is there a way to set up interrupt prioritization so that the Servo card has
preemptive priority?
>
>Thanks in advance,
>
>Garth Gaddy
>
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