PlanetZ forums - scopeusers.com

Hello all. I have searched the forums on this topic but have yet to zero in on any specific answer. I am setting up a new machine around a Scope project, thinking back to the last time I did this. As I recall, it is important that before the OS even comes into the picture, to make sure that no devices share an IRQ, as reported by the BIOS in the device list printed on bootup. I am finding it impossible to get everything in the list to have a unique IRQ. I have disabled every on-board device possible and have tried every slot combination for the two PCI cards involved (the Pulsar and a mass storage controller). Something called an SMBus controller (whatever that is) likes IRQ 11 and the devices I shove in the slots always seem to grab 7 or 11). There is no apparent way to manually configure IRQs. So, here are my questions:

- was there some trick to forcing unique IRQs (any old kind of trick)?

- in terms of the system, what is the consequence of two devices sharing an IRQ?

- is it OK if the mass storage controller shares an IRQ with someone as long as the Pulsar doesn't?

Any advice would be appreciated. Thanks!

FYI - I believe the mobo is an MSI k7n420, and the mass storage controller is a Promise ATA133.

<font size=-1>[ This Message was edited by: polyestr on 2005-05-18 00:33 ]</font>

<font size=-1>[ This Message was edited by: polyestr on 2005-05-18 00:41 ]</font>

<font size=-1>[ This Message was edited by: polyestr on 2005-05-18 01:35 ]</font>

<font size=-1>[ This Message was edited by: polyestr on 2005-05-18 01:37 ]</font>

<font size=-1>[ This Message was edited by: polyestr on 2005-05-18 01:38 ]</font>

you should be ok if the pulsar doesn't share. sharing is only a problem if both devices need the bus at the same time. the controller you mentioned should be fine. install the os and see what happens. if you have problems, then you can reconfigure/change slots. upon restart the irqs will be reassigned.

btw- if that's a raid controller, you really don't need raid. you can remove/disable raid and just use ide. a 7200 rpm ide drive is plenty fast.

<font size=-1>[ This Message was edited by: garyb on 2005-05-18 02:37 ]</font>

It is a non-RAID IDE controller, and unfortunately it can't be eliminated from the mix. What is an SMBus controller and why wouldn't it need the bus (I assume you're talking about the PCI bus) at the same time as the IDE controller, if the two were to share an IRQ? I certainly don't need the system waiting any longer than it has to to perform I/O, even if it is stable.

<font size=-1>[ This Message was edited by: polyestr on 2005-05-18 10:40 ]</font>

you should be fine.
here's some gobblety-gook from a google search:

System Management Bus (SMBus 2.0)
The ICH4 contains an SMBus Host interface that allows the processor to communicate with SMBus slaves. This interface is compatible with most I²C devices. Special I²C commands are implemented.

The ICH4's SMBus host controller provides a mechanism for the processor to initiate communications with SMBus peripherals (slaves). Also, the ICH4 supports slave functionality, including the Host Notify protocol. Hence, the host controller supports eight command protocols of Quick Command, Send Byte, Receive Byte, Write Byte/Word, Read Byte/Word, Process Call, Block Read/Write, and Host Notify.

basically it's for peripherals control. there's bound to be some sharing with all the devices on a modern motherboard and i would bet that your mobos manufacturer expected that. i wouldn't worry unless you have a specific problem. neither of the devices that you have sharing require the resources that the pulsar card does. i have similar sharing with no adverse effects. just keep the cwa card to it's own irq and you should be good.

Ok I'll take your word for it then and move my focus toward the OS. I would be more comfortable if something other than the disks were sharing that IRQ, since this machine will be used as a sampler and consistent high disk performance will be necessary. But it's either that or the Pulsar, and it ain't gonna be the Pulsar. Damn! Oh well, thanks man.