[vbox-dev] ICH9 devices

Michal Necasek michal.necasek at oracle.com
Wed Jan 6 21:22:15 UTC 2016

There's no architected way to disable the bridges or the LPC device because no user needs to do it. You could probably do it by modifying the source code. 

You should be able to disable network and USB. Beyond that you will have trouble booting anything. 

I can only repeat again that I know of no reason why the ICH9 chipset should be significantly slower or faster than the default chipset. If you think there is extra code being executed, you should be able to find it with a debugger or a profiler. I can't help you because I never heard of such behavior. 

Did you compare the exact same VM where only the chipset was different? Or are you comparing VMs that aren't really otherwise identical? 


----- Original Message ----- 
From: apallapothu at gmail.com 
To: michal.necasek at oracle.com 
Cc: vbox-dev at virtualbox.org 
Sent: Wednesday, January 6, 2016 12:04:54 AM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna 
Subject: Re: [vbox-dev] ICH9 devices 

Right, AHCI isn't behind bridge, I misread. 

I certainly need network and disk. 

Devices I see in my ICH9, VGA-CustomPassThrough, VGA, E1000, VMMDev, ACPI, LPC, ich9pcibridge 1, ich9pcibridge 2, AHCI, USB-OHCI 

Can I disable LPC, 2 bridges ? I can't seem to find the commands in user manual though. 

I am thinking slowness can be because CPU has to execute more instructions coming from "other extra" devices in ICH9 but when I am fairly using same setup, drivers as I used on PIIX3 ... not sure why ICH9 would take longer which infact we expect it to be faster. Please comment. 


On Fri, Jan 1, 2016 at 1:04 PM, Michal Necasek < michal.necasek at oracle.com > wrote: 

Not sure what you're referring to. Your driver specifically? Or the entire guest OS? In general, there is not known to be any significant performance difference between the chipsets either way. Specific devices might perform faster with ICH9 (e.g. xHCI with MSIs is faster than xHCI without) but the difference isn't huge. 

If it's your driver specifically then... well, why is it behaving so differently? Only you can find out. 

Most of the devices aren't "required" as far as VirtualBox is concerned, but there's only so far you can get without disk or network. 

FYI, in my VM, AHCI definitely isn't behind a bridge. It's at bus/dev/fn 0:1f:02. 

- Michal 

----- Original Message ----- 
From: apallapothu at gmail.com 
To: vbox-dev at virtualbox.org 
Sent: Thursday, December 31, 2015 2:52:49 AM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna 
Subject: [vbox-dev] ICH9 devices 

Hello Experts, 

My "custom" driver execution takes long with ICH9 as compared to PIIX3, ~4X difference. Custom device is a pluggable device registered. 
Apart from 2 "ich9pcibridge" devices I don't see any thing else "new" in ICH9. 
With ICH9, AHCI is connected on other side of the bridge (on bus 2), while on PIIX3, it is on the root port. Could this be the reason for slowness ? 
I used same settings between the two chipsets, have disabled "audio" in both instances since I don't need them. Is there a way to reduce overall traffic ? 
I presume all current devices in ICH9 are required (?) but is there a way to improve performance ? I am not much bothered about other devices, apart from having functional chipset. 

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