how to set system bus speed?

wayback · 01-07-2004, 01:14 AM

I've just installed a new distribution (slackware). One of the boot-up messages is:
"ide: Assuming 33 Mhz system bus speed for PIO modes; override with idebus=xx". It seems like this needs to be changed (not sure what "PIO modes" are though), but how? Haven't been able to find where idebus can be set.

Quis · 01-07-2004, 06:09 AM

(on linux-2.4) you can set idebus with idebus=66 as a kernel-paramter (in your bootloader config the same like hdd=ide-scsi) on bootup.

dalek · 01-07-2004, 06:33 AM

But what does it run at by default? I read dmesg and it says 33MHz. This thing is capable of 133MHz. So which does it run at?

I'm curious now?????

itsme86 · 01-07-2004, 09:50 AM

If it says it's assuming 33MHz then it's running at 33MHz. Edit /etc/lilo.conf and add a line near the top (the global section) that says: append="idebus=133"

Then re-run lilo.

wayback · 01-07-2004, 04:43 PM

I tried this and unfortunately it had no effect, still get the same message during boot. Tried both in the global section and the image section of lilo.conf, and setting to either 66 or 100. Any other ideas about how to set this?

wayback · 01-07-2004, 04:52 PM

Oops, correction - it does work, it just has to go in the image section (i.e. for a particular kernel) of lilo.conf, not the global section - I forgot to re-run lilo after the first try (in the global section).

Thanks for the help!

dalek · 01-07-2004, 07:19 PM

Crap, I have five days of up time. Now I have to reboot.

<deep sigh>

Wonder if this will help those hdparm timings?

I'll post later and see.

Later

wayback · 01-07-2004, 07:59 PM

One other thing, it won't accept a 3-digit number, so you can't set "idebus=100" for example (it will be ignored). Perhaps the driver needs a new revision? Seems like maybe a lot of linux users with newer boxes aren't getting optimal performance currently.

Also I'm not certain that it won't work in the global section, I may have been using =100 when I tried that. But I know it works in the image section.

dalek · 01-07-2004, 08:31 PM

Well this is what I have in my Grub file.

title Gentoo
kernel (hd0,0)/bzImage.test3 root=/dev/hda9 acpi=off hdc=ide-scsi idebus=66 ide0=ata66

The last bit was suggested in dmesg so I tried it. The hdparm timings are the same, but it seems to be a bit faster, not sure though.

When I tried ide=133 it said it didn't like it and went back to 33. I bought a 133 bus mobo and hard drive and can't use it?

Confused. I'm on a mission now. Gone google(ing).

Later

wayback · 01-07-2004, 08:54 PM

Yes I just discovered that what finally seems to work on mine is "idebus=ata66" or "idebus=ata100" (i.e. it does not produce any error message during boot-up, haven't looked at disk timings) -- whereas using "idebus=66" does generates an error message that says it can't set it to 66000 (!) so it will use ata66. So maybe you should try "idebus=ata133".

dalek · 01-07-2004, 09:51 PM

Been googleing but most of what I find is dmesg for other problems.

Going to try that idebus=ata133 and see what happens.

Right back.

dalek · 01-07-2004, 10:00 PM

Well this is what I get.

ide_setup: idebus=ata133 -- BAD OPTION

I don't think it liked it. It does like the idebus=66 though.

I just wonder what the ide0=ata66 is suposed to mean.

Gone google(ing) again.

Later

dalek · 01-07-2004, 10:21 PM

I found this on a site.

Code:

"idebus=xx"		: inform IDE driver of VESA/PCI bus speed in Mhz,
				where "xx" is between 20 and 66 inclusive,
				used when tuning chipset PIO modes.
				For PCI bus, 25 is correct for a P75 system,
				30 is correct for P90,P120,P180 systems,
				and 33 is used for P100,P133,P166 systems.
				If in doubt, use idebus=33 for PCI.
				As for VLB, it is safest to not specify it.
				Bigger values are safer than smaller ones.

Sounds like 66 is the biggest. What gives?

Also found this.

Code:

"idex=autotune"	: driver will attempt to tune interface speed
				to the fastest PIO mode supported,
				for all drives on this interface.
				Not fully supported by all chipset types,
				and quite likely to cause trouble with
				older/odd IDE drives.

Still looking

UnTamed · 01-07-2004, 10:38 PM

idebus speed is not the FSB. it's the speed the ide controller runs off the pci bus.
Common modern day desktop with 32 bit pci run @ 33mhz.

High-end server boards with 64 bit pci 2.0 support run their bus @ 66 mhz [...66000hz ...!],
so unless you got one of those, I wouldn't bother.
Besides, thats just to set PIO speed while you all probably use DMA

dalek · 01-07-2004, 10:50 PM

Yeh found this little tid bit of info way down in dmesg:

Code:

hda: 156301488 sectors (80026 MB) w/2048KiB Cache, CHS=16383/255/63, UDMA(100)
 /dev/ide/host0/bus0/target0/lun0: p1 p2 < p5 p6 p7 p8 p9 p10 >
hdb: max request size: 128KiB
hdb: 60058656 sectors (30750 MB) w/2048KiB Cache, CHS=59582/16/63, UDMA(133)
 /dev/ide/host0/bus0/target1/lun0: p1 p2 < p5 >

Now my NEW 80GB drive is supposed to be 133 too. Now what?

Later

Google(ing) again