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Having trouble installing a piece of hardware? Want to know if that peripheral is compatible with Linux?
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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.
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?
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).
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.
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".
"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.
"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.
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