Re: sym53c875E-0: PCI clock seems too high

Gerard Roudier (groudier@club-internet.fr)
Sat, 25 Sep 1999 23:08:26 +0200 (MET DST)


The test of the PCI clock is not intended to prevent user from stupidly
breaking their hardware, but some reality test to prevent the driver from
being wrong about its estimation of the SCSI clock of the chip. Applying
the algorithm to the PCI bus and checking the result against the expected
reality (33Mhz), allows to make sure the algorithm is correct. This
algorithm is based on the udelay() stuff of Linux that sometimes may give
weird results, especially on new hardware, and then break the driver
calculation of the SCSI clock.

I will NOT remove the reality test of the PCI clock, but allow user to
tell the driver about the reality they choose for the PCI clock frequency.
This will be a boot command option that will be defaulted to 33 MHz.
Probably something like : pciclk=41 to inform the driver about the PCI BUS
being clocked to 41 MHz.

I actually donnot care of people who overclock their hardware. I just ask
them for not wasting our time with problems due to their decision to
overclock. These people must know that hardware that have been overclocked
can be definitely damaged and experience far more error than specs said.

Overcloking a CPU that is in fact sold with an underclocked specification
is one thing. Overclocking a BUS and then everything that connect to it by
more than 10% was not imaginable by me. By the way, I think that people
that overclock PCI 33 Mhz buses up to 41MHz or more are just foolish and
plain idiot, but I don't care of them.

Gérard.

On Sat, 25 Sep 1999, Mr. James W. Laferriere wrote:

>
> Hello Paul,
>
> On Sat, 25 Sep 1999, Paul Flinders wrote:
> > Mr. James W. Laferriere writes (upside down):
> > > On 25 Sep 1999, Paul Flinders wrote:
> > > > I get this from the Symbios 53c8xx driver in 2.3.18ac8
> > > > sym53c875E-0: PCI clock seems too high (37662 KHz).
> > > > The bus speed *is* correct as the motherboard is overclocked - I know
> > > > not everyone approves and I'm prepared to take the consequenses.
> > > > However, if the check was not specifically intended to prevent the
> > > > driver working on overclocked boards could I suggest changing the
> > > > comparison from 37Mhz to 42Mhz.
>
> > > Hello All , I beleive that a manually setable comparison
> > > which overrides the default value for those willing to
> > > experiment with Higher clock speeds . .02 JimL
>
> > If it's just a sanity check then it's probably reasonable to make it
> ^^^^^^^^^^^^^^^^^^^ Then why does it (presumably) prevent
> people from using there equipment . Otherwise there is no
> point in making alot of noise over a simple message .
> I still beleive that a manually setable value s/b available,
> ie: at boot: or lilo.conf/... time . If it prevents usage .
>
> > 42Mhz (83/2 being 41.5). Some boards do 133 but leave the PCI bus at
> > FSB/3 (i.e 44) but I doubt any system will run like that. It may even
> > be worth adding a check that it's over 25Mhz.
> Spewing a message about it is OK .
>
> > If it's intended to warn/stop overclockers then it should need the
> > code to be manually changed.
> Why, Not all those overclockers are kernel hackers they may be
> hardware geeks . Not everyone in the world knows kernel level
> hacking & not everyone who is a kernel hacker knows -every-
> idiosyncracy of hardware .
> Twyl, JimL
> +-----------------------------------------------------------------+
> | James W. Laferriere | System Techniques | Give me VMS |
> | Network Engineer | 25416 22nd So | Give me Linux |
> | babydr@baby-dragons.com | DesMoines WA 98198 | only on AXP |
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>
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