Anyone *PLEASE* help me with this?!

I guess it's not a common problem, but if anyone of the Linux-Gurus out here
could *ACTIVELY* help me dig up a solution for this..?? I bet you at least have
*some* idea where to begin searching and how to approach this; 'cause I - being
quite a Noob when it comes to Linux administration - simply don't. Tried to
google for it but didn't get a clue (at least none that I could understand).

So here's the issue:

I've set aside a brand-new AMD QuadCore with Debian Linux and MegaPOV for
rendering purposes; everything seemed to be fine, and I even managed somehow to
configure Gnome and set up Xming and Samba so I can access the box from my
everyday-work Windows machine quite comfortably.

Now I notice that the Linux system timer is running WAY TOO FAST, about twice
the regular speed. I set the clock at ~19:45; at 20:20 it showed 20:58, and at
20:43 it is showing 21:44 presently.

Maybe related to this is an effect I see in "top", which reports MegaPOV tasks
as taking up quite precisely 50% of cpu time each (Gnome's System Monitor
correctly reports them as using 25% though, corresponding to one core).

I gather that there's a problem on AMD machines with *some* way Linux keeps
tracking time ("TSC"), while there's another way that should work (two actually,
"PMtimer" and "HPET").

I don't get the slightest clue, however, what I should do in order to fix this
in Debian Linux (or any other Linux, for that matter) to make my system keep the
correct time.

I just want to run MegaPOV on that computer (and maybe POV 3.6 and later 3.7). I
also don't actually care what Linux distribution I'm running as long as it
works, so recommendations for a (freely downloadable) distribution that
will run "out of the box" on my system would be welcome, too.

I'm running an AMD Phenom X4 9650 2.3 GHz on a Gigabyte MA78GM-S2H mainboard
with 4GB of RAM.

*ANY* help appreciated, provided it is Linix-Noob-compatible. I think I need
someone to navigate me through whatever solution there may be, step by step.

Post a reply to this message

On Wed, 10 Dec 2008 14:47:12 -0500, clipka wrote:

> Now I notice that the Linux system timer is running WAY TOO FAST, about
> twice the regular speed. I set the clock at ~19:45; at 20:20 it showed
> 20:58, and at 20:43 it is showing 21:44 presently.

With or without MegaPOV running?

If with, you may want to ask in the Debian community, as there will be 
many more people who have experience with this sort of issue in the 
kernel.

I've seen this myself in VMware VMs with a laptop using Intel Speedstep - 
it's been a few versions since this was a problem, but I've never seen it 
in a native kernel installation.

Jim

Post a reply to this message

Jim Henderson <nos### [at] nospamcom> wrote:
> On Wed, 10 Dec 2008 14:47:12 -0500, clipka wrote:
>
> > Now I notice that the Linux system timer is running WAY TOO FAST, about
> > twice the regular speed. I set the clock at ~19:45; at 20:20 it showed
> > 20:58, and at 20:43 it is showing 21:44 presently.
>
> With or without MegaPOV running?

Both.

To quickly asses how I'm doing regarding this, I set the Gnome clock to display
the time in unix timestamp format, so I can see it counting seconds.

Processor load does not seem to have any influence on this. Time seems to be
flying constantly at 200%.

I toyed around with BIOS settings and boot parameters a bit, only to find out
that "notsc" doesn't help a thing, and disabling the HPET in the BIOS was just
as futile.

Only thing I could find out was that it is in fact multi-processor related, as
"nosmp" gets the counter down to normal speed.


I also found out that Knoppix does fine with default settings. But then again, I
don't know whether it does SMP.

Post a reply to this message

Follow the following steps:

1) Make a bug report to the Debian community.

2) If the bug is not fixed soon, remove Debian and try another distro. Maybe
   it's a bug specific to Debian. I myself use OpenSUSE, and it's cool.
   (I don't have a quadcore system, though.)

-- 
                                                          - Warp

Post a reply to this message

Hi !

The first thing to do is to reboot the machine and go in the BIOS.
Then set the clock correctly, save and shutdown the machine.
Wait for couple of minutes (15 - 30 minutes) and turn it on againt.
Go in the BIOS and check the time.

If time as gone twice as when running linux, shutdown the machine, 
remove your motherboard and send it back to your resealer.

If not, you'll have to tweak kernel options manually.

Post a reply to this message

Thierry CHARLES <thierry@_no_spam_les-charles.net> wrote:
> The first thing to do is to reboot the machine and go in the BIOS.
> Then set the clock correctly, save and shutdown the machine.
> Wait for couple of minutes (15 - 30 minutes) and turn it on againt.
> Go in the BIOS and check the time.

Hey, I may have no idea how to administer a Linux system, but I do know how to
tell a faulty RTC from an OS getting its own timekeeping wrong...

> If time as gone twice as when running linux, shutdown the machine,
> remove your motherboard and send it back to your resealer.
>
> If not, you'll have to tweak kernel options manually.

That was exactly where I was hoping some Linux Guru who might be experienced
enough to google this problem up in no time flat could go out of his way and
help me: HOW to tweak the damn system, and WHAT to tweak.

I was actually hoping for something more substantial than the usual "RTFM" type
of replies - that someone might be willing to invest maybe 15 minutes to save
me from spending half a day trying to dig up the very same information myself.


Well, I *did* dig it up by myself now, and I'm glad it took me "only" 3 and a
half hours spent on nothing but this single problem...

.... or was it 7 hours? I guess it depends on the frame of reference in this
case...

Anyway, sorry for letting off steam on you. I'm just very, very, *very* upset at
the moment, about how really, really, *really* badly open source stuff tends to
be documented, how many promising internet links lead to nowhere, how
distribution producers leave all the documentation and support to "the
community", and a lot more.

The solution? Just add a bloody "no_timer_check" at the right place in the right
file (actually it's the kernel boot options in the Grub boot loader settings, as
I have learned today). Documentation? Well, seems to be one of those occult
secrets circulated in "the community".

So I don't know what exactly that thing might do, and how it could possibly
wreck my system as a side effect - but at least the clock seems to run properly
now...

Post a reply to this message

On Wed, 10 Dec 2008 16:33:39 -0500, clipka wrote:

> Both.

Then it's unlikely to be a POV-Ray or MegaPOV issue - so definitely I'd 
suggest talking to some Linux kernel folks - you're likely to find much 
more in-depth knowledge in that community.

Jim

Post a reply to this message

On Wed, 10 Dec 2008 23:05:20 +0100, Thierry CHARLES wrote:

> If not, you'll have to tweak kernel options manually.

This *should* be unnecessary, though.

Jim

Post a reply to this message

.... "top" now prints meaningful stats for the processes now, too (although it
gives CPU usage in % of a single core, not the whole CPU as the Gnome System
Monitor does).

Post a reply to this message

On Wed, 10 Dec 2008 17:44:59 -0500, clipka wrote:

> That was exactly where I was hoping some Linux Guru who might be
> experienced enough to google this problem up in no time flat could go
> out of his way and help me: HOW to tweak the damn system, and WHAT to
> tweak.

I don't know that it takes a Linux guru, but here you go:

http://letmegooglethatforyou.com/?q=debian+clock+runs+fast

Try the third result, looked promising to me. :-)

Jim

Post a reply to this message