Re: 2.6.15-1-sparc64 issues on blade 100
On Feb 14, 2006, at 11:42 AM, Dave Love wrote:
My XF86Config-4 does still have the old
Option "reference_clock" "28.636 Mhz"
though. Presumably that should be irrelevant now, should it?
Dave:
I've been dragging that line around in my X config file for
quite awhile. So I decided to run an experiment this morning and see
what happened if I deleted it. Lo and behold, I got diagonal stripes
moving up (or down) quickly, as if the VHOLD and HSYNC on an old TV got
played with by a 4 year old nephew. Buried in the X log was the
following
line:
(--) ATI(0): Reference clock 14.318 MHz.
Now this number was familiar; I had just seen it on web page
describing the
options for the ATI driver for Xfree:
http://www.xfree86.org/~dawes/4.3.0/ati5.html#26
But the number 28.636 still seemed funny, it was mentioned in the web
page as a typical
value, but when I took the cover off of my Blade 100 to check on the
clock frequency
that the kernel ATY FB driver needed, I did not recall seeing that
clock frequency there.
So I took a peek at the reference clock chip (X7) and it is a 29.4
Mhz clock.
So I would say:
1) An 'Option "reference_clock" "XXX Mhz"' line is needed as the X
driver sets the reference clock to a default value when a PC BIOS is
not present.
The default is wrong for my machine and is likely wrong for all
Blade 100's.
2) At least some SPARC Blade 100's have a 29.4 Mhz reference clock.
3) The difference between 28.636 and 29.4 Mhz is small enough to be
ignored
for large divisors, but could present a problem for small divisors.
4) It could be that no Blade 100 uses a 28.636 Mhz reference clock
and that
someone tried the next "typical" value on the list and stopped
experimenting
since it worked and never took the lid off to see if the value
reflected what
the hardware was doing.
Can any other owners of SPARC Blade 100's out there pop the lid off
their machines and
look at numbers printed on the two clock crystals near the RageXL
chip? On my machine,
the crystal is labeled X7.
-- Luis
PS: If you need a picture, I have one I can send you if you need it.
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