Subject: Re: Processor upgrade card.
From: Timothy A. Seufert (tas@mindspring.com)
Date: Thu Dec 20 2001 - 17:47:04 MST
At 3:29 PM -0800 12/20/01, Martin F. Melhus wrote:
>I have a 7600 with a Sonnet Crescendo G3/400 processor upgrade
>card in it. YDL doesn't seem to see the full capacity of the
>card; the system info gizmo informs me that it is running a
>195 MHz G3, which is exactly the same number that the Mac end
>reports if I don't use the Sonnet Accelerator Extension on
>boot-up.
>
>Anyone have any expertise with this? Can I use the full
>power of the fast processor. And yes, I know, YDL for old
>macs is about taking slow machines and making them useful.
>I still have my 233 MHz 604e card, but I'd rather use the
>G3.
>
>When I was running LinuxPPC, there was a huge speed boost
>when I switched from the 604e to the G3. I speculate that
>something in LinuxPPC 2000 picked up the fact that it was
>a 400 MHz G3, and let it run all out. YDL doesn't seem to
>be as fast as it could be - any input on this?
Yes. You are worrying about something that means nothing -- the
system info gizmo you are using is wrong. On PowerMacs like your
7600, the OS _cannot_ reduce the CPU's clock speed, because the speed
is set by hardware on the CPU daughtercard.
It's probably getting 195 MHz from /proc/cpuinfo (do "cat
/proc/cpuinfo" at a command prompt to see it yourself). The
information there about clock speed is not necessarily true because
it's not based on reading hardware. It's merely repeating
information given to the Linux kernel by Open Firmware. The Open
Firmware in the 7600 is somewhat buggy, and one of the bugs is that
it often reports 195 MHz if the CPU is anything but the factory
original CPU, regardless of what speed the upgraded CPU is actually
running at.
What you do need to worry about is whether your G3's L2 cache is
enabled. Not only is the 7600's firmware buggy, it hasn't got a clue
about how to enable the G3 L2 cache (unlike computers which came with
a G3 from the factory).
To check whether Linux is running with the cache disabled, open a
terminal and type "cat /proc/sys/kernel/l2cr". The output should
look something like this:
0xb9914000: enabled, no parity, 1MB, +2 clock, pipelined burst SRAM,
ZZ enabled, copy-back, 1.0ns hold, diff clock
If the first English word is not "enabled", your cache is not enabled
and the system will be slower than it ought to be. You're probably
using BootX to boot Linux. Its documentation should have information
on how to get the L2 cache configured right under Linux on a Mac with
a G3 upgrade.
-- Tim Seufert
This archive was generated by hypermail 2a24 : Thu Dec 20 2001 - 18:01:00 MST