| From: | Aaron Optimizer Digulla |
| Date: | 11 Sep 2000 at 08:37:38 |
| Subject: | PC hardware (Was: AMIOPEN: AmiSame) |
On Wed, Sep 06, 2000 at 07:20:10AM -0500, Rudi Chiarito wrote:
> > Sounds more like a hardware problem to me. Do you have an IDE harddisk
> > set to DMA ? Then check /var/log/messages for errors (my DMA bugs and
> > freezes the machine every now and then).
> Sometimes it's the opposite here. On this machine DMA is not enabled by
> default and transfers are done 16 bits at a time. Whenever a mail arrives
> (through fetchmail/qmail) everything halts: programs crawl, MP3s start
> skipping (no matter if I suid XMMS and enable "realtime" mode), etc.
> Enabling DMA and 32 bit transfers seems to get rid of the problem 99% of
> the times. It's really something that one has to spend time experimenting
> with.
Well, the explanation is quite simple: PC manufacturers are greedy, so they
don't like spending a few cents (which become a few million dollars with
the quantities they sell) on something "when we have a fast CPU which can
do it". What happens is that your fast 32bit CPU (which is optimized
a lot towards 32bit) must poll the harddisk (ie. it will loop until
the harddisk gives it a signal that the data is ready) using 16bit
ops. While it polls, it can't do anything else, so the system "hangs"
or "hickups". The same goes for PS/2 mice (which need about 10-20%
of the CPU while you move them) and some other "cheap" components.
Solution: Save your data and try to enable 32bit mode and DMA. Depending
on whether your DMA controller likes your harddisk (and vice versa),
your system will lockup (mine does seldomly) but if it works, it
will not hickup anymore.
PC hardware is cheap and not inexpensive :-)