[plug] Burning DVD's Drifts Time

[Timothy White]

I think the issues has something to do with high interrupts. When I
burn DVD's, my clock starts to slow down. And when I say slow down, I
mean it looses 30 seconds a minute. (So a minute in the computer
world, is a minute and 1/2 in the real world). Also, when I type, I
occasionally get double or triple characters even when I'm typing
normal, suggesting keyboard interrupts are being delayed. (II debated
leaving all the doubles and triples in so you can get an idea of how
annoyinggg it is!)

I've been burning 40 DVD's from a master image, and at the start, I
could get 8x burning speed (16x cheap media), but now, I've not been
able to get above 4x as the initial start speed, which averages 2x
actually burning speed.

The computer is an Athlon64 3000+, with plenty of memory (1 Gb), and
the DVD burner is on it's own IDE bus, as the master of the second
channel. All on it's lonesome. I have 2 HDD's on the master bus, and
2 on the SATA bus. The DVD master image is on one of the SATA drives.

Reading off the SATA drives isn't a problem or bottleneck.
$ hdparm -tT /dev/sda

/dev/sda:
 Timing cached reads:   3968 MB in  2.00 seconds = 1982.95 MB/sec
 Timing buffered disk reads:  162 MB in  3.01 seconds =  53.85 MB/sec
$ hdparm -tT /dev/sdb

/dev/sdb:
 Timing cached reads:   3956 MB in  2.00 seconds = 1978.60 MB/sec
 Timing buffered disk reads:  190 MB in  3.01 seconds =  63.03 MB/sec

Memory isn't an issue

$ free -m
             total       used       free     shared    buffers     cached
Mem:          1001        988         13          0          6        480
-/+ buffers/cache:        501        500
Swap:         4009          0       4008

To give you an idea of the drift, at "1 second intervals" running
ntpdate against a local time server, you can see when the DVD finished
burning.

5 Nov 07:17:24 ntpdate[8651]: step time server 192.168.0.1 offset 0.663251 sec
  5 Nov 07:17:26 ntpdate[8653]: step time server 192.168.0.1 offset 0.551902 sec
  5 Nov 07:17:27 ntpdate[8655]: adjust time server 192.168.0.1 offset
0.455908 sec
  5 Nov 07:17:29 ntpdate[8657]: step time server 192.168.0.1 offset 0.859248 sec
  5 Nov 07:17:30 ntpdate[8659]: adjust time server 192.168.0.1 offset
0.483909 sec
  5 Nov 07:17:32 ntpdate[8661]: step time server 192.168.0.1 offset 0.883246 sec
  5 Nov 07:17:33 ntpdate[8663]: adjust time server 192.168.0.1 offset
-0.000085 sec
  5 Nov 07:17:34 ntpdate[8665]: adjust time server 192.168.0.1 offset
-0.000049 sec
  5 Nov 07:17:35 ntpdate[8667]: adjust time server 192.168.0.1 offset
-0.000074 sec
  5 Nov 07:17:36 ntpdate[8669]: adjust time server 192.168.0.1 offset
-0.000052 sec

$ uname -a
Linux linjeni 2.6.18linjeni #3 SMP Wed Sep 27 21:13:32 WST 2006 x86_64 GNU/Linux

So what I'm really asking, is firstly does anyone know how to stop the
clock drifting during high interrupt periods (i.e. burning DVD's). ntp
normally keeps it in sync fairly well once the DVD stops burning, but
when doing 40 in a row, your quickly  more than a hour out!

Also, does anyone have ideas to get it burning quicker. It was going
at 8x, no idea why real speed isn't getting above 2x now :( It's made
for a really long weekend.

Thanks

Tim
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Linux Counter user #273956
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