reduce interrupt rate for CD/DVD drive(r)

[Jin Guojun [VFFS]]

I have difficulty to get CD/DVD write speed above 1.6MB/s  (10x for CD, 
or 1.1x for DVD).
The problem seems to be the interrupt rate is high (70-80% of CPU) for 
CD/DVD drive(r).

I have tried three different CD/DVD drives under three different 
hardware platform
with FreeBSD 4.11-R/6.1-R via growisofs, cdrecord, and burncd programs, 
and all
combinations had the similar results. Non of them can go beyond the 1.6 
MB/s writing
speed.

The reading speed is also far away from the manufactory specification due to
high interrupt rate.

Is any way to reduce the interrupt rate in order to increase the CD/DVD I/O
performance? or is anything else to tune the performance?
I doubt this is the hardware issue, but if this is possible, please 
point it out.

Thanks,

    -Jin

P.S.:    Below is the information for systems have been tested --

Systems (FreeBSD4.11/6.1 i386):
AMD XP 2100+ (1.667GHz)
Intel P4 3.0GHz

plus one of these CD/DVD drives:
Micro Advantage CD-RW    IDE-52-32   (52x read, 32x write on CD-RW media)
Sony DRX-510UL CD/DVD-RW   USB/1394   (2.4x DVD+RW, 4x high-speed DVD+RW)

(FreeBSD-6.1 i386/amd64)
AMD Turion 64 ML-34 (1.8GHz) + HP double layer 8x DVD+-R/RW Super Multi 
drive

CD/DVD media:
48x CD-R, 52x CD-R (from manufactory), 12x high-speed CD-RW, 2x DVD-R, 
4x DVD+RW