[PLUG] Why is it slower on a P4?

Derek Loree derek at infotects.com
Tue Nov 19 20:19:33 UTC 2002


On Tue, 2002-11-19 at 11:43, AthlonRob wrote:
> On Tue, 2002-11-19 at 11:16, Derek Loree wrote:
> 
> > I don't see how, with 1Gig of RAM, the DMA state of the harddrive will
> > make the mouse sluggish.  I really can't imagine any swapping going on. 
> > Harddrive speed will affect application startup time, file copies and
> > other read-write activities, but not the mouse movement or general
> > application usage.
> 
> DMA doesn't directly speed up hard disk access so much as it may be
> implied...

DMA66 or DMA100 will be a lot faster than any non-DMA mode.
> 
> DMA reduces the amount of CPU power needed to access the hard drive.
> 
> If you're doing any kind of disk activity, your CPU utilization will
> spike, and that can cause the mouse to jump around like was described.

On any machine running a 500Mhz processor or better, the spike will be
small enough that the mouse should have lots of cycles left for itself.
> 
> In reducing the amount of CPU power used when doing anything with the
> drive, DMA *does* speed up disk access, though.  I would guestimate as
> CPU speeds increase, DMA vs non-DMA in terms of drive speed will become
> less of an issue - but in overall system performance I think it will
> remain relevant.

>From personal experience, DMA mode makes a huge difference (in how fast
apps load and other drive access stuff), whether the processor is a 500,
or a 1300. Mouse behavior did not depend on the drive access mode.

Derek





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