-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
Behalf Of Magic
Sent: Wednesday, October 27, 1999 4:06 PM
To: [EMAIL PROTECTED]
Subject: Re: MD: "Hesitating" sound
From: Shawn M. Pierce <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, October 27, 1999 6:29 PM
Subject: RE: MD: "Hesitating" sound
>Throughput means absolutely sod-all I'm afraid. If I had a 32k input buffer
>on a card, and I stuff 32k and 1 byte across the bus, that one byte will
>lock the bus until the card takes it. THe card could be doing anything -
>most likely waiting for the flyback of the monitor to output the next
frame,
>but that bry brief delay would be enough to throw out a device such as a
>sound card. The program misses picking up the sound card interrupt for
>another 64k of DMA and the result is the sound "skips" or "repeats". PCI
>cards access the memory differently, but the principle is the same. If the
>bus is locked, even for a nanosecond too long, the request for more data
may
>be missed. The throughput of your bus could be way in excess of speeds we
>can even imagine but the situation would still be the same. The point is
>that the graphics card IS what locks up system bus lines.
So your telling me that a video card with 2 megs of ram or whatever is
getting 2 megs of data per clock cycle, or maybe around 90 times a second by
using windows? Thats totally illogical since windows requires little in the
way of memory for 2d. Same with soundcards, they too have buffer memory
that can hold prefetch. Thats stupid to think that a modern video card is
held up by monitor inability to keep up, considering monitor refresh rates
are VERY high. The monitor does not accept frames, they accept lines. IE
refresh rates are how many times the monitor redraws a line per second,
starting from top down. And considering that ISA busses and PCI busses are
on different pathways, a video card would not hold up a soundcard, its the
other way around. Thats why when you take out all of your ISA cards, you
get a 5-7% speed increase...I know this because I tried it.
The reason why you get stuttering sound can be for a few reasons.
First, the CPU can be busy because of hard drive activity. When you run an
IDE hdd at full choke, newer ones take up to 40% of the CPU power, older
ones take up even more, upwards of 70%. Add into that CD-roms, and such,
and you get MANY problems. Thats why I use Scsi stuff, a 40x IDE cd-rom
utilizes upwards to 40% CD power, whereas my Plextor 40x UltraScsi uses
around 3%.
MP3 decoding can take up MASSIVE ammounts of CPU power, older versions
of winamp took up more than 30%. Newer versions around around 12-15%.
In Half Life, I had stuttering noises, this was cured by A. Lowering
resolution, why? Not because too much data was going to the video card and
it had to wait to fill buffers, but because too much info was going to the
CPU! That was on my P200, now with my P2-450, I can run the same res, with
the same vid card, same drivers, same OS...and NO STUTTERING!!!
Have you ever looked at the bus scematic for BX chipsets? PCI bus is
on a different bus, the AGP is pretty much on the PCI bus. ISA is on a
different one. Have you ever looked at benchmarks across CPU's? Does the
graphics card scale to the cpu? Or does the CPU scale to the graphics card?
Let me ask you this. If you have a P150 and a GeForce256, will the computer
lock up? HOW CAN IT!?! The graphics card is not getting enough info to it
to fill its frame buffers. However, if you have a p2-600 and a GeForce256,
the CPU STILL cannot feed enough info to the graphics card, because of
polygon throughput...a CPU cannot handle it. This is why graphics cards are
offloading Transform & Lighting from the CPU to the Video cards
(GEForce256's T&L does this).
***************The CPU has to send so much data to the graphics card, that
it has no time to get data to the sound card, hence the
stuttering*************.
If you look at benchmarks, Framerates scale to the power of the CPU up to
a point. That point is the polygon or triangle output of a video card, a
CPU finally is powerfull enough to send enough data to overwhelm a video
card...BUT it does not start stuttering it only tops out at frame rates. I
would say the GEForce256 will top out with a K7-800 or so.
Why can a 386 run Unix as a server? I have one running a small file
server :). Because it is not runing a GUI AND it is not running any
background stuff. Why can ur dos machine decode MP3's? Because its not
running windows wich takes up 50% of system, resources.
Shawn
PS. Who the hell has a 32k video card? Considering vid cards have upwards
of 64 megs of ram now. What fills that much ram? Not windows or winamp
decoding!?!
Shawn M. Pierce
Information and User support specialist
University of Minnesota, College of Agriculture Departments of Plant
Pathology and Agronomy
(612)-301-6034 Day phone
(612)-730-7617 All hours number
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