The information you are asking about relates to the amount of bit
bandwidth included in the memory pipeline, in short, how much data can
be transferred in one go.
256, is in theory, as the name suggests, twice the bandwidth of 128
bit. This means that when your 128bit GFX card transfers 50 MB of data
the 256 bit card transfers 100MB (so the theory goes).
Deciding on whether to go for 128 bit or 256 bit should be dictated by
your PC usage. Are you going to be a high end gamer? If so opt for the
256 bit. Are you only going to use notepad, word, excel, opt for the
128bit, afterall an 8 MB graphics with windows 98 could probably serve
the purposes there.
These websites will back up what I just said.
http://forums.nvidia.com/lofiversion/index.php?t17268.html
http://forums.whirlpool.net.au/forum-replies-archive.cfm/563865.html
http://www.geocities.com/tnaw_xtennis/NV20-6.htm
When talking about the single 128 bit memory pipe.
"If everyone (even the pro-nVidia reviewers) recognizes that GeForce
is bottlenecked by memory bandwidth, why isn't the solution to go to a
256-bit bus or add a second 128-bit bus (eg: to separate texture data
from T&L data) rather than relying only on DDR and higher RAM speeds
with the single 128-bit bus and unified memory architecture?"
Memory bandwidth is a critical issue when playing graphically intensive games.
To put it into context, I use an Asus GeForce 5900XT with 128 MB
memory with a 256 bit memory pipeline as a game machine graphics card.
I find that I can run most games without much in the way of lag,
however, when it comes to the newer fully fledge bells and whistles
games i have to bring all the settings right down just to make the
game playable.
I'll give you a quite comparison of two cards that are almost the same
with relation to memory speed and GPU speed but one has 128 bit memory
and the other has 256 bit memory.
GeForce FX 5900 XT
GPU 390 MHz
Memory 680 MHz
Memory pipeline 256-bit
Memory throughput 21.7 GB/s
GeForce FX 5700
GPU 425 MHz
Memory 600 MHz
Memory Pipeline 128-bit
Memory throughput 9,6 GB/s
As you can see, the FX 5700 has a faster CPU but slower memory with a
memory pipeline half of the 5900 XT. If you were to equalize the
memory speeds each memory MHZ for the 5700 gives you 16000 throughput
whereas the 5900 gives you 32000 through put.
When you take it all into consideration though, you have to think
about what is most economic for you. The best rule of thumb in IT is
to always buy the best you can afford, as soon as you receive you
hardware it is out of date within 6 months. 256 bit is better than 128
bit by double the factor.
The following is taken from
http://www.hardwaresecrets.com/article/132
If I am to compare the exact models of graphics card you are thinking
of purchasing you get the following.
GeForce 7600 GT
GPU 560MHz
Memory 1.4 GHz
Memory Pipeline 128-bit
Memory throughput 22.4 GB/s
GeForce 7900 GT
GPU 450 MHz
Memory 1.32 GHz
Memory pipeline 256-bit
Memory throughput 42.2 GB/s
As you can see, even with a slower memory clock the 7900 GT is almost
twice as fast as the 7600GT.
The way the games market is currently moving I would say that
purchasing the 7900 GT would make you much happier in the long run
when you compare it to purchasing the 7600GT. The 7900GT has a much
longer shelf life than the 7600GT ever will. Games are getting more
graphically intensive, the 7900GT will be able to cope with this a lot
longer. You also have to realise that the 7900GT can process twice the
amount of pixel per clock tick than the 7600GT can.
At 450MHZ the 7900GT can process 24 pixels per clock tick, which equates to 10800
The 7600 GT at 560 can process only 12 pixels per clock tick, this equates to 6720.
When you factor all this in, on paper the 7900GT card is almost twice
the speed of the 7600GT.
The 7900 GT has more memory, can process almost twice the amount of
information in the same space of time as the 7600, has a greater
bandwidth speed and will certainly be lasting a lot longer than the
7600 ever will.
I would certainly advise the 7900GT over the 7600GT for those who are
looking for games to be played with full AA and shadow details. If you
are not bothered about the quality of your graphics in your games then
the 7600 GT will suffice.
To sum it up, at low end graphics, although the 7900GT will be better
you wont notice much difference, when newer more graphically intensive
games come out that require greater memory bandwidth and and
processing speed you will definitely start noticing a big difference.
I hope this answers your question.
--Keystroke-ga |
