Blinker said:
And what is difference between 128-bit DDR or 64-bit DDR?
thanks.
Most of the differentiation in video cards, has to do with
their prowess in 3D games.
Take an example.
http://www.gpureview.com/Radeon-HD-2400-Pro-PCI-card-561.html
Max Power Draw: 25 W
This will likely not be a problem for a 250W supply. The card
would be using 10% of the power supply's max power. It is possible
to compute a guesstimate for the internal consumption of the
computer, but I don't expect this to be a problem.
Framebuffer: 256,512 MB
This memory is used to hold rendered frames, and could use
double or triple buffering. Most of the memory is used to
hold Textures for games. 128MB is the bare minimum right
now, in terms of compatibility with current and future
OSes, such as Vista (Aero) or Windows 7. If you aren't a
gamer, either of the above sizes would be fine.
The memory types range from DDR to GDDR5. The advantage of
the latest memory types, is higher speed and lower power
consumption. I believe I/O power on the memory chips dropped
a bit, with some of the latest ones.
Memory Bus Type: 32x2 (64 bit)
This is the width of the memory bus, which connects the memory
chips to the GPU chip. 64 bits is currently the minimum. I think
it might go as wide as a 512 bit bus on high end cards. This sets
the memory bandwidth. Memory clock * bus_width = Max_memory_bandwidth.
Video cards carry out more than one memory transaction at a time.
The memory is split into independent banks. So for example, the
GPU can send four different addresses to four independent banks
of memory, and get back four bursts in response. The memory is
typically not operated now as a single bank.
People use this as a metric, for the card's purpose. A 64 bit wide
card is a non-gamer card. Something at 256, 384, 512 bits wide might
be gamer material. The clock rate of speed is also important. Note
that, in some cases where eight different companies make the same card,
the performance of the memory actually spans about a factor of four,
so there are some really lame manufacturers out there (the ones who
make the slower cards).
DirectX Compliance: 10.0
This is the level of support in hardware, for the latest Microsoft
graphics API. DX10 was introduced with Vista. The same hardware,
also has driver support for DX9c, so the card can be used in WinXP
as well. DX 9c is the minimum level of hardware support you should
buy today. If you're getting a card off Ebay, you could always go older
if you want, but for a new card, you can find a minimum of DX 9c
support pretty easily.
OpenGL Compliance: 2.1
OpenGL is an alternate way of rendering graphics. A typical use might
be in a CAD tool, or scientific visualization.
PS/VS Version: 4.0/4.0
These are "shaders", used for rendering. The higher this number, the
better these are at general purpose computing. Vista Aero minimum
version might be 2 or so.
Shader Processors: 40
Pipeline Layout: Super-scalar MADDx5
Texture Units: 4
Raster Operators 4
This is a measure of the parallel resources inside the GPU, for 3D
processing. There are two generations of terminology, and I don't
know how to translate the resources seen on older video cards, to
compare to the new way which is demonstrated by this video card.
Shader processors might go as high as 800, to give you some idea
how wimpy this card is.
Modern video cards also have a specialized feature for video playback,
which helps reduce CPU usage playing DVDs. The version of playback
accelerator is not listed on the example web page. Playback acceleration
currently only happens with a few applications - the acceleration
is not general purpose. This aspect of a card, is important to
people building HTPCs.
*******
Video card faceplates, have up to three output connectors. You can
use any two of three at a time. The DVI-I connector type, has two
sets of signals, digital and analog. With the following adapter,
it is possible to convert DVI-I to VGA.
http://www.htmart.com/files/images/DVI_pix/Adapter_DVI_I_f_to_VGA_m_lg.jpg
If the faceplate has a VGA connector, that only has one set of signals,
so cannot be converted to another format with a simple dongle.
Just make sure that the video card has something you can use to drive
your monitor. Exceptionally large monitors (Apple 30" Cinema) require
dual link DVI (uses all the digital pins), and more buyer research
is required to make sure the video card is good for the job. For
cheap LCD monitors, this is not usually a concern. This article on
DVI, discusses some of the many features of DVI.
(See "Example display modes")
http://en.wikipedia.org/wiki/Digital_Visual_Interface
HTH,
Paul
