Hardware Reference
In-Depth Information
• Greater memory density, enabling fewer chips to be needed to reach a particular
memory size.
GDDR5 SGRAM
GDDR5SGRAMisbasedonthepreviousGDDRstandardswithseveralmodifications to
allow increased performance. The main differences include the following:
• Signal optimization using data/address bit inversion, adjustable driver strength, ad-
justable voltage, and adjustable termination
• Adaptive interface timing using data training that is scalable per bit or byte
•Errorcompensation, includingreal-time errordetection onbothread/writeandfastre-
sending
GDDR5 is also designed for extreme power management such that power is used only
when necessary. This allows higher clock speeds with cooler operation. Current GDDR5
parts are rated up to 7Gbps per chip, allowing 28GBps total bandwidth.
Video RAM Speed
VideoRAMspeedistypicallymeasuredinMHz,GHz,orbybandwidthinMb/GborMB/
GB per second. Faster memory and faster GPUs produce better gaming performance, but
at a higher cost. However, if you are primarily concerned about business or productivity
application performance, you can save money by using a video card with a slower GPU
and slower memory.
Unless you dig deeply into the technical details of a particular graphics card, determining
whattypeofmemoryaparticularcardusescanbedifficult.Becausenoneoftoday'svideo
cards feature user-upgradeable memory, I recommend that you look at the performance of
a given card and choose the card with the performance, features, and price that's right for
you.
RAM Calculations
The amount of memory a video adapter needs to display a particular resolution and color
depth is based on a mathematical equation. A location must be present in the adapter's
memoryarraytodisplayeverypixelonthescreen,andtheresolutiondeterminesthenum-
ber of total pixels. For example, a screen resolution of 1920×1080 requires a total of
2,073,600 pixels.
If you were to display that resolution with only two colors, you would need only 1 bit of
memoryspacetorepresenteachpixel.Ifthebithasavalueof0,thedotisblack,andifits
value is 1, the dot is white. If you use 32 bits of memory space to control each pixel, you
can display more than 4 billion colors because 4,294,967,296 combinations are possible
