| |
|
Corsair TwinX1024-3200LLPro
(Impact of Technology) |
Page read
2846
times |
| |
|
|
|
| |
|
What is Dual Channel |
|
There is no such thing as Dual channel memory, you only have dual
channel platforms. Dual channel is your computers ability to use 2
memory pathways. Theoretically this should double your bandwidth but
that's not always the case. Not all motherboards support Dual channel
DDR, in fact there are very few platforms that provide this support.
The first company to support Dual Channel DDR was NVIDIA with there
N-Force 2 chipset for the AMD processor and then Intel followed with
the Springdale (i865PE) and Canterwood (i875P) chipsets. Dual Channel
is not a new idea the past solutions though where too proprietary and
way to high cost. The i850, i850E, and i860 chipsets from Intel
supported Dual Channel memory using RIMM but that proved to cost way
to much and didn't give great performance gains. |
|
|
|
|
Memory latency |
With memory speeds getting faster most manufacturers are relaxing the
memory's timings just to keep up. The thing you have to remember is
just because you have two different brand PC-3200 sticks does not mean
they are both the same speed. Memory timings are a huge part of system
performance that is overlooked most of the time. Your memory's latency
is normally called CAS (Column Address Strobe)
the CAS will range from CAS2, CAS2.5, and CAS3 on DDR modules.
|
|
|
DDR (Double Data Rate) memory can transfer data
on the rise and fall of the clock signal. This means it can transfer
data at double the speed of the memory buss. Your memory's latency is
measured in clock cycles so if you are using CAS3 memory your system
has to wait 3 clock cycles before it can transfer data to the memory,
that's 6 wasted transfers. On the other hand if you are using CAS2
memory you are only wasting 4 data transfers instead of 6. This may
not seem important but with the amount of clock cycles your computer
makes in a second it's a huge difference in system performance. |
|
|
Imagine this, your system buss running at 200Mhz which is what the
newest AMD and Intel processors are running at. At 200MHz your buss
will generate 200 million clock cycles a second. Can you see now why
latency is so important? Lets just say your system transfers one
bit of data at a time and has to wait on the latency before
transferring each one. If you are using CAS3 memory your system will
be wasting 133 million clock cycles each second that's 266 million
wasted transfers in or out of memory a second. Now on
the other hand if you are using CAS2 memory you will only be wasting
100 million clock cycles a second or 200 million transfers in or out
of memory a
second. It still looks like a huge number but you are saving 33
million clock cycles a second and providing your system with 66
million transfers in or out of memory a second. That's a 25% improvement, now
real life results are not like this because your system doesn't
transfer one bit at a time in fact DDR transfers 8 bits at a time in
two sets of 4. |
|
|
Now with that in mind its time to get more complicated. CAS is not
the only timing your memory has. There are 3 more important timings that we will go over
now. There's RAS to CAS Delay, RAS Precharge, and Cycle time or tRAS. Lets go
over these briefly. |
|
|
- RAS to CAS Delay
- The RAS to CAS Delay is the amount of
time that the memory stays open after the CAS delay. It is important
to leave this large enough to be able to get all the data sent.
Since DDR transfers 8 bits a clock cycle in the form of 2 sets of 4
bits this should not fall below 2 or it will not allow all the data
to stay in memory before the next transfer begins.
- RAS Precharge
- This is the interval of time
between finishing the previous access and beginning the next access.
A minimum dead time is required between the consecutive accesses.
This is the precharge time. I guess you would consider this giving
the ram a short smoke break.
- Cycle time (tRAS) - This is the maximum amount of time a bank is left open from the activate command to the precharge
command. This setting should not be to high or you run the risk of
your memory just sitting there when it could be working. On the
other hand if this is set to low your memory may not have enough
time to do all the read and write requests it needs to.
|
|
|
|
Next
More about Corsairs 3200LLPro >>> |
|
|
|
|
|
|
|
|
Talk
about this review in the Forum |
|
|
|
|
| |
| |
