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- Nov 24, 2001
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- Stillwater, Oklahoma
basically what the title says...i still have no idea the whole concept of dual ddr...please explain
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is dual ddr like raid 0?
- Thread starter RangerJoe
- Start date
- Joined
- Dec 17, 2000
simular...
as RAID 0 typically uses 2 hardives to acess each file, it (in theory) doubles the available bandwidth.
DCDDR will increase the avalible memory bandwidth to 128bitsx2 wide (from 64bitsx2 wide with DDR), so once again (like RAID 0) the theory says the RAM can work twice as fast.
But once again alot of the twice the speed is just theory
as RAID 0 typically uses 2 hardives to acess each file, it (in theory) doubles the available bandwidth.
DCDDR will increase the avalible memory bandwidth to 128bitsx2 wide (from 64bitsx2 wide with DDR), so once again (like RAID 0) the theory says the RAM can work twice as fast.
But once again alot of the twice the speed is just theory
Well, I don't think that dual channel DDR offers any more "speed." More bandwidth, yes. Speed, no. At least not in the sense when compared to RAID 0.
Let me explain. With RAID 0 you have two identical groups of data which are read simultaneously. In dual channel DDR there is still only one location for anyone one variable. You will be able to access more variables per unit of time but accessing one variable will still take as long.
I hope this was the type of answer you were looking for.
Let me explain. With RAID 0 you have two identical groups of data which are read simultaneously. In dual channel DDR there is still only one location for anyone one variable. You will be able to access more variables per unit of time but accessing one variable will still take as long.
I hope this was the type of answer you were looking for.
- Joined
- Jul 12, 2002
Not true. There is no duplication of data in RAID0. Each block (the smallest unit the file system can resolve) exists on one drive or the other, not both. If you compose a RAID0 array of two 20GB disks, you get a 40GB array. This cannot happen if data is duplicated. One block is written to one drive, the next to the other.
I agree the latency of the subsystem cannot be improved by this scheme. But the scheme itself is actually fairly analogous between the RAID0 disk array and a dual channel memory subsystem. While not a tremendous fan of analogies, I see no serious problem with this one.
I agree the latency of the subsystem cannot be improved by this scheme. But the scheme itself is actually fairly analogous between the RAID0 disk array and a dual channel memory subsystem. While not a tremendous fan of analogies, I see no serious problem with this one.
- Joined
- Mar 24, 2002
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- Liverpool, UK
I thought DDR was 64bit - so Dual DDR is 2x64bit???
its just that I always accepted that it was just the extra instruction on the fall that gives it its name and now any increases in the memory's bank size
- Joined
- Mar 24, 2002
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- Liverpool, UK
yes but that other guy said regular DDR is 64x2 and Dual-DDR is 128x2...
OP
- Joined
- Nov 24, 2001
- Location
- Stillwater, Oklahoma
- Thread Starter
- #10
hmm..
actually, i know what raid 0, 1, 0+1, and 5 are...but i didnt know what DCddr was...
in raid 0 (striping) a specific file is split evenly over the two drives and stored like that.
actually, i know what raid 0, 1, 0+1, and 5 are...but i didnt know what DCddr was...
in raid 0 (striping) a specific file is split evenly over the two drives and stored like that.
- Joined
- Mar 24, 2002
- Location
- Liverpool, UK
yes I know about the memory - its just the guy with all them lovely blue stars saying otherwise to what me brain says makes me doubt the old gray matter...
I think I partially explained this in another thread, but there are similarities and differences between DCDDR and RAID 0.
Conceptually, you can picture them accomplishing the same thing as both can double the throughput.
However, RAID writes data in serial stripes (i.e. it writes one stripe to the the first drive, then one to the second, then back to the first). DCDDR, on the other hand, reads and writes from both channels in parallel -- they are effectively bonded together. It is also important to note that RAID is really only efficient because of the cache on each drive. Without the buffering provided by that cache, RAID 0 would not give any performance benefit.
Conceptually, you can picture them accomplishing the same thing as both can double the throughput.
However, RAID writes data in serial stripes (i.e. it writes one stripe to the the first drive, then one to the second, then back to the first). DCDDR, on the other hand, reads and writes from both channels in parallel -- they are effectively bonded together. It is also important to note that RAID is really only efficient because of the cache on each drive. Without the buffering provided by that cache, RAID 0 would not give any performance benefit.
