How much faster is ddr2/ddr3 than Intel/OCZ SSDs?

[TidusZ]

As topic says, how much faster in numbers or in analogies is ddr2/ddr3 than Intel's and OCZ's high end ssds?

 

[alcoholbob]

Let's see
DDR-400 - 3,200MB/s
DDR2-800 - 6,400MB/s
DDR3-1600 - 12,000MB/s
Intel SSD - 250MB/s

 

[EarthwormJim]

Ram also can have latencies in the 50ns range, SSD's have access times in the .1 ms range ( 1x10^-4 vs 5x10^-8, rather HUGE difference).

 

[Cookie Monster]

Plus DDR2/3 are volatile while the memory technology used in the SSDs aren't (although some rare breed of SSDs are based on DRAM technology).

However like the others have already "suggested", a direct comparison between the two aren't very scientific since they are based on two different technologies that do two different things.

 

[magreen]

Well, since the OP asked for analogies and noone has provided one yet, here goes:

imagine you drive through the drive-thru at your favorite fast food place, like McDonalds. You order fries and a drink. You drive over to the pickup window and receive your fries and drink and pay for it. That took 2 minutes. Let's say that's like getting your data from RAM.

Now let's pretend that the pickup window was on the other side of the Atlantic Ocean from the order window, and all you have is a motorboat. You order your fries and drink at the order window, take your boat across the ocean and two weeks later you pickup your order! That's like getting your data from a nice new SSD. 😛

:laugh:

Of course, getting your data from a regular mechanical hard drive would be like plowing the field, planting the potatoes yourself, and waiting for them to grow so you can fry up those french fries 6 months later! :Q 😛

 

[ilkhan]

And with a spinning HDD, the pickup window is on Pluto. 😉

 

[magreen]

Originally posted by: ilkhan
And with a spinning HDD, the pickup window is on Pluto. 😉

see my edit 😉

 

[TidusZ]

Originally posted by: magreen
Well, since the OP asked for analogies and noone has provided one yet, here goes:

imagine you drive through the drive-thru at your favorite fast food place, like McDonalds. You order fries and a drink. You drive over to the pickup window and receive your fries and drink and pay for it. That took 2 minutes. Let's say that's like getting your data from RAM.

Now let's pretend that the pickup window was on the other side of the Atlantic Ocean from the order window, and all you have is a motorboat. You order your fries and drink at the order window, take your boat across the ocean and two weeks later you pickup your order! That's like getting your data from a nice new SSD. 😛

:laugh:

Of course, getting your data from a regular mechanical hard drive would be like plowing the field, planting the potatoes yourself, and waiting for them to grow so you can fry up those french fries 6 months later! :Q 😛

I rather enjoyed this. I also like those numbers for transfer rates, never realized ram moved stuff that fast to the processor. I want a ddr-2 120gb hdd.

 

[Idontcare]

Originally posted by: TidusZ
I rather enjoyed this. I also like those numbers for transfer rates, never realized ram moved stuff that fast to the processor. I want a ddr-2 120gb hdd.

And despite its speed, ram is slow as sh!t when it comes to moving stuff to the processor which is why we have L1, L2 and L3 caches coupled with aggressive pre-fetchers.

Consider 50ns latency for ram access versus the 1-2ns latency of on-die L2$.

(note 1ns = 1GHz, 0.5ns = 2GHz, 0.25ns = 4GHz)

For as pitiful slow as spindle-drives and SSD are, ram is pitifully slow as well. (but cheap, we get what we pay for)

 

[Denithor]

Depending on your situation, you can set up a RAMdisk to use a portion of system memory as a HDD. Certain applications (photoshop scratch disk) can really benefit from the much faster access times RAM offers over even a speedy SSD.

Just note - if your system crashes while you've got un-backed-up data on the RAMdisk - you'll lose whatever was in there.

Idontcare can give you a lot more detail on RAMdisks.

 

[magreen]

Originally posted by: Idontcare

Originally posted by: TidusZ
I rather enjoyed this. I also like those numbers for transfer rates, never realized ram moved stuff that fast to the processor. I want a ddr-2 120gb hdd.

And despite its speed, ram is slow as sh!t when it comes to moving stuff to the processor which is why we have L1, L2 and L3 caches coupled with aggressive pre-fetchers.

Consider 50ns latency for ram access versus the 1-2ns latency of on-die L2$.

(note 1ns = 1GHz, 0.5ns = 2GHz, 0.25ns = 4GHz)

For as pitiful slow as spindle-drives and SSD are, ram is pitifully slow as well. (but cheap, we get what we pay for)

Right. Now, to understand this, let's picture the L1 cache as fried chicken, the cpu as KFC and the pre-fetchers as The Colonel.

.
.
.

j/k :laugh:

 

[taltamir]

Originally posted by: TidusZ

Originally posted by: magreen
Well, since the OP asked for analogies and noone has provided one yet, here goes:

imagine you drive through the drive-thru at your favorite fast food place, like McDonalds. You order fries and a drink. You drive over to the pickup window and receive your fries and drink and pay for it. That took 2 minutes. Let's say that's like getting your data from RAM.

Now let's pretend that the pickup window was on the other side of the Atlantic Ocean from the order window, and all you have is a motorboat. You order your fries and drink at the order window, take your boat across the ocean and two weeks later you pickup your order! That's like getting your data from a nice new SSD. 😛

:laugh:

Of course, getting your data from a regular mechanical hard drive would be like plowing the field, planting the potatoes yourself, and waiting for them to grow so you can fry up those french fries 6 months later! :Q 😛

I rather enjoyed this. I also like those numbers for transfer rates, never realized ram moved stuff that fast to the processor. I want a ddr-2 120gb hdd.

and when you turn off your computer all your data goes "poof" and is gone.

I think a better analogy is a gun vs a car... Sure a bullet travels a lot faster then a car, but its not suitable as a mode of transportation.

Likewise RAM is like a bullet in speed compared to the car speed of a drive, but RAM is just not suitable for storage.