SDRAM vs Rambus Analogy|
Confused about this whole SDRAM vs Rambus thing? Wish someone would explain the differences in plain English? Well, read on....
Think of SDRAM as a normal everyday car. Now, think of Rambus as an airplane. Assume that you need to get go visit your mom, who lives 120 miles away. Both of you also just happen to live right next to major airports. Well, the first time you're a bit low on cash, so you decide to just fill up your car, and drive down there. Since you can go an average of 60mph (mostly interstate), you get there in about 2 hours.
Well, next time you decide to visit (why can't she come up to visit anyways?), you've got some money so you're going to hop on a plane instead. It takes you 5 minutes to get to the airport, 10 minutes at the baggage check, another 30 minutes to board the plane, and another 15 minutes before take-off. For those of you not counting, that's 60 minutes so far. The airplane averages 600mph (it's flying with the wind as luck has it), so you get to your mom's airport in only 12 minutes, that's fast! It takes 5 minutes to get off the plane, 15 minutes to get your baggage, another 5 minutes to realize you had someone else's bag and get the right one, 10 minutes to the parking lot where your mom's waiting, and 5 more minutes to get to her house. So that's another 50 minutes once you got to her airport.
So, you add the 60 minutes it took to actually get in the air, the 12 minutes you were in the air, and the 50 minutes once you got out of the air. So it took 122 minutes, or 2 hours and 2 minutes. But wait a minute, you just spent $400 on plane tickets ($100 per person one-way, did I forget to mention you have a wife and two kids too?), versus the $15 in gas to fill-up your car, and it took LONGER? What's going on here? Since the plane's so much faster and costs so much more, why is it slower?
Well, it's not. Remember, it only took 12 minutes to actually get from one airport to another. It was the wait time, or the latency, that killed you. You see, you wouldn't want to take a 60 mile or even a 120 mile trip by plane, it's just a waste of time. Sure, the actual getting there is really fast, it's the waiting to get on your way that gets you. On the same note, if you needed to make a cross-country trip, you could hop on a plane and be there the same day, versus close to a week with a car.
What does all this have to do with SDRAM and Rambus, you say? Simple. RAMBUS is much, much, much, much, much (did I use enough much's?) faster than SDRAM. No, really, it is. Forget for now what everyone else (except for one person, not mentioning any names) has said. RAMBUS kicks SDRAM's butt in pure speed. SDRAM, slow, slow, slow. But, that's not all there is to the story. SDRAM, just like your car, is ready to go and send data to the CPU almost instantaneously. Rambus, like the airplane, takes a while to get going. So if your processor is requesting relatively small amounts of data, your SDRAM has already started up, sent the data (relatively slowly), and had time to sit down for a cup of coffee afterwards; while our good buddy Rambus is still charging its rocket engines ready to thrust the data at the cpu at ungodly speeds. Sure, it takes SDRAM 10 nanoseconds to transfer the data, and Rambus 1 nanosecond to do the same, but Rambus took 12 nanoseconds to get its "thrusters" ready.
So, what good is Rambus then? Plenty, actually. Any application that needs a good, steady stream of data should benefit. Higher Megahertz, er make that Gigahertz, processors will also see a benefit. But for normal applications with normal speed processors, SDRAM is king. In many cases its faster, and it's much, much cheaper. So for the price of Rambus, you can get somewhere between two and three times the amount of SDRAM in your system.
What about DDR RAM you say? Well, I'll leave that for another time :)
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