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Comment by Xylakant | Hacker News Reader

I doubt that will happen ever, there's always a tradeoff between cost, speed and space (on the die, ...), otherwise we'd all be running machines with 1TB L1 Cache.

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Just because we've had to make tradeoffs so far does not mean these tradeoffs will always exist. Tradeoffs like these are not a natural law.

Yes they are, because the storage isn't arbitrarily small. There is always the latency of distance to overcome. That includes the centimeters to your main memory. There's always going to be a capacity-latency tradeoff.

That's a bit pedantic, though. The unavoidable tradeoffs are a pretty small part of the total that we're dealing with now.

L1 Cache is an order of magnitude faster than L2 cache and that's still all on the same chip. That's not "a pretty small part".

Energy consumption, heat dissipation, all of this becomes a larger problem for smaller structures. It's just easier and less error prone to build larger structures, yields are higher, so costs are lower for larger structures.

I'm certain the tradeoffs will change, but it's all limited by some physical law and while we can sometimes trade one law against the other, we can't currently break them, so tradeoffs will always exist.

I don’t disagree with you one bit, but I find it funny that you say: “we can't currently break them, so tradeoffs will always exist.” :)

(That “currently” is just a weasel word, but this being the Internet I understand why you put it there)

Well, I can rephrase that "I don't expect fundamental laws of nature to change any time soon." But laws that were assumed to be fundamental have been found to be false in the past, so I don't want to rule that out for the future either.

It is highly probable that we will discover memory that is better than current memory in every relevant metric (I suspect this is what you think you are claiming).

It is highly improbable that this new technology cannot be optimized in any relevant metric by trading off optimality in a different metric (this is what you are actually claiming).

The sentence “I'm certain the tradeoffs will change” implies that both your interpretations are wrong.

Yeah, but I thought we were talking about RAM vs SSDs. The problem there is not that SSDs are too big physically or that the cable is not short enough.

These caches are currently implemented with SRAM, a technology which uses 6 transistors per bit. Find a different technology (such as memristors) and our entire set of tradeoffs are likely to change.

The laws of physics dictate what the ultimate limits of a techology are; they do not dictate which technologies you actually choose to use.

> The laws of physics dictate what the ultimate limits of a techology are; they do not dictate which technologies you actually choose to use.

I never said so, I agree. I'm just stating that I'm confident that in the future, we'll still have tradeoffs. And I'm certain those will include "fast and small, but expensive" vs. "slow and cumbersome, but cheap".

We already reached the point where it's a problem that the clock signal on a die spreads so slow that it's a significant problem to increase the clock rate. So we're pushing parallel computing and other solutions, but those come with their own set of trades to make.

If nanoseconds were seconds

http://umumble.com/blogs/hardware/machine-perception-of-time...

Tradeoffs like these are not a natural law

They are, they're the laws of physics. According to known theories information cannot travel faster than the speed of light, so unless a very very radical new discovery is made sometime in the future, size and speed will basically be inversely proportional to each other.

The laws of physics don't dictate what technologies we know, only what their ultimate limits are. Just because our current memory technologies have some limitations that force us to make a tradeoff does not mean this will always be the case.

Just look back at how things were before the discovery of GMR[0]. We had very different tradeoffs then as compared to now.

[0] http://en.wikipedia.org/wiki/Giant_magnetoresistance

As long as we care about computational latency, the forces that give rise to caching will continue to hold force. The speed of light places a fundamental limit on the response time from a storage system of a given physical volume, and there are equivalent physical laws on the maximum amount of information that can be stored in that volume.

Which technologies we use for our caches and main storages will change, but we're never going to get around the need for caching.

Assuming you are still using a von Neumann architecture. You are arguing past chongli, not with.

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