The title isn't need, it's should. Both are debatable of course, but I'd argue that should is a lot more defensible: Abstractions are leaky, and even if you can get by without knowing what's going on down there, you'll at the very least sharpen your mind and be more surefooted if you do.
What you're saying is a bit like the but I'll never need math in life argument. You're going to say that math is a lot more fundamental to existence then computer memory is of course, and that's true, but if you're looking at just computers, the way the memory system works is a fundamental part of the whole not entirely unlike math is to understanding nature. If you really want to know what you're dealing with and make sure you're not limiting yourself, you want to be inquisitive and go there.
Basically, I don't really get why the gut reaction to these sort of things (especially if they actually have meat; there's of course a lot of crummy pretenders) is so often to declare them pointless. Yes, you need to filter your information intake, but still, better err on the side of knowing too much.
No one is declaring this information pointless, but it's certainly a lot less relevant to Every Programmer than it was when this was written in 2007. I've actually got an okay understanding of this stuff, but the number of times that I've split
for(int i = 0; i < 10; i++)
{
j += i;
k += i;
l += i;
}
into
for(int i = 0; i < 10; i++)
j += i;
for(int i = 0; i < 10; i++)
k += i;
for(int i = 0; i < 10; i++)
l += i;
to reduce cache misses is very small because with today's hardware, it very often just doesn't matter. Obviously there are many programmers whose primary job is to do this, because they need every clock cycle they can squeeze out of the thing. They're just not representative of Every Programmer.
I'd argue it's more important now than when the white paper was first written. Where processor speed or memory size used to be the bottleneck, increasingly these days it's memory bandwidth instead, so managing that effectively is key to writing high performance programs.
I was going to say something almost precisely like this. The main thing I was going to add is that it is both memory bandwidth and latency that have become important bottlenecks, and often the latter is more important. You know how people were saying "disk is the new tape"? Guess what the new disk is? RAM. Much as with disk latencies, RAM latencies haven't really improved that much over the last decade or so, though memory bandwidth and CPU power have. Guess what that means? ;-)
..but you can only know this if you understand what's going on underneath the hood. So if you don't, no need to worry; you won't even know when the moment of your utter irrelevance arrives.
My typical response to the "I'll never need to know X" argument is similar, which is that having as broad and diverse understanding of a system as possible gives you imagination.
Without imagination, you will not be able to solve certain problems, not know where to even look when some arise, and at worse be totally unaware that better solutions exist.
That said, the OP's context is that of an "interview style" question which raises mental red flags for me. It's a common problem for interviewers to base their assessment of a candidate based on whether or not the interviewee has the same subset of knowledge that they do. In that case, I'd be quick to point out that:
What you're saying is a bit like the but I'll never need math in life argument. You're going to say that math is a lot more fundamental to existence then computer memory is of course, and that's true, but if you're looking at just computers, the way the memory system works is a fundamental part of the whole not entirely unlike math is to understanding nature. If you really want to know what you're dealing with and make sure you're not limiting yourself, you want to be inquisitive and go there.
Basically, I don't really get why the gut reaction to these sort of things (especially if they actually have meat; there's of course a lot of crummy pretenders) is so often to declare them pointless. Yes, you need to filter your information intake, but still, better err on the side of knowing too much.