Weird memory question

[Trik'Stari]

Ok so I just watched the "as fast as possible" on DDR4 memory and I had a thought during Linus's builder analogy.

 

He equates memory to the tool belt and immediate vicinity of the builder, and equates the storage (hard drives and SSD's) to the truck or even I guess the toolbox in the truck.

 

Which leads me to the question, why are memory and storage seperate? why not use something like SSD's as ram?(so instead of having a toolbelt, you'd have a backpack full of tools) I'm not talking about in the current format of motherboards, this is simply hypothetical so assume an appropriate method of connection

 

I assume it's because DDR3 has faster read and write and what not, and that because memory needs to be temporary, and having it be partially permanent storage would be a problem.

 

Just thinking outside the box, wondering if anyone could answer this.

[dibthelegend]

A couple reasons, first off, SSD's are way slower than RAM. And RAM also has to be re-written constantly, hence the frequency they're clocked at. And since it has to be rewritten all of the time, it wouldn't work as a mass storage solution because it would be erased every time you turn off your PC. You can actually format what is called a "RAM disk" which basically partitions a portion of your RAM to act as mass storage in a RAID setup with another one of your drives, but those aren't terribly common and cause ridiculous start-up times (since it has to write the contents to the RAM disk every time you boot up).

[Trik'Stari]

So basically what I thought. Thanks for answering @dibthelegend

[Builder]

Ok so I just watched the "as fast as possible" on DDR4 memory and I had a thought during Linus's builder analogy.

 

He equates memory to the tool belt and immediate vicinity of the builder, and equates the storage (hard drives and SSD's) to the truck or even I guess the toolbox in the truck.

 

Which leads me to the question, why are memory and storage seperate? why not use something like SSD's as ram?(so instead of having a toolbelt, you'd have a backpack full of tools) I'm not talking about in the current format of motherboards, this is simply hypothetical so assume an appropriate method of connection

 

I assume it's because DDR3 has faster read and write and what not, and that because memory needs to be temporary, and having it be partially permanent storage would be a problem.

 

Just thinking outside the box, wondering if anyone could answer this.

They are separate because RAM is much more expensive than SSD flash is and so it can't be used in as high amounts.

 

Incidentally, SSDs are used like RAM, as are HDDs in most systems. It's called virtual memory, often implemented through a page file. https://en.wikipedia.org/wiki/Paging

[Trik'Stari]

They are separate because RAM is much more expensive than SSD flash is and so it can't be used in as high amounts.

 

Incidentally, SSDs are used like RAM, as are HDDs in most systems. It's called virtual memory, often implemented through a page file. https://en.wikipedia.org/wiki/Paging

Interesting.

 

My idea however was more along the lines of eliminating the separation between ram and storage, thus eliminating the need for a specialized memory standard, and cutting down on the cost of building a system.

 

The bigger question is, why do you need to have a "working" memory, could these operations not just be performed on the SSD itself?

 

The issue it seems is that even SSD's cannot match the speed of ram.

 

My idea basically is to combine ram with storage, so imagine that instead of ssd's and hdd's, (or ram) the entirety of the data (OS, programs etc) that your computer uses, is simply in one place (instead of 2 or more). Although it sounds like this causes the entire system to slow down and generally doesn't work.

 

still...interesting....now back to my beer and archer....

[Builder]

Interesting.

 

My idea however was more along the lines of eliminating the separation between ram and storage, thus eliminating the need for a specialized memory standard, and cutting down on the cost of building a system.

 

The bigger question is, why do you need to have a "working" memory, could these operations not just be performed on the SSD itself?

 

The issue it seems is that even SSD's cannot match the speed of ram.

 

My idea basically is to combine ram with storage, so imagine that instead of ssd's and hdd's, (or ram) the entirety of the data (OS, programs etc) that your computer uses, is simply in one place (instead of 2 or more). Although it sounds like this causes the entire system to slow down and generally doesn't work.

 

still...interesting....now back to my beer and archer....

It is all in one place. You can think of RAM and mass storage as lower levels of cache, in a manner of speaking. When you load a program, it gets read from the disk into the RAM, then on into L3 then L2 then L1 cache and finally it is processed and run.

 

Storage is like a funnel. As you go down into the funnel, the water pressure increases, but the volume also decreases. This is faster because reading everything directly from disk would actually take much longer than reading it into RAM and then L3 and so on. 

 

I think you'd be interested in this: The Infinite Space Between Words

 

The author is a terrible sexist, but he knows what he's talking about and takes the time to calculate tidbits like this one so I don't have to.

[Trik'Stari]

@Builder I get that it's in levels as you say, (I'll probably understand better after my 2 years in tech school), but why not simply increase the size of the L1 cache? (assuming that's the lowest level) I know that the cache memory is on the cpu chip itself, but if you assume the room for a (lets say 512 gig ssd) on the cpu itself, (ridiculous i know considering the price point of SSD's at the moment) could a CPU handle that?

 

oh wow, just clicked the link....SSD's are fucking SLOW compared to cache and ram......not to mention a system reboot.

 

 

I just realized how much of an eternity .68 seconds really is for a computer...... let alone a self aware android lol

[vm'N]

There is a bigger difference between cache and memory. There are multiple types of cache, and all are VERY important. The cache have it's associativity, it's specialty, it's organization method, it's addressing method, it's addressing type, it's assisting components, levels, identification schemes and much much more. Cache is REALLY big subject on CPUs.

The point of L1 cache is that it is so close the the processor core, the closer the better. If you increase it to much, you will end up with a bigger (that would end up further away) cache.

The bigger the cache-pool the slower it is. When the processor needs information it needs to read through ALL the L1 cache (or until it find what it needs), so it could potentially degrease its speed.

Also cache is on the CPU itself, so you are already there limited by size. RAM have a direct access to the north bridge (which have a direct access the CPU (NB is normally implemented on the CPU itself today)).

Something like a PCI SSD would need to access through the soughtbridge, which have to go through the northbridge. However, a SSD have some advantages. It can store much more, than an internal source like memory or cache, you can turn off your computer without losing your data, you are essentially not wasting up any system memory, and things who are not in use would not be used.

So you keep the internal sources small and fast, and keep the external big and slow. If the internal sources becomes to slow, it will hurt performance. If the external sources becomes to small, you lose capacity.

[Builder]

-snip-

Because as the storage gets faster, it gets more expensive. L1 cache is extremely expensive because it's on the CPU itself.

 

-snip-

I believe I mentioned it was a gross oversimplification, and I know and understand everything you said in your post.

[79wjd]

Look up mram. It's basically what you envisioned with ram and ssds being combined.