Does Memory Become Slower if Increased in Size?


Sometimes it is fun to speculate how differently your system would operate if changes were made to the hardware components. Today’s SuperUser Q&A post discusses increases in the size of memory to help satisfy a reader’s curiosity.

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

Photo courtesy of Association WDA (Flickr).

The Question

SuperUser reader spartacus wants to know if increasing the size of memory would cause it to become slower:

If we increased the size of SDRAM using the same technology, would the response time become slower? If it did become slower, would it be due to the complexity of digital logic?

Would an increase in size cause memory to become slower?

The Answer

SuperUser contributors Daniel R Hicks and Shikhar Bhardwaj have the answer for us. First up, Daniel R Hicks:

Yes and no. As duDE states, memory will never run faster than the bus/clock speed driving it, but the maximum speed of memory is definitely dependent on size.

As a memory assembly gets larger, the number of levels of address decoder increase (with the log of size), and the load on the drivers increases linearly (producing roughly a logarithmic increase in delay).

So, while it is rarely worthwhile to limit the size of RAM in a off-the-shelf system in an attempt to increase speed (there are exceptions where the box adjusts clock speed based on the size of RAM), if you are a system designer, the maximum RAM size is one of the performance trade-offs you must consider.

Followed by the answer from Shikhar Bhardwaj:

No, it does not. As SDRAM is synchronized with the system, memory speed depends on the speed of the system. What may affect the speed of memory access is the configuration it is used in.

If your build already has a dual-channel (or triple-channel) configuration, and the increased memory does not use identical modules, then you may slow down to single-channel operation. However, this decrease is hardly noticeable, as Wikipedia says:

  • Tom’s Hardware found little significant difference between single-channel and dual-channel configurations in synthetic and gaming benchmarks (using a “modern (2007)” system setup). In its tests, dual-channel gave at best a 5 percent speed increase in memory-intensive tasks.

In this case, the speed may decrease, but you will experience an overall boost in performance due to the greater amount of physical memory available to your operating system. This, of course, depends on the operating system you are using and how efficient it is at utilizing the available resources.

Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

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