Ram question

BigJohno

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Original poster
Jan 1, 2007
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I was listening to Macbreak weekley a few weeks ago and Rene Ritchie mentioned that the SSD and T2 chip is so fast now that you don't need to max out your ram anymore. What does he mean by thing? Do programs offload ram to storage and would there be a noticeable difference in performance between 16 and 32gb?

I have a 2013 Macbook pro for travel and remote work but it just chugs now with Photoshop. When i'm at home I have a pretty well spec'd pc with 32gb of ram. I'm wondering if 32 vs 16 would be a big issue in a new MBP.

My primary use case would be working with large photoshop files.
 

Audit13

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Apr 19, 2017
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When the MacBook runs out of available ram, it starts using virtual memory; i.e. it starts using swap space on the built in storage. Having data in ram can be accessed faster than data in the swap space. With faster bus speeds and SSD speeds, slow downs from reading data in the swap space can be reduced. This being said, more ram is better if you find the MacBook is running out of ram during normal use.
 
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deadworlds

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Jun 15, 2007
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I would question where this person got their information from. The fact of the matter is that RAM is and will always have faster read/write times than accessing any kind of hard drive be it SSD or traditional spinning platter. RAM sits closer to the CPU this allowing for a shorter travel path through the BUS from CPU to RAM. Accessing the SSD has to take a longer path this resulting in a slower read/write, even if you're using an SSD.

More Info:
https://hashnode.com/post/why-is-accessing-ram-always-faster-than-accessing-hard-drive-cijp7id47036t0f53sc3yq6dg
 

Audit13

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Apr 19, 2017
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That link is from 3 years ago and references a hard disk drive?

Distance isn't the only factor and may not matter as much in a logic board where the distance for each electrical trace is measured in mm.
 

deadworlds

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Jun 15, 2007
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That link is from 3 years ago and references a hard disk drive?

Distance isn't the only factor and may not matter as much in a logic board where the distance for each electrical trace is measured in mm.
It might be from three years ago but computer architecture design hasn’t changed much. The bus length are still farther from CPU to SSD vs CPU to RAM. I would reference a computer architecture book but I doubt anyone would bother reading it. Also RAM chips can make faster writes/reads than even an SSD. RAM can also make 16 concurrent reads or 16 concurrent writes making RAM much faster than SSD writes/reads.

More info: https://www.quora.com/How-is-RAM-faster-than-an-SSD
 
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Audit13

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Apr 19, 2017
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Toronto, Ontario, Canada
I'm not sure how one could measure the read/write difference between a 10 mm trace and 5 mm trace.

The link doesn't list any scientific data to support the assertion that distance plays a role in determining speed. The fact that a hard disk drive was mentioned indicates the use of cables and connectors which don't exist in a 2018 MacBook.

With a 2018 MacBook, will an end-user know the 16 GB MacBook is using virtual memory vs a 32 GB MacBook not using virtual memory? I don't know.

I do agree that reading and writing to ram is faster than reading and writing to an SSD.
 

deadworlds

macrumors 65816
Jun 15, 2007
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Citrus Heights,CA
You can check in activity monitor to see how much virtual memory youre currently using. I have on occasion actually maxed out my RAM and have had major file swapping occurring on my SSD. I did experience a slow down and a reduction in system response.

As to why accessing SSD is going to be slower its because the CPU has to first talk to the south bridge controller, this handles all peripheral traffic (HD, USB, etc). Then from the north bridge it accesses the SSD/HD. Then the information from the SDD/HD has to travel back to the northbridge and back to the CPU.

RAM on the other hand is directly connected to the CPU, this allowing almost instant read/writes to and from RAM.


Here’s is an article where they used a RAM disk and tested read/write speeds against an SSD on a MBA. It is 3 years old, but like I said, computer architecture hasn’t changed much so these should be pretty representative of how RAM will always be faster than any SSD or standard HD.
https://www.makeuseof.com/tag/ram-drives-faster-ssds-5-things-must-know/
 
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