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Can too much RAM cause problems?
- Thread starter d4z0mg
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About the same problems as being too rich and too good looking.
More RAM will eat battery faster, although how much faster is not completely clear. Early tests suggested that DDR4 draws significant amount of power even in idle, but the power consumption seems to be much better with the newer chips. At any rate, there is a probably couple of hours difference in battery life between the 64GB version and the 16GB.
If the RAM isn't in use it remains in a low-power state that probable won't much affect battery life. However, Apple OS loves to use up RAM when it can, which probably does take a bite out of battery life if there's more of it. Apple resisted offering more RAM for years because of power demands, they said. There's probably info about how much RAM is actually kept in use in one of the threads about how much RAM to get.
Define "in use". RAM is a volatile memory storage, it needs power to sustain its content. And it's not like RAM chips can be selectively disabled at random. If your system only uses 10GB of 32GB RAM it does not mean that the rest 22GB are turned off or something. It is true that RAM needs less power to sustain the data than to change it, but the question is how much less exactly... DDR4 is not necessarily optimized for idle power consumption, unlike LPDDR4 and friends.
That's exactly what it means.
LPDDR4 supports partial array refresh. Power gating turns off unused portions of the DRAM PHY. The power draw argument is an old wives tale that fools only the uninformed.
In use means storing data. The way it used to work is that RAM chips not in use were kept at a low-powered state, but since DDR4 doesn't have that the same way, I'd guess the OS just powers off RAM chips not in use. You can't power down part of a DDR4 chip as far as I know, but you can power down a whole one. There are a number of chips for 64GB.
But that's largely assumption, I haven't checked to see what they're doing with DDR4 to lessen its power use.
Downgrading RAM from 8GB to 4GB on a MacBookPro7,1 gained me extra 3 hours of battery life(battery is 10 years old btw) with the HDD. I would say unused RAM is a wasted RAM, so make sure you actually need it.
I am not an engineer so my understanding of this is very basic and most likely flawed. It seems that you know much more about it. If I understand the entire thing correctly, DDR4 will interleave reads and writes between multiple physical chips to increase bandwidth and hide latency. What this would mean is that allocation of physical (as in chip) RAM is not necessarily sequential. In this scenario, I am not sure how many chips are actually unused and how much power gating might help. Could you maybe shed some light on this?