Differences between DDR4 & DDR5 RAM - GoTechTalk


Friday, December 25, 2020

Differences between DDR4 & DDR5 RAM

So if there's more data in that row that needs to be read it's going to be way faster way more efficient and the maximum number of bits the ram can read from a row while it's open before needing to reopen it is called The Burst Length
By Sudarshan Yerunkar |  | Posted on 25th December 2020 | 🛍 Support me with your Amazon purchases: https://amzn.to/311Gk4H

Differences between DDR4 & GDDR5 RAM

If you've been thinking about building a new pc anytime soon, you'll have to make a decision should you wait and hold on for DDr5 or just go with DDr4 and because they are not backwards compatible. 

So to we will be going to try and give you all the information you'll possibly need about making a decision including what's the differences between ddr5 and ddr4 and when you can expect ddr5 to come out, so let's get into all the major differences between DDr4 and DDr5.

The first difference is memory bandwidth this is basically how fast data can be retrieved from or put onto the memory stick, it's kind of a big deal now with the maximum standard specifications ddr4 has a maximum bandwidth of up to 3.2 gigabits per second per pin and with ddr5 though the maximum spec has up to 6.4 gigabits per second per pin, although at first it'll probably be around 4.8 gigabits per second, so it's still a 50 increase and much better but eventually as RAM improves it'll get up to 6.4 double this bandwidth. 

Now I mentioned the bandwidth per pin ddr4 and ddr5 have the same number of data pins, so that's not going to make a difference here however the frequency of the memory is going to make a major difference that's the reason for the difference in memory bandwidth between the two, the standard ddr4 spec has a frequency range of between 1600 megahertz and 3200 megahertz whereas the ddr5 spec is double that between 3200 megahertz and 6400 megahertz but the eventual maximum number will probably be even higher than that, i mean even with ddr4 the maximum spec is just up to 3200 megahertz but you can see RAM up to about 5000 megahertz right now that's probably down to overclocking so technically 3.2 gigahertz is the max standard spec for ddr4 but of course it is higher so we'll probably see much higher than the 6.4 per pin on ddr5, in fact i've seen talk of about up to 8 400 megahertz for ddr5 but the main takeaway from all this is ddr5 will be capable of higher frequencies and therefore higher memory bandwidth overall. 

The next difference between ddr4 and ddr5 is Power Management Structure.

So, with ddr4 all the power management of the RAM slot is done on the motherboard itself whereas on ddr5 it's going to have an actual chip called a PMIC (Power Management Integrated Circuit) on the chip itself each individual chip will be able to manage its own individual power so theoretically this should mean that the ram is going to be more power efficient because (for example) if a individual ram dim module requires more power at a certain moment it will be able to get that power without having to increase the power to all the ram at once at least that is my understanding of it and also i'm not 100 sure how this will affect overclocking ram, you can do that right now through your bios on your motherboard not sure if you won't be able to do that or you will we'll have to see 

Next major difference between ddr4 and ddr5 is the Channel Architecture 

Now you may know that you can get like dual channel ram, quad channel ram with different slots in the motherboard this basically just makes it so the CPU can go out and access different pieces of data within each channel whereas if there's just one channel the CPU can basically only get one piece of data at a time it's kind of like having multiple cores in a CPU you can do multiple stuff at once as opposed to just one at a time. 

Now each ddr4 module has just one channel per stick and it's made up of 72 bits total that's 64 data bits and then eight bits for error correcting with ddr5 however each ram module or stick has two channels each of those channels is a 40-bit bus meaning it's going to have 32 bits of data pins and then eight for error correcting pins so effectively it's the same amount of data pins between ddr4 and ddr5 on each stick it's 64 for both however with ddr5 you're going to have two channels instead of just one, now like I said ddr4 already does support multiple channels however with ddr5 you can have two channels on each individual stick which means if there's two different pieces of data one in each channel that the CPU wants to access in different parts it can do both of those without having to wait for one or the other so each individual ram stick should be a lot more efficient and i assume this means we're going to be able to get a lot more potential channels in ddr5 

Now the next big difference between ddr5 and 4 is the so Burst Length. 

This one is going to be a little bit technical but i will try and explain it as best I can as simply as i can because it is pretty important, so ddr4 has a burst length of 8 whereas ddr5 has a burst length of 16. 

This did take a little bit of research on my part i'm not a super expert on this obviously i could be a little bit off in some parts but this is my understanding hopefully it should be helpful so if you were to zoom all the way into the stick of ram you would see that the data is stored in arrays which are just groups of rows and columns with each combination of the two having a bit when a certain piece of data in the form of a bit needs to be retrieved from the ram, the ram will first activate a row which basically prepares it to be read after a certain row is activated or opened then one bit from each row can be read from all the arrays simultaneously and then all of that data gets put into the output buffer to be sent to the CPU or whatever however this process of opening and activating a row is actually relatively slow so if you've ever looked at ram timings the TRCD is actually how long it takes to open a row you've seen that number before and if there's a different row already open it's going to take even longer because that row must be closed first and that amount of time is the TRP. 

So instead of doing this every single time you have to read one single bit what the ram can do is because that row is already activated for a short amount of time it can actually go ahead and read multiple columns within that row back-to-back so if there's more data in that row that needs to be read it's going to be way faster way more efficient and the maximum number of bits the ram can read from a row while it's open before needing to reopen it is called The Burst Length because it takes a burst of data at once instead of just getting each bit one at a time. 

So basically, while ddr5 is going to likely have very similar timings and latency numbers as ddr4 because it's going to have a longer burst length, in this case it means that in more situations it'll be able to read more data without having to have those delays happen as frequently meaning that overall it's just going to be able to access faster speed. 

All right now the final big difference between ddr4 and 5 is The Maximum Capacity. 

This is a pretty fun one because ddr5 has up to four times the maximum density of data as ddr4 specifically, ddr4 has up to 16 gigabits of data per die which is each individual little memory chip however ram manufacturers can actually put multiple of these dies on each side of the ram stick so this is called stacking, typically they can put about eight of these on each side and then they can do it on both sides this is called dual rank when you multiply all these together you get a grand total of 256 gigabits which is 32 gigabytes as the maximum amount of ram you're going to be able to fit on one stick of ram for ddr4 and that is probably consistent with what you'd see if you try to go out and buy a big stick of ram however with ddr5 you can have up to 64 gigabits of data per die so again when you multiply all that out 64 gigabits times 8 on each side times two sides and then you convert to gigabytes you get 128 gigabytes maximum per stick, however keep in mind it's going to take time for the manufacturing process to build up to that maximum density so at first when ddr4 first comes out you're probably going to still see a maximum individual stick at about 32 gigabytes and then it'll grow over time. 

So now that you know the differences between the two generations you might be wondering well when can I actually get this? 

Well hold on there before we jump into making that decision, right now you already do see ddr5 it exists but right now you can basically only see it in like high-end smartphones for example the Samsung galaxy s20 Samsung makes their own ram and so they can integrate it into their phones really easily, they're making the chips too now ram that's for actual computers and servers that's probably not going to be expected to roll out until around 2021 but just because ram manufacturers star making ddr5 ram doesn't mean you're going to actually necessarily be able to use it in your pc and that's because we need to wait for AMD and Intel to actually make CPUs and chipsets and motherboards that actually will support ddr5, with AMD some leaked internal memos reportedly suggest that they are planning to support ddr5 and usb 4.0 in 2022 and that's apparently when their next gen gen 4 micro architecture is released and that is kind of long ways off because as of writing this blog their gen 3 architecture just came out and with Intel some reported leaks show that it's likely that their 12th generation older late codename CPUs will support ddr5 but again this could take a while because even their 11th gen rocket lake CPUs are not even out yet so it's possible that the alder lake will be around the second half of 2021. 

So looking at all this it seems like the earliest you could possibly get a ddr5 computer is around the end of 2021 and that's only if alder lake from intel comes out by then but if they don't and it's a little bit later it'll probably come around the same time as AMD in 2022. 

So it's now decision time if you've been thinking about getting a new pc should you wait for ddr5 or not well there's a few things you need to consider first of all when ddr5 first comes out the difference between ddr4 and ddr5 is not going to be as big that's because ram manufacturers get better at producing better ram over time i mean ddr4 right now is way better than it used to be when it first came out yes ddr5 will still be significantly better than ddr4 but the price will be much more expensive at first with a smaller difference than down the line where ddr5 becomes more affordable and actually improves.

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