2x16 or 4x8?

[Chrisism8]

Hi! First post in this awesome forum!

Background: I've started to plan for my upcoming Ryzen 5k build and I'm trying to settle on what Ram to use. My use case ain't super serious and I absolutely don't need every inch of performance I can get, but why not maximize the value if possible? Mostly use it for gamés, 3440x1440 so rarely CPU limited. Occasionally video edit/stream, but want to get more into that in the future. Parts are not locked in yet, but it is looking like a 170-200$ B550 board with either 5800x or 5900x. 

Question: I'm trying to decide on what RAM to get and I remember seeing this  Hardware Unboxed Video a while back on the topic of memory. I'm going for 32 GB, because it is decently cheap and I'm starting to get close to 12-14 GB today at times, so why not. I'm looking towards 3600 mhz, CL 18 sticks because that seem to be the price to performance sweet spot. 

Actual question: Should I go 2x16 or 4x8? Price wise, buying 2x16 cost as much as 2 packages of 2x8, and 4x8 one package is 15% more expensive. Looking at Corsair Vengeance CL18 3600 mhz where I live in Europe. What pros/cons are there to buying either versions?

Thanks you for the help!

[Helpful Tech Witch]

3 minutes ago, Chrisism8 said:

I'm looking towards 3600 mhz, CL 18 sticks because that seem to be the price to performance sweet spot. 

PCPartPicker Part List

Type	Item	Price
Memory	G.Skill Ripjaws V 32 GB (2 x 16 GB) DDR4-3600 CL16 Memory	$129.99 @ Newegg
	Prices include shipping, taxes, rebates, and discounts
	Total	$129.99
	Generated by PCPartPicker 2020-10-15 12:45 EDT-0400

cl16 3600 is ryzen sweet spot. Keep in mind this might change for r5000.

[porina]

Short version, there is no practical performance difference between them. The loading on the IMC will be the same assuming they're modern modules. If you go 2x16 you'll leave the door open to adding more ram in future should it be needed.

[svmlegacy]

5 minutes ago, Chrisism8 said:

Should I go 2x16 or 4x8? Price wise, buying 2x16 cost as much as 2 packages of 2x8, and 4x8 one package is 15% more expensive. Looking at Corsair Vengeance CL18 3600 mhz where I live in Europe. What pros/cons are there to buying either versions?

Depending on the modules, it will matter very little.

If the 8 GB DIMM's are single rank, and the 16 GB DIMM's dual rank, it's electrically very similar. Both will do what's on the box, as well.

2x 16 GB has the benefit of a cheaper upgrade path in the future.

[Haro]

Assuming both kits are identical in specs, they'll perform about the same, since ryzen cpu's only have 2 memory channels you wont get a bandwidth increase with 4 sticks (assuming both kits are identical) and with 2x16 gig, you'll have room for upgradability if needed later down the line. 

1 hour ago, Chrisism8 said:

I'm looking towards 3600 mhz, CL 18

a 3200 cl16/14 or a 3600 cl16 kit should do the job, though if that's not possible, a 3600 cl18 kit is about the same in terms of latency as a 3200 cl16 kit. 

1 hour ago, Chrisism8 said:

but it is looking like a 170-200$ B550 board with either 5800x or 5900x.

Currency or is it USD? if so..

Spoiler

PCPartPicker Part List

Type	Item	Price
Motherboard	Asus ROG STRIX B550-F GAMING ATX AM4 Motherboard	$189.49 @ B&H
	Prices include shipping, taxes, rebates, and discounts
	Total	$189.49
	Generated by PCPartPicker 2020-10-15 12:47 EDT-0400

PCPartPicker Part List

Type	Item	Price
Motherboard	MSI MAG B550 TOMAHAWK ATX AM4 Motherboard	$174.99 @ B&H
	Prices include shipping, taxes, rebates, and discounts
	Total	$174.99
	Generated by PCPartPicker 2020-10-15 12:47 EDT-0400

PCPartPicker Part List

Type	Item	Price
Motherboard	MSI B550-A PRO ATX AM4 Motherboard	$139.99 @ Amazon
	Prices include shipping, taxes, rebates, and discounts
	Total	$139.99
	Generated by PCPartPicker 2020-10-15 12:47 EDT-0400

PCPartPicker Part List

Type	Item	Price
Motherboard	Gigabyte B550 AORUS PRO ATX AM4 Motherboard	$169.99 @ Amazon
	Prices include shipping, taxes, rebates, and discounts
	Total	$169.99
	Generated by PCPartPicker 2020-10-15 12:47 EDT-0400

 

 To name some boards, and all of these are quite good. 

 

[JoostinOnline]

1 minute ago, porina said:

Short version, there is no practical performance difference between them. The loading on the IMC will be the same assuming they're modern modules. If you go 2x16 you'll leave the door open to adding more ram in future should it be needed.

That's not entirely true.  Some boards limit the maximum supported speed the more sticks you have.  Of course if he's only getting 3200MHz that won't be a problem, but if it was something faster it would really decrease the speed.

[Chrisism8]

1 minute ago, porina said:

Short version, there is no practical performance difference between them. The loading on the IMC will be the same assuming they're modern modules. If you go 2x16 you'll leave the door open to adding more ram in future should it be needed.

Yeah, in the video linked in the original post the difference is super small, but I thought "Hey, if they cost them same why not go for it :P" The likelihood of me ever needing 64 GB is close to 0 though. Thank you for your reply!

[Chrisism8]

2 minutes ago, svmlegacy said:

Depending on the modules, it will matter very little.

If the 8 GB DIMM's are single rank, and the 16 GB DIMM's dual rank, it's electrically very similar. Both will do what's on the box, as well.

2x 16 GB has the benefit of a cheaper upgrade path in the future.

Any easy way to see if they are single or dual rank? These are the modules I'm currently looking at. 
1. Corsair Vengeance LPX Black DDR4 3600MHz 2x16GB (CMK32GX4M2Z3600C18)
2. Corsair Vengeance LPX Black DDR4 3600MHz 2x8GB (CMK16GX4M2Z3600C18)

Note: Live in Sweden so not much use linking the websites, hope the partnumber makes sense. 

[porina]

4 minutes ago, svmlegacy said:

If the 8 GB DIMM's are single rank, and the 16 GB DIMM's dual rank, it's electrically very similar. Both will do what's on the box, as well.

8GB modules these days are single rank as far as I'm aware. Only in the early DDR4 days were some dual rank. I assume all 16GB modules are dual rank.

 

3 minutes ago, JoostinOnline said:

That's not entirely true.  Some boards limit the maximum supported speed the more sticks you have.  Of course if he's only getting 3200MHz that won't be a problem, but if it was something faster it would really decrease the speed.

It's not so much the number of modules as the rank loading. See above comment too. Loading would be practically the same as seen by IMC. 

[Chrisism8]

6 minutes ago, Haro said:

Assuming both kits are identical in specs, they'll perform about the same, since ryzen cpu's only have 2 memory channels you wont get a bandwidth increase with 4 sticks (assuming both kits are identical) and with 2x16 gig, you'll have room for upgradability if needed later down the line. 

a 3200 cl16/14 or a 3600 cl16 kit should do the job, though if that's not possible, a 3600 cl18 kit is about the same in terms of latency as a 3200 cl16 kit. 

Currency or is it USD? if so..

  Reveal hidden contents

PCPartPicker Part List

Type	Item	Price
Motherboard	Asus ROG STRIX B550-F GAMING ATX AM4 Motherboard	$189.49 @ B&H
	Prices include shipping, taxes, rebates, and discounts
	Total	$189.49
	Generated by PCPartPicker 2020-10-15 12:47 EDT-0400

PCPartPicker Part List

Type	Item	Price
Motherboard	MSI MAG B550 TOMAHAWK ATX AM4 Motherboard	$174.99 @ B&H
	Prices include shipping, taxes, rebates, and discounts
	Total	$174.99
	Generated by PCPartPicker 2020-10-15 12:47 EDT-0400

PCPartPicker Part List

Type	Item	Price
Motherboard	MSI B550-A PRO ATX AM4 Motherboard	$139.99 @ Amazon
	Prices include shipping, taxes, rebates, and discounts
	Total	$139.99
	Generated by PCPartPicker 2020-10-15 12:47 EDT-0400

PCPartPicker Part List

Type	Item	Price
Motherboard	Gigabyte B550 AORUS PRO ATX AM4 Motherboard	$169.99 @ Amazon
	Prices include shipping, taxes, rebates, and discounts
	Total	$169.99
	Generated by PCPartPicker 2020-10-15 12:47 EDT-0400

 

 To name some boards, and all of these are quite good. 

 

Is it worth going for CL16? Pricewise they are about 1450 (CL18) vs 1900 (CL16) Swedish Crowns. Roughly remove the last 0 to translate into USD. 

[Haro]

1 hour ago, Chrisism8 said:

Is it worth going for CL16? Pricewise they are about 1450 (CL18) vs 1900 (CL16) Swedish Crowns.

The switch from 3600 cl18 to 3600 cl16 wont be major for the most part, if it's a major price difference then you could just go for the 3600 cl18 kit. 

[svmlegacy]

6 minutes ago, Chrisism8 said:

Any easy way to see if they are single or dual rank? These are the modules I'm currently looking at. 
1. Corsair Vengeance LPX Black DDR4 3600MHz 2x16GB (CMK32GX4M2Z3600C18)
2. Corsair Vengeance LPX Black DDR4 3600MHz 2x8GB (CMK16GX4M2Z3600C18)

Note: Live in Sweden so not much use linking the websites, hope the partnumber makes sense. 

Corsair doesn't give specs regarding ranking. Like I said, it doesn't matter much, unless you're OC'ing.

4 minutes ago, porina said:

I assume all 16GB modules are dual rank.

16 GB single rank is getting more common by the day.

[Chrisism8]

Thanks for all the answers! Given me loads to think about... in like 15 mins. This forums is my new favorite !

[porina]

1 minute ago, svmlegacy said:

16 GB single rank is getting more common by the day.

That's new to me. Do you know when that started happening?

 

That does complicate matters for me. I'd rather go 4x8 in that case, because dual rank offers practical bandwidth improvements over otherwise identical single rank. But single rank could be easier to drive.

[svmlegacy]

1 hour ago, porina said:

That's new to me. Do you know when that started happening?

 

That does complicate matters for me. I'd rather go 4x8 in that case, because dual rank offers practical bandwidth improvements over otherwise identical single rank. But single rank could be easier to drive.

I might have been mistaken on that, but I could have swore I've read about single rank 16 GB dimm's I can't seem to find the source right now.

Regardless, the tech is there (32 GB DIMM's), and it is feasible.

 

I've never seen mulitple ranks increase performance though. Most of my experience in in DDR3, for that, additional ranks will drop performance slightly.
 

[porina]

13 minutes ago, svmlegacy said:

I've never seen mulitple ranks increase performance though. Most of my experience in in DDR3, for that, additional ranks will drop performance slightly.

Probably boils down to a "depends on workload" thing. On DDR4, synthetic tests like Aida64 show a small increase to bandwidth, trading off a small increase to latency. In a ram bandwidth limited compute use case, Prime95 with large FFT and similar, having dual rank (or equivalently 2 SR DPC) can give over 20% increase in performance with all other settings equal. Might be something to do with the way it mixes reads/writes. In limited gaming scenarios I've tried testing, I've not been able to show any significant difference beyond measurement variations.

 

I think I saw similar/same behaviour on DDR3 but it is long enough ago I can't be sure.

[rastafari310]

On 10/15/2020 at 8:21 PM, svmlegacy said:

I might have been mistaken on that, but I could have swore I've read about single rank 16 GB dimm's I can't seem to find the source right now.

Regardless, the tech is there (32 GB DIMM's), and it is feasible.

 

I've never seen mulitple ranks increase performance though. Most of my experience in in DDR3, for that, additional ranks will drop performance slightly.
 

 

you probably know, but this have apparantly changed for the ryzen 5000 series. 4 ranks(faster) vs 2 have shown to gain up to 8-10% in games according to gamers nexus. with cheap 16gb ram now..more often then not being single rank. id be careful not ending up with 32gb for example ..and only 2 ranks