Jump to content
Search In
  • More options...
Find results that contain...
Find results in...

PCIE 4.0 system usage of PCIe 3 card

There should be none to zero differences because GPUs dont even use all the bandwidths from PCIe 3.0 (16x).

Even using PCIe 8x makes no difference at all.

The nice thing about this is, that there should be more PCIe-m2 slots, because 2x PCIe 4.0 is as fast as PCIe 3.0 4x.

 

The above is from reddit post 

 

I wanna ask if you have CPU with PCIe 4.0 and also motherboard that supports it but GPU that is one gen down - PCIe 3.0

Does that mean that the card automatically receives only max 8x PCIe lanes and uses only 4x lanes, unlike on 3.0PCIe system where it uses "16x lanes" but in the real world only 8x lanes? 
 

PCIE 4.0 doubles the "bandwidth" that's why i said 8x lanes and 4x lanes which in 3.0 terms are equal to 16x and 8x lanes or 16GB and 8GB and (4.0 PCIe 8x lanes = 16GB and 4x lanes 8GB)

so to my initial question, would the card then really only need 8/4x lanes on pcie 4.0 system while card remains 3.0pcie? 

 

"using PCIe 4.0 card on PCIe 4.0 system remains the same as PCIe 3.0 -at least the way it operates. Card would still require 16x lanes and used only 8x lanes, but the difference here would be only in double bandwidth bcuz whole pcie has been designed that way,

 

so pcie4 card with 4.0 system (mobo, cpu) would work the same way as having whole system with pcie3 (pcie3.0 mobo, cpu, gpu) speaking hypothetically that is. but it would work differently if you put 3.0 card in 4.0 system"

 

meaning 3.0 card wouldnt eat 16 lanes on 4.0 system but rather only 8 lanes (8lanes meaning (8*2GB=16GB) instead of 8*1GB which would be on pcie 3.0 and actaully it would be 16*1GB)

 

 

IK IT IS CONFUSING I'm sorry in ADVANCE

 

 

 

 

 

 

 

Link to post
Share on other sites

The pci-e 4.0 bus gets downgraded to pci-e 3.0 when you insert a video card that can only use pci-e 3.0

 

pci-e 2.0 means 500 MB/s per lane, pci-e 3.0 means approx. 970 MB/s per lane, pci-e 4.0 means approx. 1940 MB/s per lane.  

 

So when you insert a pci-e 3.0 video card into a pci-e 4.0 slot, it will simply run at pci-e 3.0 x16, with a maximum available bandwidth of 16 x 970 MB/s or around 15.5 GB/s

 

The number of pci-e lanes doesn't change. 

 

In a lot of games the difference between pci-e 3.0 x8 (~7.5 GB/s) and pci-e 3.0 x16 ( ~15.5 GB/s) is let's say less than 3% fps ... something like 100fps vs 97 fps. 

With pci-e 4.0 video cards, it should be even less noticeable, as pci-e 4.0 x8 is same bandwidth as pci-e 3.0 x16. 

 

Link to post
Share on other sites

If you have 16x 4.0 available lanes and 3.0 cards and you put 2 cards into the PC, they will both run at x8 3.0 speed so there is no benefit from the slots being 4.0.

 

If the cards are 4.0 they will run at x8 4.0 speed so there is benefit from the 4.0 link as each card is effectively at x16 3.0 bandwidth. 

Link to post
Share on other sites

you're getting confused.

 

a PCIe3.0 16x card in a PCIe4.0 16x slot will run at PCIe3.0 16x

 

the x configuration doesn't change unless it's down to chipset or manual control for lane sharing, generation doesn't affect that

 

the effective "x" amount changes because the bandwidth per generation roughly doubles, but the actual number of lanes used does not change between generations. the number of lanes used only changes if it's manually specified or if the lanes are being split out to be shared between devices

get money, acquire catgirls, fold proteins

 

systems:

Spoiler

Main - Zenith.
R9 3900x 4.25GHz All-Core // X570 Aorus Ultra // 32GB Predator 3200MHz // 3090 FTW3 Ultra // Meshify S2 White/Black (Foam Filter Delete)

(Upgrade in consideration: R9 5900x)

 

Folding Station - Polaris.

i7-4790k 4.8GHz // Z97X-UD5H // 32GB Dominator Platinum 2133MHz // 2080Ti Lightning Z // Define R6 (Front Panel Mod/Delete)

 

TV / LAN / VR machine - The Hiss.

R5 3600 4.25GHz All-Core // B450i Aorus Pro Wifi // 16GB Predator RGB 3200MHz // Vega64 Silver (Air) // Phanteks Evolv ITX (Front Panel Mod)

(Upgrade in consideration: R9 3900x 4.25GHz All-Core // B550i/X570i Aorus Pro Wifi // RTX 3080 XC3 Hybrid or 3080 Aero)

 

Laptop / Mobile Workstation

i7-8750H // Asus FX705GM // 32GB 2400MHz // 1060 6GB

 

Link to post
Share on other sites
Just now, WereCat said:

If you have 16x 4.0 available lanes and 3.0 cards and you put 2 cards into the PC, they will both run at x8 3.0 speed so there is no benefit from the slots being 4.0.

 

If the cards are 4.0 they will run at x8 4.0 speed so there is benefit from the 4.0 link as each card is effectively at x16 3.0 bandwidth. 

aha okay, but in theory, the cards would only consume 4x lanes or 8GB or in terms of 3.0 speaking 8lanes each 

bcuz more than 8GB of bandwidth almost non of 3.0 card uses 

just like 3.0.. you have dedicated 16lanes but in reality it only uses 8lanes bcuz it doesnt need more than that 99% of the time

am i correct?

Link to post
Share on other sites
Just now, Klemen said:

aha okay, but in theory, the cards would only consume 4x lanes or 8GB or in terms of 3.0 speaking 8lanes each 

bcuz more than 8GB of bandwidth almost non of 3.0 card uses 

just like 3.0.. you have dedicated 16lanes but in reality it only uses 8lanes bcuz it doesnt need more than that 99% of the time

am i correct?

No, the lane number doesn't change, the speed of each does.

Link to post
Share on other sites
2 minutes ago, yaboistar said:

you're getting confused.

 

a PCIe3.0 16x card in a PCIe4.0 16x slot will run at PCIe3.0 16x

 

the x configuration doesn't change unless it's down to chipset or manual control for lane sharing, generation doesn't affect that

so if i put 4.0 NVMe then that nvme would run on 4.0 while gpu would run on 3.0?

Link to post
Share on other sites
13 minutes ago, Klemen said:

Even using PCIe 8x makes no difference at all.

That's just wrong. There's plenty of games that will completely saturate PCIe 3.0 at 8x. It is true however, that there's not much point to PCIe 4.0 one way or another right now. Even the new 30-series cards, while PCIe 4.0, do not use more than PCIe 3.0 16x can provide.

CPU: AMD Ryzen 9 5900X · Cooler: Artic Liquid Freezer II 280 · Motherboard: MSI MEG X570 Unify · RAM: G.skill Ripjaws V 2x16GB 3600MHz CL16 (2Rx8) · Graphics Card: ASUS GeForce RTX 3060 Ti TUF Gaming · Boot Drive: 500GB WD Black SN750 M.2 NVMe SSD · Game Drive: 2TB Crucial MX500 SATA SSD · PSU: Corsair White RM850x 850W 80+ Gold · Case: Corsair 4000D Airflow · Monitor: MSI Optix MAG342CQR 34” UWQHD 3440x1440 144Hz · Keyboard: Corsair K100 RGB Optical-Mechanical Gaming Keyboard (OPX Switch) · Mouse: Corsair Ironclaw RGB Wireless Gaming Mouse

Link to post
Share on other sites
Just now, KaitouX said:

No, the lane number doesn't change, the speed of each does.

aha okay so only speed is affected while lanes  remain the same, basically almost nothing dramatically changes at all, right?

Link to post
Share on other sites
Just now, Klemen said:

so if i put 4.0 NVMe then that nvme would run on 4.0 while gpu would run on 3.0?

providing the slot you're putting that 4.0 device into is a 4.0 slot, yes, that's correct

get money, acquire catgirls, fold proteins

 

systems:

Spoiler

Main - Zenith.
R9 3900x 4.25GHz All-Core // X570 Aorus Ultra // 32GB Predator 3200MHz // 3090 FTW3 Ultra // Meshify S2 White/Black (Foam Filter Delete)

(Upgrade in consideration: R9 5900x)

 

Folding Station - Polaris.

i7-4790k 4.8GHz // Z97X-UD5H // 32GB Dominator Platinum 2133MHz // 2080Ti Lightning Z // Define R6 (Front Panel Mod/Delete)

 

TV / LAN / VR machine - The Hiss.

R5 3600 4.25GHz All-Core // B450i Aorus Pro Wifi // 16GB Predator RGB 3200MHz // Vega64 Silver (Air) // Phanteks Evolv ITX (Front Panel Mod)

(Upgrade in consideration: R9 3900x 4.25GHz All-Core // B550i/X570i Aorus Pro Wifi // RTX 3080 XC3 Hybrid or 3080 Aero)

 

Laptop / Mobile Workstation

i7-8750H // Asus FX705GM // 32GB 2400MHz // 1060 6GB

 

Link to post
Share on other sites

you split by lanes, and then the lanes will run at the lowest pcie gen between two devices

 

you cant split by bandwidth unfortunately

My PCs: Desky | Beddie | Miney | Benchie

Things I need help with: (nothing at the moment)

Spoiler

none atm

I hate Intel's pricing, Ryzen's weird quirks, Nvidia's pricing, and Radeon GPUs in general

Spoiler

Products I like:

Spoiler

Sony Xperia Z1 / Z2 / 10 ii, Asus Strix 970 / 1070, Samsung SSD, WD HDD, Corsair PSUs (AX, RM, CX(grey)), GeForce GPU, NZXT N450/S340, be quiet! Coolers, G.Skill Trident RAM, Logitech M525, Logitech G440, Razer Deathadder Elite

Products I hate:

Spoiler

Xperia Z3, XiaoMi 5c, Radeon GPUs, Razer Audio Products, any bloatwares

Companies I absolutely adore: (and hope it stays that way)

Spoiler

be quiet! - sent me AM4 mounting for my DRP3 even though it's way past the timeframe stated, no questions asked

Corsair - very good RMA experience, absolutely recommend

Companies I hate:

Spoiler

Nvidia, Intel, Apple, TMT (Thundermatch, a retailer)

Personal Blacklisted Companies:

Spoiler

Acer: shit tier quality products, shit tier customer service thus far, they "tried" to solve my issue but they arent really doing anything but delaying and delaying. (on-going case since July)

Gigabyte: horrible customer service (gigabyte had literally 0 customer service, asked me to go to retailer with NO WAY to email them about a question) but at least they fixed my shit in ONE MONTH (would probably take me 1 hour to fix if they let me email them)

XiaoMi Phones: built like a tank but the software is buggy as all hell

Seagate HDD: had too many dead seagate drives

Kingston SSD: 300V controller swap thingy

Razer (except their mouse)

Remember, just because I had good/bad experiences with these companies/product, doesn't mean you will have similar experiences too. I would still recommend these products if they made sense for your needs, but I'll add a disclaimer of my experience if it's relevant. Feel free to DM me asking why they are where they are.

 

Link to post
Share on other sites
Just now, Chris Pratt said:

 Even the new 30-series cards, while PCIe 4.0, do not use more than PCIe 3.0 16x can provide.

meaning that equals to 8x on PCIe 4.0?

and the def of that sentence doesnt changes and still applies here

Link to post
Share on other sites
Just now, yaboistar said:

providing the slot you're putting that 4.0 device into is a 4.0 slot, yes, that's correct

aha okay thx 

Link to post
Share on other sites
Just now, Klemen said:

so if i put 4.0 NVMe then that nvme would run on 4.0 while gpu would run on 3.0?

The answer is it depends on how the pci-e lanes are routed between the cpu and slots and m.2 connectors. on some motherboards, the m2. connector may be downgraded to pci-e 3.0 speeds as well, but most of the cases it should stay at pci-e 4.0

 

Either way, a M.2 x4 pci-e 3.0 SSD  typically reaches up to 3.5 GB of transfer speed, and most m.2 pci-e 4.0 SSDs go up to 5.5 GB/s  - do you really think you'd notice the difference between 3.5 GB/s and 5.5 GB/s ?

A typical game will load a few hundred MB of data from drive when you load a game level, and that takes seconds to read from ssd... a pci-e 4.0 ssd won't make your games faster compared to a pci-e 3.0 ssd, most of the time is used processing the data that was read and converting it to the formats your video card understands and supports, and that's done in cpu and ram. 

 

Link to post
Share on other sites
1 minute ago, Moonzy said:

you cant split by bandwidth unfortunately

yea, i didnt mean that

 

i meant if the cards would run similarly like you know if you have 1 card and compering it to two system one with 3.0 and another one with 4.0

3.0 would use 16x lanes

while 4.0 could only use 8x lanes, but the bandwidth would remain the same 

 

- speaking that "that gpu is both 4.0 and 3.0 at the same time, HYPOTHETICALLY speaking"

Link to post
Share on other sites
Just now, Klemen said:

3.0 would use 16x lanes

while 4.0 could only use 8x lanes, but the bandwidth would remain the same

yes, then you would see no performance difference, since bandwidth is theoretically the same

 

and yes, if a GPU is capable of 4.0, it is also capable of 3.0, also 2.0, and 1.1

My PCs: Desky | Beddie | Miney | Benchie

Things I need help with: (nothing at the moment)

Spoiler

none atm

I hate Intel's pricing, Ryzen's weird quirks, Nvidia's pricing, and Radeon GPUs in general

Spoiler

Products I like:

Spoiler

Sony Xperia Z1 / Z2 / 10 ii, Asus Strix 970 / 1070, Samsung SSD, WD HDD, Corsair PSUs (AX, RM, CX(grey)), GeForce GPU, NZXT N450/S340, be quiet! Coolers, G.Skill Trident RAM, Logitech M525, Logitech G440, Razer Deathadder Elite

Products I hate:

Spoiler

Xperia Z3, XiaoMi 5c, Radeon GPUs, Razer Audio Products, any bloatwares

Companies I absolutely adore: (and hope it stays that way)

Spoiler

be quiet! - sent me AM4 mounting for my DRP3 even though it's way past the timeframe stated, no questions asked

Corsair - very good RMA experience, absolutely recommend

Companies I hate:

Spoiler

Nvidia, Intel, Apple, TMT (Thundermatch, a retailer)

Personal Blacklisted Companies:

Spoiler

Acer: shit tier quality products, shit tier customer service thus far, they "tried" to solve my issue but they arent really doing anything but delaying and delaying. (on-going case since July)

Gigabyte: horrible customer service (gigabyte had literally 0 customer service, asked me to go to retailer with NO WAY to email them about a question) but at least they fixed my shit in ONE MONTH (would probably take me 1 hour to fix if they let me email them)

XiaoMi Phones: built like a tank but the software is buggy as all hell

Seagate HDD: had too many dead seagate drives

Kingston SSD: 300V controller swap thingy

Razer (except their mouse)

Remember, just because I had good/bad experiences with these companies/product, doesn't mean you will have similar experiences too. I would still recommend these products if they made sense for your needs, but I'll add a disclaimer of my experience if it's relevant. Feel free to DM me asking why they are where they are.

 

Link to post
Share on other sites
26 minutes ago, Klemen said:

There should be none to zero differences because GPUs dont even use all the bandwidths from PCIe 3.0 (16x).

WE KNOW ...wtf

| CPU: Core i7-8700K @ 4.89ghz - 1.21v  Motherboard: Asus ROG STRIX Z370-E GAMING  CPU Cooler: Corsair H100i V2 |
| GPU: MSI GTX 1080Ti Gaming X Trio 2ghz OC  RAM: 32GB T-Force Delta RGB 3066mhz |
| Displays: Acer Predator XB270HU 1440p Gsync 144hz IPS Gaming monitor | Oculus Rift S

Link to post
Share on other sites
20 minutes ago, mariushm said:

The answer is it depends on how the pci-e lanes are routed between the cpu and slots and m.2 connectors. on some motherboards, the m2. connector may be downgraded to pci-e 3.0 speeds as well, but most of the cases it should stay at pci-e 4.0

 

 

 

well i mean like, NVMe take lanes from  chipset to put that in prospective, i think comparing B550 and X570 motherboard's chipsets,

chipset on B550 uses 3.0 lanes while, X570 chipset uses 4.0 pcie lanes

if that's what you meant by "it depends" 

Link to post
Share on other sites
36 minutes ago, mariushm said:

 

 

In a lot of games the difference between pci-e 3.0 x8 (~7.5 GB/s) and pci-e 3.0 x16 ( ~15.5 GB/s) is let's say less than 3% fps ... something like 100fps vs 97 fps. 

With pci-e 4.0 video cards, it should be even less noticeable, as pci-e 4.0 x8 is same bandwidth as pci-e 3.0 x16. 

 

Yea, i agree. but that means cards that are 4.0 and are in the system that supports 4.0 will be automatically put to 8x lanes

like 3.0 cards are set to 16x lanes? 

 

You know, i have 3.0 card and if i check bios or aka uefi, it says it's using "16x lanes"

does then using 4.0 card displays 8x lanes? (speaking 4.0 8x is the same as 3.0 16x ofc) 

Link to post
Share on other sites

Unless you are doing 320Hz Gaming you have no need for PCI-e 4.0 on graphics.

If you are doing 8k, 4k or 1440p gaming you are unlikely to have enough GPU power to actually hit that level of FPS to trigger a bottleneck.

Remember it isn't 8k or 4k that is filling the pipeline its the calls for the FPS, the resolution is not a big issue.

 

a 3070,3080 or 3090 at 1080p gaming with a 320Hz screen may be able to bottleneck a 3.0 Slot and require a 4.0 pcie slot.

from memory 190fps was around the limit on the 2080ti where performance started to drop but there was enough GPU power to push it faster.

 

Maybe the 30 series will show us the limit, but realistically you need specific monitor and lower res to see his problem, most players are not in the 200+ area of FPS to see this problem yet...

 

if you are pumping out 100FPS and have something like a gsync 100Hz monitor pushing two m.2 drives at 3Gbps you'd likely have enough room to do that without any issues.

Even if you were gaming like that what game is going to be pulling down 6Gbps for more than a few seconds to load, its not going to be pulling down 6Gbps non stop not even Cyberpunk is going to be that big. you'd have to have a game that is 200GB or something that is drawing m.2 drive calls constantly, that type of action is going to be game developed with a loading screen more than likely.

 

This is likely an issue we'd see with old hardware in 2-3 years time with a modern title :)

 

CPU | Intel i7-8086K Overclocked 5.4Ghz @ 1.44v | GPU | EVGA 1080 FTW2 Overclocked 2190Mhz | PSU | Corsair RM850i | RAM | 4x8GB Corsair Vengeance 3200MHz |MOTHERBOARD | Asus ROG Maximus X Formula | STORAGE | 2x Samsung EvO 256GB NVME  | COOLING | Hard Line Custom Loop D5 Pump Monsta 480mm Radiator  | MONITOR | Acer Predator X34 | OS | Windows 10

Link to post
Share on other sites
8 hours ago, Klemen said:

well i mean like, NVMe take lanes from  chipset to put that in prospective, i think comparing B550 and X570 motherboard's chipsets,

chipset on B550 uses 3.0 lanes while, X570 chipset uses 4.0 pcie lanes

if that's what you meant by "it depends" 

nvme doesn't take lanes ... it's just a specification, like a standard that defines how to connect and interact with storage that connects directly to cpu

 

Otherwise... no.

 

The processor has a built in pci-e controller, which creates 24 pci-e lanes. These 24 lanes are arranged like this:

* 16 pci-e lans go to video card slot, or the first two pci-e x16 (x8 electrically)

* 4 pci-e lanes go to the first m.2 conector

* 4 pci-e lanes are used to connect the chipset to cpu.

So actually 20 pci-e lanes  are acessible by users.

 

The chipset takes the 4 pci-e lanes and inside the chip there's a pci-e controller which creates more pci-e lanes : 8 pci-e 3.0 lanes for the B550 models, 8 pci-e 4.0 lanes for the x570 model. 

 

On both B550 and x570 the pci-e lanes going to pci-e x16 slot and m.2 connector are pci-e 4.0 , just the 4 lanes going to chipset are limited to pci-e 3.0.

 

However, I know at least one motherboard that contains that has 3 m.2 connector, all capable of pci-e 4.0

They do this by splitting the pci-e x16 from the video card into a pci-e x8 and 2  pci-e x4. So because they do this, if you insert a pci-e 3.0 in the two m.2 connectors that are involved, the pci-e x8 going to video card will he downgraded to pci-e 3.0 as well

 

 

Link to post
Share on other sites

Hardware Unboxed did some testing on this today and i will attach the images from their youtube video.

 

4.02.PNG

4.01.PNG

CPU | Intel i7-8086K Overclocked 5.4Ghz @ 1.44v | GPU | EVGA 1080 FTW2 Overclocked 2190Mhz | PSU | Corsair RM850i | RAM | 4x8GB Corsair Vengeance 3200MHz |MOTHERBOARD | Asus ROG Maximus X Formula | STORAGE | 2x Samsung EvO 256GB NVME  | COOLING | Hard Line Custom Loop D5 Pump Monsta 480mm Radiator  | MONITOR | Acer Predator X34 | OS | Windows 10

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×