Discussion Don't believe all the hype about PCIe 5.0 - - - motherboards are not ready!

[foscooter]

Long post…

Just wanted to vent a little bit after a long weekend of system builds, rebuilds, research and giving up on PCI-e Gen 5.

Please don’t bash me, I know some of the issues are just a “me problem!” I know RAID is not recommended, blah, blah, blah. I did what I did to try it out. BIG FAIL!

Motherboard manufacturers are not ready for PCIe 5.0 and its full potential yet:

• There are NO Gen 5 graphics card AT ALL!
• There are some Gen 5 SSDs, only one reaches close to full speed (Crucial T705 PCIe Gen 5 NVME SSD) for PCIe 5.0
• What motherboard manufactures don’t tell you up front, but is buried in the manual(s), is something all should know:
• PCIe 5.0 is controlled by the CPU: Intel & AMD.
• When a PCIe 5.0 SSD is installed into the Gen 5 M.2 slot, the motherboard will deactivate the second PCIe onboard x16 slot.
• It will then throttle the first PCIe slot to x8 speed.

Now, some will say that you will not notice the graphics card speed difference, from x16 to x8, but that is not for me! It doesn’t matter what generation the graphics card is, they’ll all throttle to x8 speed! Not just Gen 5x8, which equals Gen 4x16, it all just x8!

If you install the Gen 5 SSD into a PCI card, it will still throttle both to x8, just like SLI or Crossfire did. Never understood why you want 2 GFX card running at half speed, instead of 1 at full speed. DRAM size?

If you want to use/install a PCIe M.2 adapter card, it’ll only run at x8 speed, regardless of slot installed in, even if it’s a PCIe 4.0 x16 slot (if your board has one, many Z790's don’t). You can only use 2xM.2 drives, even if you get a 4xM.2 card.

**EDIT** 04/10/2024:
I need to mention that the AMD x670 chipset DOES run the PCIe 5.0 slot(s) and the M.2 slot separately, so no throttling down to x8 for a graphics card. I'd post diagrams of these chipsets if I knew how to just insert an image vs a link to a url. But, in the comparisons I've read, Z790 vs. X670, Intel wins, but AMD runs cooler.
**END EDIT**

My goal for the build was this:

• Motherboard has 5 M.2 slots [Asus ROG Maximus Z790 Dark Hero]
• PCIe 5.0x4 SSD for OS [Crucial T705 2TB]
• PCIe 4.0x4 SSD for Data & Media personal folders (Documents, Downloads, Pictures, Videos) [Samsung 990 Pro 4TB]
• 2-4 PCIe 4.0x4 SSD in RAID 0 for a “Temp” drive (more on this later) [SK hynik P41 Platinum 500GB]
• 1-2GB RAMDisk for Internet cache files [DataRam RAMDisk]
• 48GB (2x24GB) DDR5-8000 RAM [G.Skill Trident Z5 RGB Series]

My final system build is this:

• Same motherboard as above
• RETURN PCIe 5.0 SSD
• PCIe 4.0x4 SSD for OS [Samsung 990 Pro 1TB] in M.2 PCIe 4.0x4 slot
• Same SSD for Data & Media as above
• Ditch the idea move moving “Temp” folder/files from original location(s).
• Not even to a RAMDisk, a whole other issue!
• 2GB RAMDisk for Internet cache files [DataRam RAMDisk]
• 48GB (2x24GB) DDR5-7200 RAM [Corsair Dominator Titanium Series]
• Overclocked to DDR-7400 in BIOS with a XMP profile provided.
• Graphics card in PCIe 5.0 slot 1, running at 4.0x16. [Asus TUF RTX 4070 Ti OC]
• 8TB SSD for backups, and a 16TB HDD to back up the backups.
• Windows 11 Pro x64 23H2

Thank for reading. I feel better…

 

[35below0]

• What motherboard manufactures don’t tell you up front, but is buried in the manual(s), is something all should know:
• PCIe 5.0 is controlled by the CPU: Intel & AMD.
• When a PCIe 5.0 SSD is installed into the Gen 5 M.2 slot, the motherboard will deactivate the second PCIe onboard x16 slot.
• It will then throttle the first PCIe slot to x8 speed.

They do "happen to mention" this. It's behind a few asterisks on the mobo main features page or the specs page.

The CPU side M.2 slot downgrades the 1st PCIe 16x slot to 8x.

Some motherboards have a second CPU M.2 slot, this one is gen 4 and does not downgrade the PCIe 16x slot. Gigabyte Aero has this feature, i don't remember which other boards do but there are a few.

When using one of the other M.2 slots, on the chipset side, sometimes the M.2 slot will disable a pair of SATA HDD/SSD ports.

This is in the fine print. It's not really false advertising. But... the BLAZING GEN 5 M.2 is front and center, while "etc. etc." details are tucked away or not mentioned. And that is not very nice.

Also never mentioned is just how little the Gen 5 matters in practical use. But it's a new feature, and a new gen so they all boast about it loudly.


Sorry you got tripped up over this. You got the right solution in the end. If the GPU matters more to you, then stick the OS drive in the chipset M.2 slot. OTOH if gaming is not a consideration, use the fastest CPU side slot.
It has to be said though, if you used a Gen 3 NVMe in any slot as your OS drive, you probably would not feel any difference.
So it's not just that the motheboards aren't ready* it's also true there are few use cases where such BLAZING transfer speeds make a difference. That may change in the future but for now, gen 3, 4, and 5 are interchangeable in most use cases.

*it's the chipset, not the motherboards. Motherboards inherit this limitation from the chipset. Intel's upcoming chipset and CPUs is said to finally remove this 16x -> 8x downgrade problem.

Edit- there are also considerable limits on RAM usage. Not only speed overall and compatibility, but also max speed limits when using 4 slots instead of 2. Esp. the budget motherboards can have severe limits.
It's all in the fine print.

 

[DSzymborski]

No, running GPUs at x8 does not make them run at "half speed" or anything close to that.

 

[thestryker]

While I can understand the frustration it could have been completely avoided just by reading the tech specs web page of the motherboard you purchased:

Expansion Slots​

Intel® CoreTM Processors (14th & 13th & 12th Gen)*
2 x PCIe 5.0 x16 slots (support x16 or x8/x8 modes)**
Intel® Z790 Chipset
1 x PCIe 4.0 x4 slot
* Please check the PCIe bifurcation table on the support site (https://www.asus.com/support/FAQ/1037507/).
** M.2_1 shares bandwidth with PCIEX16(G5)_2. When M.2_1 is enabled, PCIEX16(G5)_2 will be disabled and PCIEX16(G5)_1 will run x8 only.

Storage​

Total supports 5 x M.2 slots and 4 x SATA 6Gb/s ports*
Intel® CoreTM Processors (14th & 13th & 12th Gen)
M.2_1 slot (Key M), type 2242/2260/2280/22110 (supports PCIe 5.0 x4 mode.)**
M.2_2 slot (Key M), type 2242/2260/2280 (supports PCIe 4.0 x4 mode.)
Intel® Z790 Chipset**
M.2_3 slot (Key M), type 2242/2260/2280 (supports PCIe 4.0 x4 mode)
M.2_4 slot (Key M), type 2280 (supports PCIe 4.0 x4 mode)
M.2_5 slot (Key M), type 2280 (supports PCIe 4.0 x4 mode)
4 x SATA 6Gb/s ports
* Intel® Rapid Storage Technology supports PCIe RAID 0/1/5/10, SATA RAID 0/1/5/10.
** M.2_1 shares bandwidth with PCIEX16(G5)_2. When M.2_1 is enabled, PCIEX16(G5)_2 will be disabled and PCIEX16(G5)_1 will run x8 only.

While I agree with regards to the PCIe 5.0 M.2 implementation on current Intel platforms being dumb most video cards running x8 isn't a problem.

 

[gamerk316]

While I agree with regards to the PCIe 5.0 M.2 implementation on current Intel platforms being dumb most video cards running x8 isn't a problem.

PCIe 5.0 x8 = PCIe 4.0 x16, which isn't even close to a bottleneck yet. Heck, I saw a recent test that showed even PCIe 3.0 x16 isn't that much of a bottleneck, loosing only a handful of FPS.

 

[Eximo]

PCIe 5.0 x8 = PCIe 4.0 x16, which isn't even close to a bottleneck yet. Heck, I saw a recent test that showed even PCIe 3.0 x16 isn't that much of a bottleneck, loosing only a handful of FPS.

But there are no PCIe 5.0 GPUs so that doesn't matter at the moment, all cards will run at PCIe 4.0 8x. Well unless you count Moore Threads, but they don't really count in terms of graphics performance or compatibility.

 

[gamerk316]

But there are no PCIe 5.0 GPUs so that doesn't matter at the moment, all cards will run at PCIe 4.0 8x. Well unless you count Moore Threads, but they don't really count in terms of graphics performance or compatibility.

Unless I'm horribly mistaken how PCIe works, I'm pretty sure PCIe4 cards running on a PCIe5 slot should run at PCIe5 speeds, so in this cast PCIe5 x8 (equivalent to PCIe4 x16).

Even if the card is running at PCIe4 x8, it shouldn't be a bandwidth limitation.

 

[Eximo]

Unless I'm horribly mistaken how PCIe works, I'm pretty sure PCIe4 cards running on a PCIe5 slot should run at PCIe5 speeds, so in this cast PCIe5 x8 (equivalent to PCIe4 x16).

Even if the card is running at PCIe4 x8, it shouldn't be a bandwidth limitation.

That is not how it works.

If you put a PCIe 3.0 card into a PCIe 4.0 system it runs at 3.0. Same with storage and all other PCIe devices. You can decrease speed, but not increase it.

I agree you don't lose much performance running at PCIe 4.0 8x. I ran a PCIe 4.0 x16 card at PCIe 3.0 x16 for quite a while, makes little difference. (What I was doing was the equivalent of PCIe 4.0 8x)

 

[Colif]

If you put a PCIe 3.0 card into a PCIe 4.0 system it runs at 3.0. Same with storage and all other PCIe devices. You can decrease speed, but not increase it.

just as well really as we would otherwise have cards that only ran in certain slots, as if cards could run faster makers would lock them into slots to remove option. Cards not normally designed to run at any speed.
So it would make it harder to find a new card at cusp of a new PCIe version. That happened long ago when we swapped from AGP to PCIe to begin with... people had to upgrade entire PC as it got hard to find the old type... I was one of them. So cards only running at speed they rated makes total sense.

motherboards aren't ready for the heat of multiple pcie 5 nvme running on them. Its bad enough the cooling needed for one of them, yet alone multiple. Need to rethink layout I think.
The need for speed is over riding sense.

that and the faster the drives get, the smaller the increase between them becomes. The speed they can run isn't useful for a lot of people. It might sound good but you really not gaining a lot over one slightly slower. Bragging rights is about all.

Pcie 5 isn't a reason to buy a motherboard. Its just a feature, I wouldn't pay extra for it as you not really getting anything now.

 

[hotaru.hino]

Motherboard manufacturers are not ready for PCIe 5.0 and its full potential yet:

It's because there's really no need for this yet. But you could go "IT'S NOT ABOUT NEED, IT'S ABOUT WANT!!!!11" but every time that happens, it rarely makes sales. Like it or not, companies have to make money and slapping on an expensive interface that doesn't get a lot of sales is a hard sale.

Now, some will say that you will not notice the graphics card speed difference, from x16 to x8, but that is not for me! It doesn’t matter what generation the graphics card is, they’ll all throttle to x8 speed! Not just Gen 5x8, which equals Gen 4x16, it all just x8!

Sure it'll throttle, but are you really going to notice something like 2% less performance? (I know this is a Gen4 card, but if the best card right now loses this much performance when dropping into a previous gen slot, then we can infer the same could happen with a hypothetical Gen5 card)

If you install the Gen 5 SSD into a PCI card, it will still throttle both to x8, just like SLI or Crossfire did. Never understood why you want 2 GFX card running at half speed, instead of 1 at full speed. DRAM size?

They don't run at half speed. See the previous point.

Also unless you're shuffling around terabytes of data all the time between drives, I (and likely a lot of other people) haven't really noticed a difference in performance between SSDs since going on an SSD. I'd argue most of the "speed up" we felt wasn't from throughput, it was latency. If things feel quicker to respond, we usually care less about how long it actually takes.

 

[Eximo]

Pretty much every time I have built looking forward I have ended up regretting it. I did have PCIe 4.0 SSD and PCIe 4.0 GPU with a PCIe 3.0 CPU for a while, but I knew that would be quite short term, and now I do have PCIe 5.0, just not likely to see any use for that speed.

Nvidia has not bothered with new PCIe revisions a few times, I wonder if Blackwell will even support 5.0. SSD speeds aren't that critical as mentioned. If I have to wait 12 seconds instead of 9 for a big file to unpack or game map to load, not that big a deal. Rather have the drive longevity than rapid overheating.

 

[hotaru.hino]

Nvidia has not bothered with new PCIe revisions a few times, I wonder if Blackwell will even support 5.0. SSD speeds aren't that critical as mentioned.

I wouldn't be surprised if Blackwell is only PCIe 4.0. Or maybe if they pull off another 4090, I could see its replacement having 5.0, but the rest sticking with 4.0.

If I have to wait 12 seconds instead of 9 for a big file to unpack or game map to load, not that big a deal. Rather have the drive longevity than rapid overheating.

And even then, the big loads are infrequent. Even with a hard drive you'd probably spend more time playing the game than waiting on big loads. But if you were playing an open world game that constantly streams data, then you'd feel the pain of slow seek times.

 

[Eximo]

I wouldn't be surprised if Blackwell is only PCIe 4.0. Or maybe if they pull off another 4090, I could see its replacement having 5.0, but the rest sticking with 4.0.

That would make sense since the 4090 is in a GPU class of its own, and the price is basically whatever.

 

[foscooter]

While I can understand the frustration it could have been completely avoided just by reading the tech specs web page of the motherboard you purchased:



While I agree with regards to the PCIe 5.0 M.2 implementation on current Intel platforms being dumb most video cards running x8 isn't a problem.

Thank You, and true. I should have read deeper into the manual before purchase. We are focused on the PCIe 5.0 SSD blazing speeds, not noticing the limits of the chipset to run them.

 

[USAFRet]

We are all focused on the PCIe 5.0 SSD blazing speeds, not noticing the limits of the chipset to run them.

No, not all of us... 😱

 

[foscooter]

It's because there's really no need for this yet. But you could go "IT'S NOT ABOUT NEED, IT'S ABOUT WANT!!!!11" but every time that happens, it rarely makes sales. Like it or not, companies have to make money and slapping on an expensive interface that doesn't get a lot of sales is a hard sale.


Sure it'll throttle, but are you really going to notice something like 2% less performance? (I know this is a Gen4 card, but if the best card right now loses this much performance when dropping into a previous gen slot, then we can infer the same could happen with a hypothetical Gen5 card)


They don't run at half speed. See the previous point.

Also unless you're shuffling around terabytes of data all the time between drives, I (and likely a lot of other people) haven't really noticed a difference in performance between SSDs since going on an SSD. I'd argue most of the "speed up" we felt wasn't from throughput, it was latency. If things feel quicker to respond, we usually care less about how long it actually takes.

Thank You. Your first point is right on point! All we see are the **NEW**, not what it takes to get there.
I'll look further into PCIe *.0 x16 vs x8. I thought I noticed my video card slightly "flickering." Could have been bad connection into the slot, or bad connection to display port...

 

[foscooter]

No, not all of us... 😱

Noted. And fixed.

 

[foscooter]

Pretty much every time I have built looking forward I have ended up regretting it. I did have PCIe 4.0 SSD and PCIe 4.0 GPU with a PCIe 3.0 CPU for a while, but I knew that would be quite short term, and now I do have PCIe 5.0, just not likely to see any use for that speed.

I feel you! This is actually my 3rd Gen14 build, the other 2 were completely returned due to other problems, one returned without even opening the boxes. I have learned my lesson, in more ways than one!

 

[foscooter]

They don't run at half speed. See the previous point.

Can you elaborate? Can I have a link to anything regarding this: x16 vs x8 usages (speeds)?

 

[foscooter]

just as well really as we would otherwise have cards that only ran in certain slots, as if cards could run faster makers would lock them into slots to remove option. Cards not normally designed to run at any speed.
So it would make it harder to find a new card at cusp of a new PCIe version. That happened long ago when we swapped from AGP to PCIe to begin with... people had to upgrade entire PC as it got hard to find the old type... I was one of them. So cards only running at speed they rated makes total sense.

motherboards aren't ready for the heat of multiple pcie 5 nvme running on them. Its bad enough the cooling needed for one of them, yet alone multiple. Need to rethink layout I think.
The need for speed is over riding sense.

that and the faster the drives get, the smaller the increase between them becomes. The speed they can run isn't useful for a lot of people. It might sound good but you really not gaining a lot over one slightly slower. Bragging rights is about all.

Pcie 5 isn't a reason to buy a motherboard. Its just a feature, I wouldn't pay extra for it as you not really getting anything now.

Agreed. Lesson learned!

 

[foscooter]

They do "happen to mention" this. It's behind a few asterisks on the mobo main features page or the specs page.

The CPU side M.2 slot downgrades the 1st PCIe 16x slot to 8x.

Some motherboards have a second CPU M.2 slot, this one is gen 4 and does not downgrade the PCIe 16x slot. Gigabyte Aero has this feature, i don't remember which other boards do but there are a few.

When using one of the other M.2 slots, on the chipset side, sometimes the M.2 slot will disable a pair of SATA HDD/SSD ports.

This is in the fine print. It's not really false advertising. But... the BLAZING GEN 5 M.2 is front and center, while "etc. etc." details are tucked away or not mentioned. And that is not very nice.

Also never mentioned is just how little the Gen 5 matters in practical use. But it's a new feature, and a new gen so they all boast about it loudly.


Sorry you got tripped up over this. You got the right solution in the end. If the GPU matters more to you, then stick the OS drive in the chipset M.2 slot. OTOH if gaming is not a consideration, use the fastest CPU side slot.
It has to be said though, if you used a Gen 3 NVMe in any slot as your OS drive, you probably would not feel any difference.
So it's not just that the motheboards aren't ready* it's also true there are few use cases where such BLAZING transfer speeds make a difference. That may change in the future but for now, gen 3, 4, and 5 are interchangeable in most use cases.

*it's the chipset, not the motherboards. Motherboards inherit this limitation from the chipset. Intel's upcoming chipset and CPUs is said to finally remove this 16x -> 8x downgrade problem.

Edit- there are also considerable limits on RAM usage. Not only speed overall and compatibility, but also max speed limits when using 4 slots instead of 2. Esp. the budget motherboards can have severe limits.
It's all in the fine print.

Thank You. Your thoughtful comments are on point! It is the CHIPSET, not the motherboard! Maybe we can hope for a new chipset to handle this new technology, as it has in the past. I remember when PCIe 4.0 was new, and only AMD boards supported it. I even remember PCIe 3.0 SATA M.2 drives, and the Plextor PCIe add-on card with a M.2 drive on it. (God, I'm a nerd!)
Once again, thanks!

 

[hotaru.hino]

Can you elaborate? Can I have a link to anything regarding this: x16 vs x8 usages (speeds)?

https://www.techpowerup.com/review/nvidia-geforce-rtx-4090-pci-express-scaling/28.html

Bandwidth is the only thing that matters, which requires both the number of lanes and the PCIe gen it's running. So PCIe 4.0 x8 is effectively equivalent to PCIe 3.0 x16.

 

[foscooter]

PCIe 5.0 x8 = PCIe 4.0 x16, which isn't even close to a bottleneck yet. Heck, I saw a recent test that showed even PCIe 3.0 x16 isn't that much of a bottleneck, loosing only a handful of FPS.

However, when the motherboard throttles the PCIe 5.0 slot to x8, its x8 whether it's a PCIe 4.0 card or PCIe 3.0. Your math is correct, but doesn't apply to this tech spec.

 

[foscooter]

https://www.techpowerup.com/review/nvidia-geforce-rtx-4090-pci-express-scaling/28.html

Bandwidth is the only thing that matters, which requires both the number of lanes and the PCIe gen it's running. So PCIe 4.0 x8 is effectively equivalent to PCIe 3.0 x16.

Okay, I did see that post, but misread it! Go figure. I looked deeper into the display specs, and now see what you are saying: PCIe 3.0 x16 | 4.0 x8 are "equal." Thank You!

 

[foscooter]

Unless I'm horribly mistaken how PCIe works, I'm pretty sure PCIe4 cards running on a PCIe5 slot should run at PCIe5 speeds, so in this cast PCIe5 x8 (equivalent to PCIe4 x16).

Even if the card is running at PCIe4 x8, it shouldn't be a bandwidth limitation.

I'm sorry, but that's like saying a PCIe 3.0 x4 SSD in a PCIe 4.0 x4 M.2 slot will run at "4" speeds. The interface will run at "4" speeds, but the drive is limited to "3" speeds. Wouldn't this be the same for a graphics card? Just asking.