SLI shenanigans

[MrRodmann]

Hello gurus of Linus. 

I am back with a question, this time a GPU related one and as always I'm sure I'll get the help I didn't get off the internet. So here it goes, I am trying to find out if there is a product out there that enables you to connect two PCIe 2.0 lanes into one GPU in order for me to run a GTX 1080ti without running into bandwidth bottleneck.

[AndreiArgeanu]

It's unlikely that your motherboard will run 2 pcie slots at x16 speeds and will most likely end up splitting the bandwidth in half ending with two 8x slots, basically meaning that if you had a cable connecting the two, you'd end up with the same pcie 2.0 16X slot you would have otherwise got out of a single pcie slot.

[MrRodmann]

Even if my motherboard (X58 ASUS P6T Deluxe) is rated for dual x16 lanes?

(picture from the mobo's manual)

[LIGISTX]

12 minutes ago, MrRodmann said:

Hello gurus of Linus. 

I am back with a question, this time a GPU related one and as always I'm sure I'll get the help I didn't get off the internet. So here it goes, I am trying to find out if there is a product out there that enables you to connect two PCIe 2.0 lanes into one GPU in order for me to run a GTX 1080ti without running into bandwidth bottleneck.

No, I highly doubt this would be possible.

 

But also, are you running into issues? You should be, a 16x 2.0 slot IIRC is the same as a 8x slot of 3.0.... 8x of 3.0 (thus 16 of 2.0) is plenty of bandwidth unless your doing compute application workloads.

[MrRodmann]

This mobo is what's running in my gf's pc and the 1080ti is what's in my rig atm. Given the new announcements I finally feel like the right time to upgrade which will result in said 1080ti going to that mobo. And I've read that the maximum bandwidth capacity of a PCIe 2.0 x16 lanes is 8 GB/s and that if you plug something with more than that you'll loose that performance (1080ti has 11gb of vram)

1 minute ago, LIGISTX said:

No, I highly doubt this would be possible.

 

But also, are you running into issues? You should be, a 16x 2.0 slot IIRC is the same as a 8x slot of 3.0.... 8x of 3.0 (thus 16 of 2.0) is plenty of bandwidth unless your doing compute application workloads.

 

[MrRodmann]

Granted I don't even know if the x5660 @4.2 GHz all core that is in there will bottleneck first before the missing bandwidth, but again I just wanted to know if there is such an adapting board for this purpose.

5 minutes ago, LIGISTX said:

No, I highly doubt this would be possible.

 

But also, are you running into issues? You should be, a 16x 2.0 slot IIRC is the same as a 8x slot of 3.0.... 8x of 3.0 (thus 16 of 2.0) is plenty of bandwidth unless your doing compute application workloads.

 

[LIGISTX]

3 minutes ago, MrRodmann said:

This mobo is what's running in my gf's pc and the 1080ti is what's in my rig atm. Given the new announcements I finally feel like the right time to upgrade which will result in said 1080ti going to that mobo. And I've read that the maximum bandwidth capacity of a PCIe 2.0 x16 lanes is 8 GB/s and that if you plug something with more than that you'll loose that performance (1080ti has 11gb of vram)

 

That isn't how that works. Bandwidth is stuff per time, RAM is just an amount of stuff. Your GPU isn't dumping and reloading its entire vram every second...... think about it, if it was, what in your system can even feed it that fast? Your SSD certainly can't..............

 

A 2.0 x16 slot will be plenty for gaming. Compute work where you ARE moving datasets in and out of RAM often see issues, but gaming just isn't like that; not yet anyways. Looks like 3000 series may be changing that a bit. But your 1080ti is a non issue. Yes, your CPU will likely be a bottleneck, but the PCI slot won't be

[LIGISTX]

10 minutes ago, LIGISTX said:

No, I highly doubt this would be possible.

 

But also, are you running into issues? You should be, a 16x 2.0 slot IIRC is the same as a 8x slot of 3.0.... 8x of 3.0 (thus 16 of 2.0) is plenty of bandwidth unless your doing compute application workloads.

Oops! You shouldn't be* You shouldn't be running into issues. You won't run into issues.....

 

Sorry, thats an important typo.

[MrRodmann]

Awesome! You think theres any chance theres any CPU+overclock on the LGA 1366 platform that can keep up with a 1080ti?

1 minute ago, LIGISTX said:

That isn't how that works. Bandwidth is stuff per time, RAM is just an amount of stuff. Your GPU isn't dumping and reloading its entire vram every second...... think about it, if it was, what in your system can even feed it that fast? Your SSD certainly can't..............

 

A 2.0 x16 slot will be plenty for gaming. Compute work where you ARE moving datasets in and out of RAM often see issues, but gaming just isn't like that; not yet anyways. Looks like 3000 series may be changing that a bit. But your 1080ti is a non issue. Yes, your CPU will likely be a bottleneck, but the PCI slot won't be

 

[LIGISTX]

4 minutes ago, MrRodmann said:

Awesome! You think theres any chance theres any CPU+overclock on the LGA 1366 platform that can keep up with a 1080ti?

 

No, there isn't.

 

I still have my i7 920 which did 3.82 GHz. When I got my GTX 1080 I threw it in there as a test system before my water block came in (my PC at the time was a 4770k @ 4.4 GHz I believe?), I tried doom which because of vulkan it does really well even on older stuff. At 3440x1440 I got like 70 FPS maxed out? Which was totally playable! When i got it in my 4770k system I think I jumped up to 130-150?

 

Granted, sounds like your CPU is running faster, but still. Point stands, there will be GPU performance left on the table. Is that a huge deal, thats up to you and your wallet lol. It will still be fine in all honesty. I would wait for Ryzen 4000 in a few months and maybe build a relatively cheap 4600 system. Likely cost ~400 bucks to have quite an upgrade.

[MrRodmann]

The PC in question if my gf who puts out more than plays so her PC only gets my leftovers or used parts. Not gona invest in that given the little amount of time she spends playing. But yeah, on my personal rig (i5-8600k @5.0ghz all core) I'll def upgrade the CPU part into ryzen when I get to that point. I'm just not sure what I'll upgrade first, GPU or CPU+Mobo. Specially when it doesn't seem like theres much time left (1-2 years maybe?) for DDR5 to come out, I'll prob upgrade GPU first and than wait for DDR5 and upgrade the CPU+MOBO+RAM

[MrRodmann]

4 minutes ago, LIGISTX said:

No, there isn't.

 

I still have my i7 920 which did 3.82 GHz. When I got my GTX 1080 I threw it in there as a test system before my water block came in (my PC at the time was a 4770k @ 4.4 GHz I believe?), I tried doom which because of vulkan it does really well even on older stuff. At 3440x1440 I got like 70 FPS maxed out? Which was totally playable! When i got it in my 4770k system I think I jumped up to 130-150?

 

Granted, sounds like your CPU is running faster, but still. Point stands, there will be GPU performance left on the table. Is that a huge deal, thats up to you and your wallet lol. It will still be fine in all honesty. I would wait for Ryzen 4000 in a few months and maybe build a relatively cheap 4600 system. Likely cost ~400 bucks to have quite an upgrade.

Thanks a lot though for the answers