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ASRock Z390 Taichi Ultimate PCIe lanes

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CGR View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CGR Quote  Post ReplyReply Direct Link To This Post Topic: ASRock Z390 Taichi Ultimate PCIe lanes
    Posted: 25 Jul 2021 at 10:20pm
Good day,

I wonder if someone could explain why when using all 3 PCIe x 16 slots that the middle slot reduces to X 4 lanes.

Top & middle lanes supplied by CPU 16 lanes which gives top slot X 16 or if top & middle slot used gives two X 8.

The lower slot is maximum x 4 lanes which are supplied from the chipset.

My question is why, if all 3 PCIe x 16 slots are used, the lane count becomes 16 / 4 / 4.

By using the lower slot at X4 (supplied from the chipset), the middle slot normally X8 has been reduced to X4, why has this happened.

Most motherboards with a similar configuration of PCIe slots have 8/8/4 available, whereas the ASRock Z390 Taichi Ultimate seems to be 8/4/4.

Than you in advance for any info on this.

Regards
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CGR Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jul 2021 at 10:22pm
Good day,

Apologies.

Error in first post.

Should read.

My question is why, if all 3 PCIe x 16 slots are used, the lane count becomes 8 / 4 / 4.

Regards
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ASRock_TSD Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jul 2021 at 4:47pm
Hi CGR,

Thank you for your post.

To match the NVidia 3 ways SLI requirement, all PCIe slots should connect to the CPU directly.

This is the reason why Z390 Taichi Ultimate gets x8/x4/x4 at Triple GPUs setup.

The motherboard which has x8/x8/x4 can only support NVidia 2 ways SLI because the PCIe x4 slot is provided by the chipset.

If you have other questions, please feel free to contact us.

All the best,
ASRock TSD
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CGR Quote  Post ReplyReply Direct Link To This Post Posted: 28 Jul 2021 at 6:31am
Good day,

Thank you very much for the reply.

Correct me if I am wrong, however, I was under the impression that to allow/enable SLI a minimum of X8 PCIe lanes were required on each slot in 2 way or 3 way etc.

Therefore, the Z390 Taichi Ultimate would not be able to qualify/enable 3 way Sli due to only X4 PCIe lanes on 2nd & 3rd slots (even if a switch has made all of these connected to the CPU).

Also when the X8 PCIe lanes from CPU on the 2nd slot are switched to give X4 PCIe lanes from CPU on 2nd & 3rd slots, what happens to the X4 PCIe lanes from chipset that were previously allocated to the 3rd slot.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote ASRock_TSD Quote  Post ReplyReply Direct Link To This Post Posted: 03 Aug 2021 at 5:10pm
Hi CGR,

Thank you for your reply.

After checking, all three PCIe x16 slots are connected to CPU and will run x8/x4/x4 at triple GPU setup.

This design can get the better efficiency of the 3-way crossfire setup.

All the best,
ASRock TSD
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CGR Quote  Post ReplyReply Direct Link To This Post Posted: 04 Aug 2021 at 5:59am
Good day,

Again, this reply does not seem to make sense.

If indeed the 3rd PCIe X 16 slot is supplied with 4 PCIe lanes by the CPU, how is it possible that this board can also offer x16/x0/x4 configuration for the three PCIe slots. If the 3rd slot is also supplied by the CPU, then that is 20 PCIe lanes from the CPU which are not available, only 16 PCIe lanes are available from the CPU.

It seems from my research on this, that the 3rd PCIe slot is supplied from the chipset, at least when using 1st & 3rd PCIe slots in x16/x0/x4 configuration, which would be 16 lanes from CPU and 4 lanes from chipset.

So the question is, why, when most other similar boards use the CPU 16 lanes as X8/X8 in the first 2 PCIe slots, does the Taichi Ultimate board use a different configuration of x8/x4/x4, as it appears (at least in the x16/x0/x4 configuration) that the 3rd slot is supplied 4 lanes from the chipset, does this mean that in the 3 PCIe slot configuration that the 3rd slot supply of 4 lanes is switched from the chipset to the CPU

If so, why, other similar boards have x8/x8/x4 PCIe slot configuration for 3 way crossfire.

Please note that both replies up to now do not make any sense.

Regards
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ASRock_TSD Quote  Post ReplyReply Direct Link To This Post Posted: 06 Aug 2021 at 6:23pm
Hi CGR,

Thank you for your reply.

All three PCIe x16 slots are connected to the CPU and will run x8/x4/x4 at a triple GPU setup.

When you plug the PCIe devices on PCIE2 and PCIE5, the motherboard will run at triple GPU mode and run at x8/x0/x4.

All the best,
ASRock TSD
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