Does it matter which slot to use for SSD PCIe?

[machenryr]

I have my MacPro open and I thought I read somewhere that it matters which PCIe slot you use for the SSD blade, but I haven't been able to find this.

 

[zackkmac]

Yes, it does. Here's the config:

Slot 1 (16x) (best for GPU)

Slot 2 (16x)

Slot 3 (4x)

Slot 4 (4x)

Where Slot 1 is the bottom one (if you have the MP upright) and Slot 4 is towards the top. Use Slot 3 or 4 for best PCIe SSD performance.

 

[h9826790]

Depends on your adaptor, and cMP firmware version, and if any card installed in other slots.

 

[machenryr]

Yes, it does. Here's the config:

Slot 1 (16x) (best for GPU)

Slot 2 (16x)

Slot 3 (4x)

Slot 4 (4x)

Where Slot 1 is the bottom one (if you have the MP upright) and Slot 4 is towards the top. Use Slot 3 or 4 for best PCIe SSD performance.

LOL! Thanks! I just put it in slot 2. I had it in slot 4! LOL.

 

[h9826790]

LOL! Thanks! I just put it in slot 2. I had it in slot 4! LOL.

Slot 2 not necessary faster, but may be 50% slower if you use some simple adaptor with cMP firmware 0089.B00 or earlier.

 

[machenryr]

So I put it in slot 4.

 

[tsialex]

Yes, it does. Here's the config:

Slot 1 (16x) (best for GPU)

Slot 2 (16x)

Slot 3 (4x)

Slot 4 (4x)

Where Slot 1 is the bottom one (if you have the MP upright) and Slot 4 is towards the top. Use Slot 3 or 4 for best PCIe SSD performance.

This was correct until BootROM MP51.0089.B00. After 138.0.0.0.0 all PCIe slots are 5GT/s. Slots 3 and 4 SHARE bandwidth, if you use two demanding cards you will have contention issues.

 

[machenryr]

What?? Lol. So now you’re telling me I was right to put it in slot 2?

 

[tsialex]

What?? Lol. So now you’re telling me I was right to put it in slot 2?

if you use two demanding cards with slots 3 and 4 you will have contention issues, if you have just one, won't be a problem.

 

[machenryr]

Hm. Ok. I’ll move it. Thanks.