16x vs 4x PCIe? SSD and USB 3.0

Discussion in 'Mac Pro' started by sammyman, Apr 20, 2015.

  1. sammyman macrumors 6502a

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    #1
    I'm wondering if I get an Apple SSD and put in my computer in one of the PCIe slots, will it matter if it is slot 2 or 3? Right now I have a Highpoint USB 3.0 Rocketfish in slot 2.

    I don't really understand the difference between 16x and 4x. I'm guessing I'll want the SSD in slot 2. Can anyone explain.

    Thanks
     
  2. crjackson2134 macrumors 68020

    crjackson2134

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    #2
    If you get one of the newer ssubx 512gb blades, it will only perform at half speed in Slot 2 (2.5GT/s). It should be optimal in Slot 3 (5.0GT/s).

    That said, my boot times went from 30 seconds to about 75-80 seconds. I get the blank screen for a few seconds, BONG, white screen FOR A VERY LONG TIME, then I get the Apple LOGO for about 6 seconds before hitting the loaded desktop.

    I don't think there is anyway around this for me so far. I've been asking around to find out if other users of the ssubx 512gb in Slot 3 also have excessively long cold boot times.

    Warm boot times are fun though, they are about 5-6 seconds to a fully loaded desktop. The ssubx blades are remarkably faster than any other SSD I've used, and you can feel the difference in everyday usage.

    Except for the cold boot times, you won't regret the ssubx purchase. ;)
     
  3. sammyman thread starter macrumors 6502a

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    #3
    I'm buying a 1TB Apple blade tonight (hopefully).

    I thought the faster speeds were in slot 1 and 2 (bottom two) at 16x, and the slower speeds were in 3 and 4 at 4x? Do I have this backwards? It is faster in slot 3 (2nd from the top)?
     
  4. crjackson2134 macrumors 68020

    crjackson2134

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    #4
    No I don't have it backwards. The newer ssubx doesn't initialize properly in Slot 2 and only works at 2.5GT/s when installed there. When placed in Slot 3 it will see the full 4x at 5.0GT/s. It's only a 4x card, so it won't be any faster in the 16x slot anyway even if it did manage to initialize properly. It has to do with the new controller on the SSD as far as I know.
     
  5. sammyman thread starter macrumors 6502a

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    #5
    Very interesting! I probably would have plugged it into the wrong slot and gotten frustrated thinking it needs the full 16x. I'll report back when I get all the pieces together.
     
  6. flowrider macrumors 601

    flowrider

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    #6
    All the slots are the same speed, PCIe 2.0. The difference between slots 1 & 2 and 3 & 4, is the lane width. The bottom 2 slots can carry 16 lanes of data while the top two can carry up to 4 lanes - BUT, the cards inserted in the slots must also be designed to utilize all the lanes of data to gain the full benefit of that slot.

    All video cards, AFAIK are the full 16 lanes. My Velocity x2 is only a two lane card, so no matter what slot it's in, it can only carry two lanes of data. Look at the slot connections of the three picts I have attached, the video card carries the full 16 lanes while the velocity Solo x1 carries only one and the solo x2 carries two. Notice the difference in the connectors.

    Lou
     

    Attached Files:

  7. sammyman thread starter macrumors 6502a

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    #7
    Thanks for explaining this Lou. I think I understand now.
     
  8. crjackson2134, Apr 22, 2015
    Last edited: Apr 22, 2015

    crjackson2134 macrumors 68020

    crjackson2134

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  9. Macsonic macrumors 65816

    Macsonic

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    #9
    Thanks Crjackson for sharing as this as I've learned a lot here and congrats on your new purchase. I'm also considering the SSUBX blades even though I already have the XP941. :)
     
  10. crjackson2134, Apr 22, 2015
    Last edited: Apr 24, 2015

    crjackson2134 macrumors 68020

    crjackson2134

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    #10
    Ha Ha.... I was deleting my content when you replied. I didn't want to make it confusing for anyone, so figured it might be better if he just tested it himself when the part arrives. This issue is only a problem with the newer SSUBX parts. The more common and slightly older part works fine when inserted into Slot 2. What is the cold boot like on your XP941? It's horrible for me with the SSUBX but after booted... WOW, just WOW.

    The issue is related to the fact that some slots are connected to the PCI switch and others are connected to the PCI bridge. It has nothing to do with the lane width as I understand it.

    That said, I too would prefer it to be in the 16x Slot 2 myself. You can use it there but it only works at 2.5GT/s and when I benched it, that was functionally about half speed compared to placing it into a 4x slot. It does seem backwards in a way so I understand why the OP thought it was, but there are much more issues involved than just Lane Width. The SSD controller isn't cooperating with Slot 2.

     
  11. Macsonic macrumors 65816

    Macsonic

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    #11
    Hello. With the XP941 at 256gb, for a cold boot, starting from the chime sound to the desktop, boot completes in 20 seconds. Probably from pressing the start button up to the desktop would be around 32+ seconds. If pressing the option key to reveal the hard drives, upon selecting the XP941 icon, boot gets completed in 13.5 seconds to the desktop. My XP941 is in slot 3, slot 4 is my USB 3.0 card, Caldigit. Yep, these SSD blades are snappy and fluid.
     
  12. crjackson2134, Apr 22, 2015
    Last edited: Apr 24, 2015

    crjackson2134 macrumors 68020

    crjackson2134

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    #12
    Mine is the XP951 Apple variant. I'm getting right at 1500 on BM Speedtest. It's blindingly fast once booted, but I hate the boot delay. On cold boot it's about a 60 second delay. I'm not sure if that's because of other hardware in the machine or because of having 3 different OS X boot drives. I think I'm going to pull everything out (drives/PCIe cards) and try the 951 in every slot to see if I can find a way around this boot delay.

    It's funny kind of. I did a NVRAM (PRAM) reset, re-selected the 951 as the boot drive and shut down fully. The next cold boot took the system 10 seconds. It was awesome. Sadly it didn't hold, all subsequent cold booting had a 60 second delay. Resetting PRAM again I get the one time fast boot again, then back to the delay for all others. :mad:

    Here's what I think is going on. It acts like no boot drive is selected in preferences and it's searching. I've seen this happen on spinners before when doing some OS X upgrade installs. Normally going into the settings and selecting the startup drive solves this. Now of course I have done this, but it's like it's being ignored if a cold boot is performed.
     
  13. Macsonic macrumors 65816

    Macsonic

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    #13
    My BlackMagic test is lower at around 1000 MBs for read and for write only at 800 MBs. I am on Mountain Lion but probably the slow boot is not OSX related. Hope you get to find the solution on the booting time. :cool:
     
  14. MacVidCards Suspended

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    #14
    crj,

    Sorry that your joy with PCIE SSD is being dragged down by long boot.

    Whats really odd is I have played with 6 or so of the Apple blades and 2 of the XP941s and never had that issue.

    That being said, I have never had an Apple 512GB. I have had 256 and 1GB and never seen the issue, though to be honest I didn't play with 256 much.

    One thing I would add is that some GTX980 customers had a similar issue where a PCIE SSD would confuse the system and not show a boot drive. I only saw the issue a few times and for me it would be resolved by moving PCIE SSD from 3 to 4 or from 4 to 3.

    Otherwise I have loved these drives. The response to clicks on things is like having a car with lots of hp under the hood, always eager to go.

    Much like my nMP which is a 3.7 and uses same drive, made 2009 feel like a new machine.

    The fact that you had one good boot shows it can be done. Hopefully you find the answer.
     
  15. crjackson2134, Apr 22, 2015
    Last edited: Apr 23, 2015

    crjackson2134 macrumors 68020

    crjackson2134

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    #15
    Thanks MVC,

    Tomorrow I will try Slot 4 for sure. When it is booted, this thing makes my 840 Pro feel sluggish. I really didn't expect it to have a such a seat of the pants improvement, but it does.

    Update:

    So I tried putting the SSD into Slot 4. That didn't work out at all. At first, the blade wouldn't even show up with an Option-Key boot. After rebooting a couple of times however it did. I'm still at 60+ seconds boot time however.
     
  16. ActionableMango macrumors 604

    ActionableMango

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    #16
    Have you tried booting in verbose mode? Perhaps it will be obvious which step in the boot process is being delayed. Probably not, but it's easy to do so worth a try.
     
  17. crjackson2134, Apr 24, 2015
    Last edited: Apr 24, 2015

    crjackson2134 macrumors 68020

    crjackson2134

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    #17
    No, but thanks for the idea. I'll do that tomorrow. I don't really expect this will reveal a solution however. The issue happens at the hardware/firmware level. It's like adding a piece of hardware in an older PC that needs a BIOS update in order to be recognized properly. Does verbose mode show the hardware detection process like a PC BIOS?
     

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