Pcie 3.0 x2 ssd in pcie 2.0 x4 slot

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jpe1701

jpe1701

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Mar 13, 2015
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Hi there,
So I ordered a mydigitalssd sbx 512gb pcie 3.0 x2 nvme ssd. It was on sale for $149 and my second m.2 slot only accepts pcie drives. It is a Ryzen x370 board so the second slot is pcie 2.0 x4. I am confused about how it will work. Since pcie 3.0x2 and pcie 2.0x4 use the same bandwidth will I get full speed? Or will it be halved to pcie 2.0x2?
 
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M
My suspicion is that you'll only get PCIe 2.0x2 speeds.

Even though PCIE 3.0x2 and 2.0x4 have the same bandwidth, they operate in different ways. 3.0x2 is narrow and fast, while 2.0x4 is wide and slow. If you plug an SSD that is narrow and fast into a slot that is wide and slow, the signal is going to have to operate at the lowest common denominators.

In this case, the lowest common denominator is 2.0x2.

I think a 3.0x4 in a 2.0x4 slot would operate at 2.0x4, while a 3.0x2 in a 2.0x2 will operate at 2.0x2.

But that's just my guess. I've never tested this out.
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jpe1701

jpe1701

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Mar 13, 2015
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Well my only concern is that the controller is set up to use 2 lanes so wouldn't that reduce it to pcie 2.0x2 speeds?
 
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mikewinddale

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My suspicion is that you'll only get PCIe 2.0x2 speeds.

Even though PCIE 3.0x2 and 2.0x4 have the same bandwidth, they operate in different ways. 3.0x2 is narrow and fast, while 2.0x4 is wide and slow. If you plug an SSD that is narrow and fast into a slot that is wide and slow, the signal is going to have to operate at the lowest common denominators.

In this case, the lowest common denominator is 2.0x2.

I think a 3.0x4 in a 2.0x4 slot would operate at 2.0x4, while a 3.0x2 in a 2.0x2 will operate at 2.0x2.

But that's just my guess. I've never tested this out.
 
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jpe1701

jpe1701

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Mar 13, 2015
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Old thread, but you are right. I get about 850mbps give or take. Been a while since I benchmarked it. Works good as a second drive for games, just wished I had waited until the prices dropped so much recently. Thank you.
 
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