Gen 4 SSD on Gen 3 slots
 
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yesornofei
(@yesornofei)
Active Member
Joined: 2 years ago
 

Hi, I have a 2018 Mac mini and a Thunderbolt3 NVME SSD enclosure,

I notice that the Gen 4 NVME SSD is getting cheaper and cheaper, I was wondering if one day some Gen 4 NVME SSDs will be cheaper than some of the expensive models of Gen 3 SSD(Samsung 970 Pro for example),

and did anyone test how the speed decrease in Gen3 slot(in my case, a thunderbolt 3 enclosure)

let 5GB/s be the GEN4 SSD read speed, what speed will it be in a GEN3 slot?

will it be the Max speed of gen3 which is about 3.5GB/s, or will it be 2.5GB/s because the bandwidth is half-off?

Did anybody tried and know the real answer?

This topic was modified 5 months ago

mac mini 2018 i7 egpu with RX580


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itsage
(@itsage)
Founder Admin
Joined: 4 years ago
 

@yesornofei, Thunderbolt 3 bandwidth throughput is capped at 22Gbps. PCIe 4.0 NVMe drives in a TB3 enclosure work but they don't go faster than this cap.

 

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yesornofei
(@yesornofei)
Active Member
Joined: 2 years ago
 

@itsage, Thanks, I will avoid the expensive 3500MB read speed NVME SSD to save some money, as only 22Gbps=2750 MB/s is capped by Thunderbolt 3.

 

mac mini 2018 i7 egpu with RX580


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joevt
(@joevt)
Noble Member
Joined: 4 years ago
 

It's hard to find PCIe 3.0 NVMe drives that can cap the write speed of Thunderbolt NVMe enclosure. Or maybe all my PCIe 3.0 NVMe drives are old...

Here's a test with a Sabrent Rocket NVMe 4.0 2TB using AJA System Test Lite in Big Sur on a Mac mini 2018:

Sabrent Rocket NVMe 4.0 2TB with Trebleet NVMe Thunderbolt enclosure (Alpine Ridge based) read/wite MB/s: 2607/2640

Kind of interesting that write is faster than read in this case.

Here's some tests in Catalina with different PCIe 3.0 NVMe drives:
 #2 

 

Mac mini (2018), Mac Pro (Early 2008), MacBook Pro (Retina, 15-inch, Mid 2015), GA-Z170X-Gaming 7, Sapphire Pulse Radeon RX 580 8GB GDDR5, Sonnet Echo Express III-D, Trebleet Thunderbolt 3 to NVMe M.2 case


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