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Allistah

macrumors 6502
Original poster
Apr 19, 2019
254
80
Bay Area, CA
Does anyone know what type of SATA cable comes stock in the mid-2011 27" iMac? Is it a SATA 2 or SATA 3 cable?
 
There are three SATA ports. One for the hard drive, one for the optical drive and another for a SSD placed under the optical drive.

Originally these were limited to SATA II (3Gbps) on all ports but a firmware update enabled SATA III (6Gbps) for the HDD and SSD positions. The optical drive port is limited to SATA II (3Gbps). So if you want three SSDs installed then you should get a SATA II SSD to replace the optical drive.

If your Mac didn’t come with the SSD slot then it wouldn’t come with the SATA cable for that port but one can be attached.
 
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I have the optical drive without the SSD slot. This iMac had a standard 7200 rpm SATA hard drive in it when it was bought. Do you know if that stock cable for the mechanical hard drive is SATA2 or 3?

If SATA2, do you think that running a SATA3 SSD drive on that stock cable with a negotiated speed of 6G would exhibit this type of problem? See the first post for what the transfer speeds look like in the graph.
 
Your Mac can have up to three SSDs installed.

Take a look at the ifixit guide or OWC install videos.

The cable for the HDD is a SATA III one.

Replacing the hard drive is much more straightforward than replacing the optical drive or placing a SSD under the optical drive

An alternative is to boot off an external SSD. This Mac only has USB2, so using the Thunderbolt port would be the way to go for this.
 
I’m trying to troubleshoot fast/slow ssd problems, not looking to add drives. I’ve had the whole thing apart many times during video card, WiFi, and BT upgrades so don’t need any guides.

Was trying to find out if the stock cable is a sata3 cable or not and if the problem I am presenting could be due to a cable issue or not.
 
I’m trying to troubleshoot fast/slow ssd problems, not looking to add drives. I’ve had the whole thing apart many times during video card, WiFi, and BT upgrades so don’t need any guides.

Was trying to find out if the stock cable is a sata3 cable or not and if the problem I am presenting could be due to a cable issue or not.

There is only one type of SATA cable, which can be used for SATA I, II or III.
SATA cables are passive, i.e they have only wires and connectors, no other IC inside.
Bad cables or bad connectors may some times result in lower transmission speed, but not very likely.
Replug the cable may solve your problems. It solved my similar problem once. (Cable not tightly fit to the SATA socket/power socket on the drive)
 
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I’m trying to troubleshoot fast/slow ssd problems, not looking to add drives. I’ve had the whole thing apart many times during video card, WiFi, and BT upgrades so don’t need any guides.

Was trying to find out if the stock cable is a sata3 cable or not and if the problem I am presenting could be due to a cable issue or not.
Edit: The original Apple cable is a bunch of individual wires, but so far it works fine with SATA3 speed.
The power feed to the HDD is just a bunch of cable. The data part is actually properly shielded SATA cable. Since the individual pairs are shielded, it should wirk fine with SATA 3 speeds, and I have not heard of problems so far. (End of edit).

You can however easily replace it with a proper shielded type of cable. If you suspect any problem here, replace the cable with a shielded one and see whether this fixes your problem.
 
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I replaced the cable last night and it did not solve the problem. The issue must be in the drive so I have a new drive coming. The issue shows up in High Sierra, Mojave, and Big Sur so the OS version or actual OS install doesn't matter. This further supports the issue is in the drive.

I did find out in another thread that this drive has an estimated life of about 100 TBW. Somehow after only 4 months of light use, it has about 218 TBW. No idea how that happened but I'm going with a Samsung 860 EVO 1TB drive this time. Once I get that new drive and can confirm the issue is really fixed, I'll report back. (Won't be until the weekend)
 
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