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Will adding a SSD on a Sata 1.5GB/s motherboard be a waste?

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August 30, 2010 11:54:47 AM

I was thinking of adding a intel solid state drive to my computer, but the SATA speed is only 1.5gb/s. Even though the Intel SSD supports 1.5gb/s and 3.0gb/s, would it be a waste? Will it still have some performance benefit?

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a c 99 G Storage
September 1, 2010 11:02:16 PM

I still think it would be worth it. It'll still be faster than a HDD, but the drive might be faster than the controller, which is what the cache is for.

I have 2 Seagate 7200.11 7200rpm 500GB drives in RAID 0, and my peak reads were only 140MBps, right below the 1.5Gb/s bandwidth. My Seagate 7200.12 7200rpm 1TB drive peaks at only over 100MBps.

Thus, SSD are much faster than any HDD. There should be a jumper you put on the SSD drive, to limit it to SATA I 1.5Gbps.
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a b å Intel
a c 415 G Storage
September 2, 2010 12:05:33 AM

The slower SATA port will limit the maximum transfer rate of the drive, but it won't hurt the drive's access time. Most of the benefit from the SSD comes from its much faster access time (about 100X faster than a hard drive) and not its transfer rate (about 2 to 4X faster).

So yes, you'll definitely still see quite a good performance improvement.
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September 2, 2010 6:59:10 AM

Best answer selected by nadesgalore.
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September 2, 2010 2:38:44 PM

Well, 1.5Gbps is 187 MB/s. This is faster than any HDD, but yes it is slower than most SSDs are capable of. Could be worth it... but if my mobo had only SATA I jacks, I would be thinking of other upgrades first.
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a b å Intel
a c 415 G Storage
September 2, 2010 9:51:27 PM

Actually 1.5Gbps is 150MByte/sec. The bit rate is a raw figure includes some protocol overhead, you have to divide by 10 to get the rate in usable data bytes/sec.
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September 2, 2010 10:32:53 PM

sminlal said:
Actually 1.5Gbps is 150MByte/sec. The bit rate is a raw figure includes some protocol overhead, you have to divide by 10 to get the rate in usable data bytes/sec.


Where is my math/understanding wrong? Isn't SATA measured in bits/s but drive speed measured in bytes/s?

1.5 gigabits = 1500 megabits = 1500000 bits = 187500 bytes = 187.5 megabytes
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a b å Intel
a c 415 G Storage
September 2, 2010 11:27:31 PM

It's true that there are 8 bits in a byte as stored in memory. But SATA uses 8b/10b encoding so it actually takes 10 bits to transmit a byte over a SATA connection.

Therefore, a SATA connection running at 1.5Gbits/sec can transmit 150MBytes/sec. It's actually even a little less than that if you take protocol overhead such as headers and checksums into account.
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September 3, 2010 2:40:55 PM

Oh, interesting. I didn't know about the 8b/10b encoding. In that case, the SSD would be bottlenecked by the connection even more in this case...

We really do need SATA III - if with protocol its less than 300 MB/s for SATA II, its pretty clear that the bottleneck is the connection for current drives.
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a b å Intel
a c 353 G Storage
September 3, 2010 3:25:24 PM

Didn't metion MB, But if you have an available pci-e to sataII card for just over 20 Bucks.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

If have an available pci-2 x4, or x8, or x16 slot you could even get the Asus U3S6 card which would add 2 USB 3 external inputs and 2 internal Sata 6 connections for 30 bucks.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Reson for providing more info about system, is MB used.
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