Surprising AHCI vs IDE speed

[j7n]

I have read mixed opinions about the mode of the disk controller. The prevailing thought is it makes no or very little difference in practice outside of synthetic tests. The IDE compatibility mode came first and works with more software.

But here I have a computer with an Intel H77 PCH (Intel DH77KC) with a Western Digital WDS120G1G0A-00SS50. It is connected to a SATA 6G port. When the computer is in IDE mode set in BIOS, the speed to this memory drive is about 3 MB/s (three megabytes). In AHCI mode it is normal over 100 MB/s. When I saw this, I though the drive was broken. Another SSD is connected to a SATA 3 gigabit port and works normally. I can't swap them now to further investigate because of tight cable management.

[D.Draker]

13 hours ago, j7n said:

When the computer is in IDE mode set in BIOS, the speed to this memory drive is about 3 MB/s (three megabytes).

You wanted to say Mbit, maybe?

[D.Draker]

13 hours ago, j7n said:

Intel DH77KC

Odd, bad BIOS, or a broken board? Last time I remember the AHCI mode worked better with LGA775 boards in 2006-2007.

[Klemper]

Did you try another cable?

[j7n]

Yes, I switched to another cable to get an L-connector. It works fine in AHCI mode, which I would try to use anyway. Something is very suboptimal in the "translation" stage. I opened the disk in WinHex and it was obviously laggy when dragging the scrollbar, and the read speed in HDTune was only 3 MB/s. I've since put 3 Windows on it.