There are several and various reasons that cause the low performance of an SSD. We’ve addressed the most common of them HERE. One of them was using the standard IDE mode instead of AHCI with an SSD.
In this article we will be discussing AHCI mode, what it means and what performance advantages it can provide to your overall system that runs an SSD.
What Is AHCI Mode?
AHCI stands for Advance Host Controller Interface.
The Advanced Host Controller Interface (AHCI) specification describes the register-level interface for a host controller for Serial ATA. The specification includes a description of the interface between system software and the host controller hardware. In other words it is a hardware mechanism that allows software to communicate with Serial ATA (SATA) devices (such as host bus adapters) that are designed to offer features not offered by Parallel ATA (PATA) controllers, such as hot-plugging and native command queuing (NCQ).
Many SATA controllers can enable AHCI either separately or in conjunction with RAID support. AHCI is fully supported out of the box for Microsoft Windows Vista, 7 & 8. Older versions of Windows require drivers written by the host bus adapter vendor in order to support AHCI.
Advantages Of AHCI
SSDs boast incredibly fast response times. So, they realize their best performance when fielding multiple commands simultaneously, consequently benefiting from the parallelism that defines most SSD architectures. This is precisely the reason we see better benchmark performance when we use queue depths of up to 32 versus a queue depth of one.
AHCI supports NCQ allowing SATA drives to accept more than one command at a time and dynamically reorder the commands for maximum efficiency.
Another benefit of it is that it supports hotplugging of devices.
Spinning hard disk drives also benefit from AHCI mode as it supports staggered spin ups of multiple hard drives at boot time.
Enabling AHCI Mode
To avoid any potential hassle it’s always recommended that you enable AHCI mode while your SSD is empty, and do a clean install of the operating system on your new drive instead of using the migration procedure that might cause some errors to the overall functionality of your system. But rest assured that even if you got your Windows on your SSD before enabling AHCI mode you will find here a solution.
Enabling AHCI Before Windows Installation:
To do this: In the system BIOS, set the SATA controller for Advanced Host Controller Interface (AHCI) operation before installing Windows. This step is crucial. Using the legacy IDE or ATA mode prevents you from installing the proper disk controller driver later and will result in reduced performance.
After installing your operating system you need to verify the SATA controller is set to AHCI Mode. We will work here on Windows 7 as an example:
- On the Start menu, select Control Panel.
- Double-click ‘System’ from the Classic View (or the small or large icon view in Microsoft Windows 7).
- Select ‘Device Manager’ in the left pane.
- From the Device Manager, look for an entry named IDE ATA/ATAPI controllers.
If this entry is present, expand it and look for one of the controllers to list AHCI.
- If an AHCI controller is identified, then the system is in AHCI mode.
- If none of the controllers above are shown, then your system is not in AHCI mode.
Enabling AHCI After Windows Installation:
If you already installed your operating system in legacy IDE mode, try to follow these steps:
1. Startup “Regedit
2. Open HKEY_LOCAL_MAHCINE / SYSTEM / CurrentControlset / Services
3. Open msahci
4. In the right field left click on “start” and go to Modify
5. In the value Data field enter “0” and click “ok”
6. exit “Regedit”
7. Reboot Rig and enter BIOS and enable AHCI mode as laid out above.
Or just watch this video and follow up:
It is recommended to switch to AHCI after completing the steps listed in this Windows Article: http://support.microsoft.com/kb/922976, providing your platform supports AHCI.”
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