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CompTIA A+ Certification All-in-One Exam Guide

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NVMe

AHCI was designed for spinning SATA drives to optimize read performance

as well as to effect hot-swappability. As a configuration setting, it works for

many SSDs as well, but it’s not optimal. That’s because for an SSD to work

with the operating system, the SSD has to include some circuitry that the OS

can see that makes the SSD appear to be a traditional spinning drive. Once a

read or write operation is commenced, the virtual drive circuits pass the

operation through a translator in the SSD that maps the true inner guts of the

SSD.

The Non-Volatile Memory Express (NVMe) specification supports a

communication connection between the operating system and the SSD

directly through a PCIe bus lane, reducing latency and taking full advantage

of the wicked-fast speeds of high-end SSDs (see Figure 8-16). NVMe SSDs

come in a couple of formats, such as an add-on expansion card, though most

commonly in M.2 format. NVMe drives are more expensive than other SSDs,

but offer much higher speeds. NVMe drives use SATAe.

Figure 8-16 NVMe enables direct-to-the-bus communication.

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