How many bits is written at a time to my drive?

Hello everyone Happy

Whenever I make an action, save, change etc. a file:

How many bits is written by the writing-head to my HDD at a time?
Does it write several bits simultaneously, or only one bit at a time, until the whole action is written?

I have the same questions for SSD and the flash-memory function?

I have only been able to find something about writing speed

Thanks a lot in advance for answering

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Re: bits

Well, IDE (PATA) has an interface with 16 parallel bits (see, while SATA has a serial interface. But that doesn't say anything about the structure of the head (could be serial or parallel) or the way the bits on the flash-sticks are written. Consider that internal and device dependent, then you're probably right.

It's only important for the electronic engineers that design the lowest level of chips.

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I'm going with "one". Why?
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Re: one

On a magnetic tape (the good old 800 or 1600 bpi variant) it were 8 in parallel. Maybe even 9, for an extra parity bit.

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And going back further.

In magnetic core memory the usual array could only flip one bit at a time.

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Go back a little further

One inch tape....14 bits across..written parallel.....high tech stuff.

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That beats even the punch card
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Punch cards....paper tape....memory that was a bunch of wired doughnuts.

We have come a long way.

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So the final conclusion is, that on HDD only one bit is written at a time?

And how many bits at a time on SSD?

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One again. Why?

Look at the SATA interface and it's serial.

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Documentation for SATA


Just serial so not exactly a parallel write. At some point in the drive there is a buffer so a page or sector of flash is re-written but that mechanism is not exposed to us. But as the interface is serial, we can say it's written a bit at a time.

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