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# USB Superspeed Peripherals

Esteemed Contributor

## Example Calculation in KBA226722

Hi, all

I would like to confirm about P of example Calculation in KBA226722 as follows:

S = 640*480*2 = 614400 bytes

F = Greatest integer less than (614400 / (16384 – 16)) = 37

P = DMA buffer size * fractional part of (S / (DMA buffer size – 16)) = 8784 bytes

However, P is:

P = 16384 * fractional part of (614400 / (16384 – 16))

= 16384 * 0.536656891495601173020527859238

= 8792.5865102639296187683284457478 bytes

The calculation does not mach. The answer is correct if (DMA buffer size – 16) instead of multiplying by "DMA buffer size".

P = (DMA buffer size – 16) * fractional part of (S / (DMA buffer size – 16))

= 16368 * 0.536656891495601173020527859238

= 8784 bytes

Which is the correct calculation for the Number of bytes in the Partial buffer?

Best Regards,

Kenshow

1 Solution
Moderator

## Re: Example Calculation in KBA226722

Hello,

Your understanding is correct. The calculation should be:

P = (DMA buffer size – 16) * fractional part of (S / (DMA buffer size – 16))

Thank you for pointing out this mistake. We will correct this mistake and update the KBA soon.

Best Regards,

Jayakrishna

Best Regards,
Jayakrishna
2 Replies
Moderator

## Re: Example Calculation in KBA226722

Hello,

Your understanding is correct. The calculation should be:

P = (DMA buffer size – 16) * fractional part of (S / (DMA buffer size – 16))

Thank you for pointing out this mistake. We will correct this mistake and update the KBA soon.

Best Regards,

Jayakrishna

Best Regards,
Jayakrishna
Esteemed Contributor