Subject: RE: On PDFs
From: "Miller, Alan" <Alan -dot- Miller -at- prometric -dot- com>
To: "TECHWR-L" <techwr-l -at- lists -dot- raycomm -dot- com>
Date: Fri, 25 Apr 2003 08:29:31 -0400

Oops. You're absolutely correct. I screwed up. My apologies.

In the joy of actually having a calculation to fool around with, I let my brain slip into idle and let my fingers do the thinking. No. Wait. It was the calculator's fault. Yeah. That's it. The calculator did it. :-{)

Al Miller
"Chief Documentation Curmudgeon"
Prometric, Inc., a part of The Thomson Corporation
Baltimore, Maryland

A lie gets halfway around the world before the truth has a chance to get its pants on.
-- Sir Winston Churchill

-----Original Message-----
From: Dick Margulis [mailto:margulis -at- mail -dot- fiam -dot- net]
Sent: Thu 4/24/2003 4:32 PM
To: TECHWR-L; Miller, Alan
Subject: RE: On PDFs

Whoa there, Alan! You're a cuppa coffee short this afternoon. Kbps is kiloBITS per second, not kiloBYTES per second.

Let's start over. 1 KB = 1,024 bytes = 8,192 bits. MIME encoding blows that up by a factor of about 1.5 for reasons not entirely clear to me, so call it 12,000 bits. At 56 Kbps, that's a little over 0.2 s per KB or about 3 m per MB.

Or did I screw up, too?


"Miller, Alan" <Alan -dot- Miller -at- prometric -dot- com> wrote:

>rbilbao -at- us -dot- amadeus -dot- net asked:
>>>Does anyone know where I can get some cold hard facts about PDF download times?<<
>Easy question. <Rhetorical question>So how come nobody's answered it yet?</Rhetorical question> The answer is: "In your calculator." :-{) Use this simple formula:
>File size (bytes) / Transfer rate (bytes per second) = Time for transfer (seconds)
>If your file size is given in kb, multiply by 1024 to get bytes (a kb is *not* 1000 bytes; it's 2^10 bytes, or 1024). Likewise, multiply Mb by 1,048,576 to get bytes (a Mb is 2^20). Then, divide by the transfer rate (56,000 bytes per second; this time kbps *is* 1000 bytes per second).
>If you have a 1 kb (1024 bytes) file to download at 56 kbps, you get:
>1024 bytes / 56,000 bytes/s = 19 s (rounded to two significant digits, the lowest precision of my input numbers)
>Hmmm. Looks like a thumb-rule to me: 1 kb at 56 kbps = 19 s
>If you want minutes, divide by 60; for hours, divide by 3600.

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