Baud Time/Speed/Size Conversions?

[Flack]

Does anyone know or have a list of how long a program would take to download depending on baud rate?

What I want to do is something like, oh, a 3 meg MP3. How long would that have taken to download at 300 or 1200 baud? Does anyone know how to convert those rates?

[sniperCCJVQ]

http://www.onlineconversion.com/downloadspeed.htm

[Gapporin]

According to the above link, it would take you about 7.5 minutes to download a 3MB file. And a 56k modem is 187 times faster than a 300 baud modem. Do the math:

7.5 x 187 = 1402.5 minutes or 23.375 hours. Yikes.

What about a 1200 baud modem? A 56k modem is 46.75 times faster than a 1200 baud modem. So, here's how it adds up:

7.5 x 46.75 = 350.625 minutes or 5.84 hours.

Hope this helps!

EDIT: Didn't realize you wanted a program. Whoops.

[Flack]

Nope, the website is completely fine. What I'm not sure of is if, for example, 28.8k is exactly half of 56k. The only thing I can compare that to is CD burners -- I know that 52x isn't 52 time faster than a 1x burner. A 1x burner burns a CD in "real time", or basically 70 minutes. I'm pretty sure a 52x burner doesn't burn a full, 700meg CD in a minute and twenty seconds. This could be completely unrelated and comparing apples to oranges, but I'm just using it as an example.

The reason I'm trying to do this is I'm trying to figure out how long it used to take me to download a complete Commodore 64 disk. One side of a C64 disk is basically 180k. Rounding up and using the above math, that figures to approximate 1.5 hours to download one 180k. Maybe I'm wrong, but it seems like it used to take longer than that. That could be a time perception issue rather than a technical one, admittedly. ;)

I'm pretty sure I remember that while downloading at 1200 baud it took me approximately 30 minutes per side. That would convert down to around 2 hours per side at 300 baud, which sounds closer to being accurate. I guess it could also have something to do with using different protocols and having different error checking routines back then.

[davidbrit2]

Well, okay, assuming you're using the XModem protocol (http://www.commonsoftinc.com/Babylon_Cpp/Documentation/Res/XmodemProtocol.htm), you'll have 4 bytes overhead for every 128 bytes. And then the receiver will send a 1-byte acknowledgment for every block. So round up to the nearest 128, and multiply by 133/128 to get the actual amount of data transfer.

Once you've done that, you can then multiply by (8 bits/1 byte) * (1 sec/x bits) substituting the proper baud rate for x. This of course assumes two things: the modem itself isn't using any of its throughput for hardware error correction, and no blocks have to be to be resent due to errors. The former is a definite possibility, but the latter is a bit less likely, so your calculation will probably be a slight underestimate.

[Flack]

School for me started at 8am and lunch was at 11am. Also, most BBSs would let you idle for 30 minutes before hanging up on you. I remember distinctly starting downloads right before leaving for school, driving home during lunch to flip the disk over and still being online, and then coming home after school to play my new games. That would put downloading one side of a disk somewhere between 2.5 and 3 hours, which I guess would be possible with Xmodem (although Punter would be more likely).

2 hours is a close enough ballpark though. I laughed when I read that it would take over a day to download an MP3 back then at 300 baud. Of course speed wouldn't have been the only problem -- storing one 5 meg MP3 on single sided floppies would have taken 28 diskettes!