 |
|
|
|
|
|
| |
| |
|
|
|
|
| |
| |
|
|
>> I found the following quote on Wikipedia:
>>
>> "The theoretical capacity of a Boeing 747 filled with Blu-Ray discs is
>> 595,520,000 Gigabits, resulting in a 37,034.826 Gb/s flight from New
>> York to Los Angeles."
>>
>> Somebody bothered to compute this?!? o_O
>
> Or as a uni lecturer said to my data comms class (circa mid 1980's):
>
> "Never underestimate the bandwidth of a ute full of tapes speeding down
> the highway"
Heh, yeah!
> At the time we were learning about synchronous protocols operating over
> 1200bps links.
I wonder... What's the bandwidth of a punch-card reader/writer?
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
> Out of idle curiosity: have you actually measured data-transfer?
Several times, just last night I tried the BBC iPlayer diagnostic page and
it gave me 5.8 Mbit/s. In my modem settings page it says it's connected at
60xx kbit/s usually. Sometimes download speeds in windows go up to 600
Kbyte/s, it depends on where it's coming from. I guess the theoretical
limit of my line might be 6 Mbit/s, but it would be a coincidence as my
package is only for 6 Mbit/s.
> I pay for 6Mbit/s but get only 3Mbit/s.
That's like my dad, he pays for 8Mbit/s (AFAIK all BT packages in the UK
offer 8Mbit/s) and only gets about 2.5 (according to the modem settings
page).
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
>> I pay for 6Mbit/s but get only 3Mbit/s.
>
> That's like my dad, he pays for 8Mbit/s (AFAIK all BT packages in the UK
> offer 8Mbit/s) and only gets about 2.5 (according to the modem settings
> page).
Presumably the link-layer speed depends on the line. (AFAIK, a large
part of the modem handshake process consists of testing the various
frequency bands to see which ones are clear enough to be useable. That's
what dictates your transfer speed.)
The amount of IP data you can transfer depends not only on the
link-layer speed, but also the speed of the server you're talking to,
how much congestion there is on the entire route between you and the
server, how responsive your own PC is going, etc etc etc.
(And, of course, the amount of "real" data is the amount of IP data
minus all the protocol overhead - IP headers, TCP headers, handshakes,
retransmits, timeouts, etc.)
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
TC wrote:
> God, how I hate advertisements with "up to" or "starting from"...
I always liked "Up to 50% off, or more!"
--
Darren New, San Diego CA, USA (PST)
Linux: Now bringing the quality and usability of
open source desktop apps to your personal electronics.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Invisible wrote:
> I wonder... What's the bandwidth of a punch-card reader/writer?
Readers ran somewhere between 100 and 150 cards per minute, depending on how
much you paid for them. Roughly 80 bytes per card.
--
Darren New, San Diego CA, USA (PST)
Linux: Now bringing the quality and usability of
open source desktop apps to your personal electronics.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 1/05/2010 12:07 AM, Invisible wrote:
> I wonder... What's the bandwidth of a punch-card reader/writer?
Good question but I'm afraid I don't know off hand.
Suppose an 80 column card with 10 bits/column. That is 800 bits per
card. Maybe 20 cards per second through a reader ? Could be higher
since those things were really impressive bits of engineering.
Something like 16K bps ?
Now cards were not generally used for arbitrary data. For example in
many cases cols 73-80 were used for card sequence numbers. Data was
often characters so only 6 or 7 bits of variability for most characters.
Then the readers have to be fed.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Paul Fuller wrote:
> Suppose an 80 column card with 10 bits/column. That is 800 bits per
> card.
No. If you punched all the holes out of the card (a so-called 'lace card'),
it wouldn't go thru the reader. It was 7 or 8 bits per column. Even binary
punched on the card was spread out so it wouldn't make too many holes.
> Maybe 20 cards per second through a reader ? Could be higher
> since those things were really impressive bits of engineering.
Some of them were very fast. Most were closer to 5 or 10, unless you had a
really high-end giant machine.
--
Darren New, San Diego CA, USA (PST)
Linux: Now bringing the quality and usability of
open source desktop apps to your personal electronics.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
>> Suppose an 80 column card with 10 bits/column. That is 800 bits per
>> card.
>
> No. If you punched all the holes out of the card (a so-called 'lace
> card'), it wouldn't go thru the reader. It was 7 or 8 bits per column.
> Even binary punched on the card was spread out so it wouldn't make too
> many holes.
>
>> Maybe 20 cards per second through a reader ? Could be higher since
>> those things were really impressive bits of engineering.
>
> Some of them were very fast. Most were closer to 5 or 10, unless you had
> a really high-end giant machine.
Ah, the wonders of the Internet. Ask any weird-arse question, and
*somebody* will know the answer! :-D
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Orchid XP v8 wrote:
> Ah, the wonders of the Internet. Ask any weird-arse question, and
> *somebody* will know the answer! :-D
Thinking on it, the difference was speed. Was it a mechanical card reader or
an optical card reader. Did it shine light thru the holes? Then you could
slide a stack of cards past pretty much as fast as you want, which was good
if you had a giant IBM or something and you wanted to do lots of processing.
Otherwise, it was cheaper to build a mechanical reader, with pins that would
complete circuits thru the holes in the card, which obviously meant moving
the cards slower. If your machine was sufficiently slow, there was no point
in having a faster card-reader. I only worked with the slow ones.
--
Darren New, San Diego CA, USA (PST)
Linux: Now bringing the quality and usability of
open source desktop apps to your personal electronics.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
> My employer's Internet connection is *guaranteed* to be 5 Mbit/sec in both
> directions at all times. (There are also contractual guarantees about how
> quickly the ISP will fix it if it breaks.)
>
>
> How much do you pay for your broadband?
Ouch!
IF you are lucky enough to dwell at a convenient location and get VDSL, then
you pay with t-com about 600 EUR/year for 25-50 Mbit/s downstream / 2.7-10
Mbit/s upstream, including a phone-flat and a few (for me) uninteresting
TV-programs.
If you want just 6Mbit/s - .5 Mbit/s and a phone-flat you pay about 468 EUR.
However, nobody here expands into rural areas. The reason is simple: if you
are in communications and invest into infrastructure, our laws force the
companies to "open" their lines to competitors at very cheap rates. So new
cables are only places below surface where they can be reasonably sure that
enough customers will stay with them to make it worth their while. That is
only the case where many people are crammed into very small spaces, like the
large cities. Free markets are not always good...
If you can only get ISDN (128 kbit) things get expensive - the worse the
line, the more you pay. Then you pay about 100 EUR/month (to my best
knowledge). Absurd.
In the worst locations here to get a 5 Mbit/5Mbit line you would have to
bundle 40 ISDN connections, so you would have to pay around 48.000 EUR /
year. Probably you could get this cheaper with other telcos.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
