Concepts : Speed, Width & Capacity

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Musings by Genisys Consultant, Nigel

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Speed, Width & Capacity:-

Just a few years ago I remember it being said that there was no way that microprocessor chips could exceed 100Mhz (100 million cycles per second) - because molecules just couldn't move any faster. Now 2.8 Gigahertz units are available and even affordable for the home.

Two Thousand Eight Hundred Million Cycles per second !

This is not to indicate that I'm easily awed, but have in mind that the input and output have to keep in step: Any delay that's not anticipated - say from a cold or sluggish(?) memory cell, has to result in the occasional 'dropped stitch'. 

Be not surprised they occasionally get it wrong… Be more surprised they ever work at all !


To debate the speed of electrical impulses going down a cable is close to arguing about the speed of light… it's actually quite constant. However, the clarity of the signal (accepting there can be 'noise', 'echo' and 'cross-talk' etc. on the line), determines how tight the impulses can be packed in and still arrive uncorrupted at the other end. Hence, 'Bandwidth' refers to the rate at which intelligible data can be transferred - and it's usually quoted in bits per second.

With the development of electronic filters and 'line-conditioning', it's currently practical to push up to 8Mhz through an ordinary telephone line, whereas, using high quality copper cable or fibre optics - an office network can be run at 1Ghz… like 125 times as fast. However, todays 'Norms' are 500Khz (ADSL/Broadband) and Fast Ethernet (100Mhz).

The relevance of this is that there's absolutely no problem pushing - say 25 Megabytes around the office, but it's VERY tedious trying to get the same amount down the phone line.

Just as a speculative example… It should take approximately 11 hours to send the contents of a full CD by Broadband. (Note that the upload speed is different to the download speed - (Asynchronous) This is because both run on a single circuit and there has to be some way of identifying what's coming from what's going. The internal office network uses separate transmit & receive circuits - effectively a dual carriageway, so it doesn't have the same problem).

Perhaps an easier way to grasp this in more tangible terms is to think of weight ( 1 Megabyte = 1 ton ), and Road-width ( 1 Mbps = 1 foot )… 25 Tons ( an articulated lorry load ) will have no trouble on a one-way 100ft wide road, but to get it down a six inch wide path - you can't even use a wheelbarrow - and there's stuff coming the other way!

Size / Capacity :- 

Bits, Bytes, Kilobytes and so on through to Exabytes are listed in the Glossary.

Each of the systems we use as servers could probably hold all of the text of all human writings up to the advent of the printing press.

Collectively, all our systems ( circa 1 Terabyte ), would hold a copy of everything written and printed up to around 1900.

Nobody knows how much information is on the Internet - it goes up in Exabytes daily, most of it readily available - on your desktop. 

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