Thursday, 1 December 2011

it was 30 years ago today

that Acorn Computers launched the BBC micro.

I got a model B Beeb while I was doing my PhD, and had great fun learning to program.  (I already knew Fortran IV, but until reading Structured Programming with BBC Basic, I hacked, rather than programmed.)  I used my Beeb to do some real science (see the acknowledment section on p544), and even wrote some articles on fractals for Acorn User.  Happy days, and so long ago.

30 years ago, in fact.  That's the reason for the post.  We all know about Moore's law, commonly quoted as "computer power doubles every 18 months" (although of course the reality is more complicated, but let's go with this for now).  One doubling of power doesn't sound much, but what happens after 30 years of Moore's law?

30 years is 20 doubling times. 2^20 ~ 10^6. (Impress you friends with fast mental conversions between powers of two and powers of ten by remembering 2^10 = 1024 ~ 10^3. Caveat: any friend who would be impressed by this feat probably already knows how to do it.)  So that would mean today's PCs are one million times more powerful than the humble Beeb.  Is this true?
  • Memory: 32kB RAM (yes, 32 kilobytes).  32 GB isn't common today (although it is on a reasonably high end scientific workstation): more like 4 or 8 Gigs typically, so, a quarter of a million times as much memory.
  • Processor (6502A) speed: 2 MHz.  More like a thousand times faster today, with a 3GHz processor (but, of course, that's with a 32 or 64 bit processor, not the Beeb's 8 bit one, and then there's multi-core, dual processors, and what not, giving another order of magnitude).
  • Screen: max resolution 640x256 (2 colours), or 160x256 (8 colours), using 20 kB of video RAM.  Today, my flat screen is 1920x1080 (4 billion, or 32 bit, colours), so that's about 8MB of video memory, or 400 times as much. 
  • Disc storage: a cassette player, or an optional 100 kB 5.25 inch floppy drive once you got fed up with waiting for programs "Loading...". Today, a 500 GB hard drive is more typical: that's 5 million times as much.
Okay, not every feature is a million times more, but combined, today's PCs are easily a million times more powerful than the Beeb.  And for less money!  The BBC Model B cost £399 (which is about £1200 in today's money), but that didn't include the monitor or floppy drive. The Torch dual 800 kB floppy drive cost around £800, although you got a Z80 co-processor thrown in for that.  In March 1987 I bought a 28MB (yes, megabyte) hard drive for £745 (or about £1600 in today's money).

To get a better feel for what this doubling means, think of a slightly older computer, Deep Thought, which took seven and a half million years to calculate the Answer to the Ultimate Question of Life, The Universe, and Everything.  That was in 1978, or 33 years ago, or 22 doubling times, or 4 million times.  If that was a speed improvement, today's equivalent of Deep Though would take only 2 years to calculate the answer!  Not so impressive now.

But wait, you say.  Douglas Adams was a genius.  He would have taken that into account.  The real Deep Thought would have kept upgrading itself, but even so still took 7.5 Myr to calculate the answer.  7.5 Myr is 5 million doubling times, or 10^1,500,00 more powerful.  That would make the Deep Thought who gave the answer 42 to the philosophers' descendents umimaginably more powerful than the original (if such a machine is even possible in the current universe).

Anyway, happy birthday, Beeb!

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