Memory Addresing

[FluffyMcDeath]

Xamiche wrote:
Hmm, I wonder why they are bothering to teach us about these microprocessors if the segmented memory addressing is so bad. If todays processors no longer use it, why teach it?

For the same reason we're all taught to type on QWERTY keyboards; not because it's the best, rather because there is a lot of it about.

QWERTY, for those who don't already know, was a layout designed specifically to solve the problem on mechanical typewriters, of people typing so fast that they would jam the keys. Dvorak, for example, is a much better layout and allows faster typing, but you are not likely to come across one of these. Why? Because QWERTY is everywhere. Why? because that's what people know. Why? Because that's what they are taught. Why? because QWERTY is everywhere.


Anyway, x86 based ISAs are massively common on the desktop, so you have to know them, even though the newer ones have contiguous memory addressing. Once you know how to do the segmented addressing, you'll be happy to throw it away and forget about it because you probably won't ever need it.

[FluffyMcDeath]

mjg59 wrote:

QWERTY was designed to allow typists to type faster without jamming the keyboard.

In that slowing the typist down so that the keys don't jam is faster than unjamming the keys all the time.

As a result, you can type faster on QWERTY without jamming it. People who claim that QWERTY reduces jamming by slowing you down are obviously either bad typists or have never used a mechanical typewriter - the first time I used one, I jammed it repeatedly.

Coincidentally, the first time I used a mechanical typewriter was while I was learning Dvorak.
[/quote]

And I jammed the keys on a QWERTY repeatedly. Novice typists will do that. But mechanical devices need time for the hammers to swing in and swing out again. Anything that delays the next keystroke helps avoid those collisions.

As to the Liebowitz article, the conclusions are more based on a desire to believe that the markets are rational and efficient than on whether Dvorak is better than QWERTY. Since they believe that the market knows best, they believe that QWERTY must be the same or better, and they bend the evidence to fit.

One rebuttal here

Comparing the two, I'm about 10 words per minute faster with Dvorak (85 compared to 75).

That's more than 10% faster, and thats not a small amount.

[FluffyMcDeath]

And anything that causes you to use hammers that are further apart (like, say, QWERTY) helps avoid those collisions.

Which is relevant for electric typewriters and computer keyboards how? It's no longer an issue so why haven't we switched?

The article is debunking the claim that the prevelance of QWERTY is a market failure. It's not. Dvorak is slightly better than QWERTY, but not massively so.

If the market works to bring the best to the fore, and Dvorak is better than QWERTY, then it hasn't worked. Dvorak IS better. The differences in opinion are about HOW MUCH better. Bif you believe that the market will always find the optimum solution, this is anathema.


Similarly, the 68000 beat the snot out of the 8086. IBM considered using it in the IBM PC (well, the engineers did, but they are geeky). However, IBM didn't want the PC to be too powerful as they didn't want it to compete with their BIG machines.

The IBM PC was a lowly crappy box that the asian manufactureres found easy to clone. IBM hated the cloners, but between IBM's in with the business world, and the cloners pouring out cheap knock offs so folks could work on their workfiles at home, the PC became the standard. At the time it was becoming the standard, there was far better technology available but the market doesn't favour the better mousetrap, it favours the one made by the biggest player, or the one that is easiest to copy, or both.