Steve,

Okay, being self taught explains why you did not understand what I was saying in "Cherri put up or shut up".

But you should not blame your confusion on me, perhaps the way you think the hardware runs is not actually the way it does run.

Also I have some questions on things you have written in your on line book.

Are you willing to discuss this without rancor?

-- Cherri (sams@brigadoon.com), June 26, 2000

Answers

I understand a great deal about how computer hardware works, as a matter of fact. However, if there is some specialized vocabulary used only in the embedded systems world, I certainly might not understand it.

As for questions about my book, if they are legitimate questions that you actually want the answers to, I'm willing to discuss them without rancor.

-- Steve Heller (steve@steveheller.com), June 26, 2000.

Steve,

After reading your chapter on hardware, I have only one point. You implied that a 66 Mhz CPU could execute 66 MIPS. The fact is that each instruction takes a different number of cycles to execute.

From the "Intel 80386 Programmer's Reference Manual":

The DIV instruction takes between 14 and 25 cycles to complete.

While the MOV instruction takes only 2-4 cycles.

DIV is a more complex instruction than MOV, thus it takes longer to execute.

The 386, and later, processors changed the algorithm for the DIV instruction, and added an "early out" feature to the "subtract and shift" logic, which reduced the number of cycles needed to complete the operation. An original 8088 took between 86 and 172 cycles to execute the same DIV instruction!

Hovever, overall, I think you did a pretty good job of trying to explain hardware in a language that a newbie could understand.

<:)=

-- Sysman (y2kboard@yahoo.com), June 26, 2000.

Thank you for your comments. Actually, I did point that MIPS are not necessarily the same as MHz, in footnote 17 referenced in the section called "The CPU".

-- Steve Heller (steve@steveheller.com), June 26, 2000.

Little Red Riding Hood?

-- Virginia Wolfe (bad@moon.risin), June 27, 2000.