x86 architecture concepts

The PIC does seem like a bit of mess

When the 8051 was introduced, it was damned elegent.

Everybody I knew loved it.

Since then, people have taken it and tried to use it in some very inappropriate (IMO) situations. For example, the architecture simply wasn't intended to deal with more than 64K of code, with external RAM, or with a stack-intensive language like C. Sure there are kludges you can use to do those sorts of things, but it's not pretty.

When used in the intended ways, the 8051 was (and is) rather elegent.

Even the most elegent hammer in the world doesn't make a very good screwdriver.

Never used either.

I've no complaints about RS-232. I've seen it misused and poorly implimented over the years, but I don't see anything wrong with the standard.

I wouldn't know, never used any of these.

What with Forth wrong is? Strange UPN you may find, but else?

And whats wrong with this?

Rob

It's hard to name anything that's right with it. Swinging several volts from a positive rail to a negative rail to transmit at a low symbol rate for a few meters...

The 'standard' involved a DB-25 connector with about a dozen signals, which everyone implemented differently...

How many manhours has been wasted dicking around with serial cables?

...

Having seen the standard being used to transmit down a couple of kilometres, obviously I am wrong.

Unless of course you are referring to the MIS-interpreted

RS232 did NOT specify the conncetor until RS232-C onwards. The DB-25 connector was a PTT standard (CCITT later ITU-T) specification for modems, hence the DTE/DCE specifications. Also the synchronous/asynchronous for 300baud to leased line specifications.

RS232 did not specify things like DTR/DSR or CD/RI that was the modem specifications hence NULL modem cables.

Mainly by those who did not understand the standard and grabbed any old cable.

It's been a long time since I last designed with and programmed a PIC (in Assembly) but I will comment on it all the same. AFAIK the PIC was derived from an IBM peripheral controller (IIRC PIC stands for peripheral intelligent controller) and it was meant to provide an additinal (yet minimal) level of intelligence, flexibility and compactness where usually plain logic would do fine. I think the problem with PICs is Microchip simply extended it far beyond the original architecture could stand and so they ended with a jurry rigged solution. Just as with 8x51. For that matter the x86 architecture suffers the same problem in order to support legacy applications.

Just my EU0.02.

I think it was actually Peripheral Interface Controller.

I don't think it was IBM, but the rest is mostly right. General Instrucments adapted the PIC from a Signetics design back in the 70's to handle I/O related tasks for some other long since extinct processor. I think originally it came from Harvard or somewhere.

Well put. The PIC, the 8051, and the IA32 have all suffered from the universal hammer syndrome.

While the RS-232 "standard" may be adequate for the initial purpose of connecting a serial signal from a computer (DTE) to a modem (DCE) in an adjacent rack, the worst problems with RS-232 for any general purpose interface is the far too high impedance levels compared to any realistic cable characteristic impedance and the problem with ground potential differences, since no galvanic isolation is required.

Paul

I have the original introduction by Morse the designer of the

The real mess didn't start until the addition of protected mode. Even so, some Unix clones (notably Coherent) show that there was a way out.

But Microsoft killed the attempts of IBM to get out of the BIOS morass (microchannel) and forced Intel to introduce the "virtual real mode".

Even so Linux proves that if you ignore sufficient of its features the Intel 386 is a decent processor. A great deal of the mess in a Linux system has to do with the battle for the control of the boot code waged by Microsoft (BIOS).

IIRC, Intel's part was called the Programmable Interrupt Controller. It was basically a dedicated function 8 bit controller. My 8085 books are all in storage or I would look it up.

Bob McConnell N2SPP

I've just recently finished a project very like this - translating from COP8 to NEC 78K0 using a pure algorithmic translation method. It worked amazingly well; I was very surprised.

What do you think the standard says?