🚀 go-pugleaf

In article <970048@gore.com>, jacob@gore.com (Jacob Gore) writes:
> / gnu.misc.discuss / mjones@donald.aix.kingston.ibm.com (Mike Jones) /Aug 1'91/
> What does the width of the CPU external data bus have to do with the width
> of peripheral buses???
> 
> Maybe you can explain...  I heard this the first time when working at IBM
> eight years ago, and I still don't get it.

Well, if (for instance) your CPU data bus is 16 bits wide, then you have the
choice of either a) going with 16-bit peripherals, or b) multiplexing the
16-bit CPU bus onto an 8-bit I/O bus. In the first case, your hardware is
more expensive than the 8-bit equivalents (certainly true at the time the PC
was designed), in the second case you have additional parts, increasing the
cost.
  
> Or is the 3090 really an 8-bit machine, so it can work with EBCDIC
> terminals?

No, it has multiplexers; they're called 3725's and 3274's. In fact, 327x
terminals are serial devices; the 3274 attaches to a 32-bit CPU channel and
writes serial data down a coax line to the terminal.

     Mike Jones  |  AIX Development  |  mjones@donald.aix.kingston.ibm.com

The purpose of a programming system is to make a computer easy to use.
	- Frederick P. Brooks, Jr., The Mythical Man-Month