General question about ISA bus and memory layout

[Chuck(G)]

In the PC system of things, there is a card guide in back for full-length cards; anything shorter than that depends pretty much on the one screw and edge connector for support. Don't get me started on the lack of any sort of card extraction system to avoid chewing your fingers up on stubborn cards.

Had IBM adopted the NEC C-bus system (shared by many other buses) of a card that slides into a slot, things might have been different. Better airflow, no chewed-up fingers--and a bus that starts off as 16-bit.

There are other things to like about NEC 9801-family software, even with its superior graphics. Support for 4 floppy drives, right out of the box. The partitioning scheme for the hard disk allows for 16 single-level partitions--you can boot from any one of them. The BIOS started off by allowing booting from any floppy, hard disk, or MO drive...

And the one I like the best--the floppy format is exactly the same from 8" through 5.25" down to 3.5".

 

[geoffm3]

Well, IBM did take a stab at making a better PC bus, which is what MCA was supposed to be. Seems like most of the complaints about MCA have more to do with its restrictive licensing and royalty requirements rather than the technical aspects of it. From an interconnect standpoint it was certainly better than VLB (very long bus) and EISA (I can't imagine that card edge or connector being cheap from a manufacturing standpoint).

 

[sergey]

As Chuck mentioned IBM PC was intended to be a cheap experiment. That pretty much explains why it uses 8-bit data bus, and why ISA is nothing more than buffered CPU busses.
We must admit that it worked pretty well. I don't think any other systems had more cards built for them.