Interfacing Standards - Computer Busses - page 98

MOST HELPFUL BUSSES OF ALL-TIME

1. ISA bus . The ISA bus competed head-to-head with the MCA, and although it was

much slower, it triumphed, as it was compatible with the older PC bus. For many
years its performance was acceptable (16MB/s), but the advent of the graphical user
interface was the beginning of the end for it. It has sadly seen the number of PCI slots
increasing while it has seen its own connections reduce from over five, to less than
two.

2. RS-232 port . A classic bus, which is compatible (almost) with all the other RS-232

ports on every computer in the world. It provides a standard way to talk to devices,
such as instruments, other computers, and modems.

3. IDE bus . A rather quiet and unassuming internal bus, which does its job of interfac-

ing to disk drives well, without, these days, much troubles. It has reasonable perform-
ance (over 14MB/s) and does not really have any intentions of ever becoming any-
thing other than a disk interfacing bus. It, like Ethernet, has overcome early retire-
ment by increasing its transfer rate, but still keeping compatibility with previous sys-
tems. Its main competitor is SCSI, which is unlikely to ever to beat it for compatibility
and cost, thus it is likely to stay around for much longer than some of its earlier PC
partners. For systems which have less than four disk drives (in a combination of CD-
ROM or hard disks) it is still the best choice, and is often integrated in the PC moth-
erboard.

4. VL-Local bus . The bus that showed the way for local bus technology, especially the

PCI bus. It always knew that it was a short-term fix, but it did its job effectively and
quietly. Apart from the 80486, it was one of leading factors which increased the adop-
tion of Microsoft Windows (as it allowed the fast transfer to graphical data).

5. Parallel port . Another classic bus which was created to purely interface to an exter-

nal printer, but has now been developed to support a multi-attachment busses with
reasonable transfer rates (over 150kB/s).

Let's not forget about the great-grandfather of all the PC busses: the PC bus. It is now en-
joying a well-earned retirement (but can be pulled back from retirement at any time). It is the
bus that has launched a million computers.
Finally, the relegation zone for computer busses (in order of the problems that they have
caused or for their lack of adoption).

RELEGATION ZONE FOR BUSSES

1. ISA bus . Like the 8088 processor and DOS, it has a Dr Jekyll and Mr Hyde appear-

ance, and is both the top computer bus of all-time, and worst bus of all-time. It is the
bus, which, in the past, has provided the foundation for upgrading the PC, and has
gently handed over its mantel to the PCI bus. But, it has caused lots of problems as it
quickly fossilized the connection between the processor and the peripherals. Its major
problems were it fixed rate transfer rate, the way that it handled interrupts, its lack of
address lines (only up to 24), its lack of data lines (only up to 16), and the way that
fast, medium and slow devices all connected to the same bus (thus allowing slow de-
vices to 'hog' the bus). It started to show its age when 32-bit processors appeared
and as the motherboard speeds increased. The beginning of its end was the introduc-
tion of Microsoft Windows 3, which started to properly use a graphical user interface.
The VL-local bus quickly came in as a stand-in. From there on, local bus technology