32-bit CardBus takes bandwdth to 33 Mhz if you're compatible
- By John McCormick
- Feb 05, 1996
The culprit is the desire for newer and more useful features, regardless of the
millions of PC Card devices already out there. CardBus, a new 32-bit PC Card interface
being adopted by the industry, has advantages over the 16-bit standard based on the ISA
bus--the most important being bandwidth doubling to 33 MHz.
CardBus also mandates a 3.3-volt power supply. Older 16-bit PC Cards run on either 3.3V
or 5V power, which is where the first incompatibility crops up.
Manufacturers of new, 3.3V notebooks aren't likely to volunteer to supply 5V power for
old PC Cards unless they're forced to do so by the CardBus standard. CardBus does call for
a voltage keying scheme to prevent mismatches, but as far as I know, it doesn't require a
CardBus to provide 3.3V and 5V power.
We can hope that a few hardware manufacturers will implement dual-voltage supplies for
a while, but there's a bigger compatibility problem looming.
Basic to linking software and hardware are IRQ/DMA (interrupt request/direct memory
access) signals. Unfortunately, these signals differ between the old 16-bit and the new
That means software drivers, the biggest source of incompatibility ever since we've had
16-bit hardware, will cause even worse headaches when there are two different hardware
standards to program for.
Now that Texas Instruments Inc. and Cirrus Logic Inc. are both making the PCI-CardBus
host controller silicon, look for rapid but uneven development of the new CardBus. For
more information, visit the Web site at http://www.pc-card.com.
I'll bring up the mobile and radio data-link issues in a future column.
I download a lot of e-mail and Internet text, which I look at in WordPerfect 4.1. Why?
It's small enough to run from a floppy and works with hundreds of macros I've created,
many of which don't work properly with later WP versions.
Here's an interesting problem that illustrates why I'm sour on some Windows
applications and software upgrades in general. While working in a new WordPerfect 6 for
Windows version, I popped in some downloaded text, or rather tried to. WP reported that
not only did I need a Standard Generalized Markup Language viewer, but also that one was
not installed. Curious, I tried another file and got "unknown file format."
I went through recent downloads, all using the same communications software from the
same source, and found that about half the time, WordPerfect 6.x couldn't recognize ASCII
format. I could import some files but not all by specifying that the original was in
ASCII. Some kind of line noise must have corrupted these files slightly.
Now if I were an average user with one word processor, my megabytes of downloaded files
would have been useless unless I knew to specify ASCII import. Even then, I'd have had to
import each file to determine its contents, because the viewer didn't work and there was
no way to tell it to look for ASCII.
Isn't software wonderful? Federal employment may shrink, but there'll always be a job
for the power user.
John McCormick, a free-lance writer and computer consultant, has been working with
computers since the early 1960s. He welcomes mail from readers. Write to him care of
Government Computer News, 8601 Georgia Ave., Suite 300, Silver Spring, Md. 20910.