[aprssig] Dual Serial Port PCMCIA card; $50

[Mike Yetsko]

> The print in the ad says this.  I am not picking on
> you, and the picture is of a PCMCIA card, isn't it?
> 
> In bold print in the ad it says PCMCIA.

Yes, but it is VERY misleading.  PCMCIA is the original 16-bit hot-
swapable 'port expanded' card interface.  When it was enhanced, it
became PC-CARD or CardBus, although it's sometimes refered to 
as 32-bit PCMCIA but that is not a recognized designation.

PC-CARD and PCMCIA look ALMOST identical.  (There's also
a variant that is 3.3v only, with a slot key, but we won't go there 
for this...)  USUALLY, but not always, you can spot PC-CARD
by the metal shield fingers on the connector.  Other than that, most
people couldn't spot the difference.

MOST PC-CARD devices will work ONLY in PC-CARD slots.
There are a few that will work in PCMCIA, but they are not very
common.  Or maybe I just haven't been exposed to them.  (And I
have probably 100 or more cards of various types here, and have
had access to maybe 500 to a 1000 at one time or another.) 

PC-CARD is PC-CARD.  PCMCIA is PCMCIA.  But they DO
share the same physical connector and form factor.  (As I said, 
PC-CARD is a 'hot swapable' PCI device.  This is NOT the 
same thing as 'compact PCI'.  That is essentially PCI cards on
a special connector.  They are NOT 'hot swapable', and you 
will more than likely do bad things of a permanant nature if you
try to insert or remove compact PCI cards with the power on.

If you have a PCI bus enumerator, and you have PC CARDS inserted
and active in your machine, the PCI bus walker will see the 
PC-CARD device just like any other device that appears on the 
PCI bus.  The ONLY thing that distinguishes these devices from
internal 'on the bus' devices is the fact that they would be identified
as on the branch of the tree 'through' the CardBus controller as on
a sub-bus.

MOST, but not ALL, PC-CARD slots will also accept the older
PCMCIA cards.

PC-CARD (or CardBus)  is a 32-bit PCI style interface on the 
PCMCIA 'pin' connector.  CardBus controllers are a PCI bridge
device, just like you have in your desktop for PCI bus interfacing
except that they are slightly enhanced to have power sensing and
triggering.  As such, they are PCI INTERFACE SPECS!  They 
are NOT PCMCIA spec.  

I cannot stress this enough.  PCI is TOTALLY DIFFERENT 
FROM PCMCIA.  They are not the same thing AT ALL.   

PCMCIA is effectively a PC-AT bus expansion with ONE 
IRQ line.  PC-CARD is a PCI bus extension through a CardBus
controller as a bridge with NO PC interrupts, just PCI-IRQ bus
interrupts.  

As I said, if you're somewhat knowledgable about PCMCIA and 
CardBus, there was no question about what the ad said, and 
what it didn't say. 

But it does look like someone who really didn't know what they
were talking about when it comes to the hardware did the final
copy of the ad.