The 'A' series is a die shink version -- smaller silicon = cheaper to make.
 While the die is smaller, there is a narrower Vdd range.  The 'A' series
also has an MCLR filter.

                Vdd range       Process technology (microns)
PIC16C55        2.5-6.25        1.7
PIC16C55A       3.0-5.5         0.7

Hope this is what you are looking for.
Bill

At 05:58 AM 3/10/00 -0800, you wrote:
>I posted this yesterday but maybe it didn't show up.
>
>Besides the price, what is the difference between the
>16C55A-04/P and the 16C55-XT/P?
>
>Thanks.
>__________________________________________________
>Do You Yahoo!?
>Talk to your friends online with Yahoo! Messenger.
>http://im.yahoo.com
>