From: Dave Arnett Subject: Re: HP memory cards Date: 4 Oct 1996 18:09:36 GMT Organization: Hewlett-Packard, MCD The YORKE IC, which contains the Saturn CPU, has a single flat address space. This is a 512 kByte address space. I'll bypass the HP48SX legacy issues, which are significant, and point out that we wanted to be able to see half of the ROM plus the RAM when talking to cards, so we could still have a functional operating system. We therefore permitted the card to fill one quarter of the address space at a time. We published an article in the HP Journal in August 1995 where we discussed this overlapping address space methodology. If you can find a pointer to those articles (check the FAQ?), it will shed more light on the design issues. Good Day! Dave. ------ I don't speak for HP when I post here.