They always said that you learn something new every day. Thanks for the dual-ported tutorial. Rich ========================== Richard A. Cini, Jr. Congress Financial Corporation 1133 Avenue of the Americas 30th Floor New York, NY 10036 (212) 545-4402 (212) 840-6259 (facsimile) -----Original Message----- From: Eric Smith [mailto:eric@brouhaha.com] Sent: Tuesday, May 23, 2000 5:45 PM To: classiccmp(a)classiccmp.org Subject: Re: Altair parts substitutions that Specifically, a true dual-ported RAM chip has separate address busses and control signals/strobes (*RD and *WR, or *CS and R/*W, or the like) for each port. Dual-port RAM chips tend to be expensive and not very high-density, so they aren't commonly found in commodity computer hardware. It's usually more cost-effective to time-multiplex a single port. Current manufacturers of dual-port RAM chips include Cypress and IDT. There are even some quad-port RAM chips now.