Path: utzoo!attcan!uunet!husc6!mailrus!iuvax!bsu-cs!cfchiesa From: cfchiesa@bsu-cs.UUCP (Christopher Chiesa) Newsgroups: comp.sys.atari.8bit Subject: Re: 800 memory management Summary: De-selecting Cartridge ROM on the fly, on the 800 Message-ID: <3735@bsu-cs.UUCP> Date: 24 Aug 88 06:15:51 GMT References: <2278@alliant.Alliant.COM> Organization: CS Dept, Ball St U, Muncie, Indiana Lines: 27 In article <2278@alliant.Alliant.COM>, lackey@Alliant.COM (Stan Lackey) writes: > It is my understanding that the old 800 has 8K of RAM which is somehow > switched out when a cartridge (esp. the BASIC cartridge) is installed. That is correct. > Is there any way to get temporary access to that RAM while the cartridge > is plugged in? From what I've been able to tell in the six years I've owned my 800, there's NO provision in the system design for accessing the RAM at "cartridge addresses" while the cartridge is present. Unlike the XL/XE, in which a controlling data register is accessible to the CPU, on the 800 this is electrically hard- wired: plugging the cartridge in physically de-selects RAM in favor of cart- ridge ROM. I would think that in order to do anything about this, you'd have to make hardware modifications to the 800 design, giving the CPU control over the RAM/ROM switchover process -- i.e., the very thing done by Atari when they created the XL/XE line based on the 800. If anyone has counter-proof of this information, I for one would be very in- terested to hear about it. Would indeed be a useful capability. By the way, just what CAN one do on the XL? I just got one to replace my 800, and would love to know what "new tricks" this ol' dog can learn! :-) -- UUCP: !{iuvax,pur-ee,uunet}!bsu-cs!cfchiesa cfchiesa@bsu-cs.UUCP