Raymond Ingles wrote: > On Mon, Mar 30, 2009 at 8:37 AM, Scott Holder <[email protected]> wrote: >> Note that on the off chance you're using something that requires 24 bit >> addressing, you'll have to switch it back and lose the extra RAM. > > Yeah, some older programs would 'hide' information in the upper bits > of the address, since the system didn't use those bits, and "Who would > ever have more than 8MB RAM anyway?" Those programs fail badly on > systems that *do* use those bits, of course. (Even Apple was slightly > guilty of this, since some of their ROM code wasn't "32-bit clean". > Fortunately, there's the "Mode32" system enabler to work around that.) > > As I recall, it was mostly some games that had that trouble... but > wasn't some version of Word or another guilty, too?
Not just some old programs, the Mac OS used the upper 8 bits for flags in the memory management. Apple always told programmers to NOT access these flags directly but to use system calls. When Apple changed to 32 bit addressing they changed the system calls so properly written code still worked. I forget if Word was 32 bit dirty or not but it was, so to speak, 20 bit dirty. M$ did there development work on a system that only handled 20 bit addressing "who needs more than 640K". When people started upgrading their 1Mb shipped Macs to 2 or 4Mb M$ programs wouldn't work. Apple jury rigged the OS to only load those programs into the first 1Mb of memory. -- Clark Martin Redwood City, CA, USA Macintosh / Internet Consulting "I'm a designated driver on the Information Super Highway" --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Vintage Macs group. The list FAQ is at http://lowendmac.com/lists/vintagemacs.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/vintage-macs?hl=en Low End Mac RSS feed at feed://lowendmac.com/feed.xml -~----------~----~----~----~------~----~------~--~---
