Path: utzoo!utgpu!water!watmath!clyde!rutgers!rochester!cornell!batcomputer!pyramid!voder!apple!goldman From: goldman@apple.UUCP (Phil Goldman) Newsgroups: comp.sys.mac Subject: Re: Boot Blocks Message-ID: <6983@apple.UUCP> Date: 14 Dec 87 17:18:51 GMT References: <36343@sun.uucp> Reply-To: goldman@apple.UUCP (Phil Goldman) Organization: Apple Computer Inc., Cupertino, USA Lines: 34 In article <36343@sun.uucp> chuq@plaid.Sun.COM (Chuq Von Rospach) writes: >1) How can I find out what the System Heap numbers in the boot blocks are > set for? > >The reason I ask is that I believe most of the glitchies I've seen since >the upgrade to system 5.0 and multifinder are system heap exhaustion >problems. I read somewhere that the heap grew again (implying that the boot >block numbers got bigger) for Multifinder. But I can't find any program that >reads the blocks or writes the blocks or any documentation on what they >should be. > INIT 31 will guarantee that there is some minimum amount of memory free in the system heap (16k currently, I believe) before the startup application is launched and the system heap is resized dynamically under MultiFinder. Therefore, the number in the boot blocks has very little meaning; it only needs to be big enough to get the system up and going. There reason for the system heap "exhaustion" under MultiFinder occurs because there are certain cases when it is just not possible for MF to grow the sys heap "on the fly." The most obvious instance of this is when all of available memory is in use. However, it can also happen when the last application launched was forced to load into a relatively low memory address. Since the memory for this application cannot be moved, it provides a ceiling for the growth of the sys heap. Therefore, quitting other apps will not alleviate the problem (which shows up most frequently as the inability to open a DA but might cause a crash in extreme conditions), only quiting this particular app will. We are actively pursuing methods for making the memory for running applications more relocatable. -Phil Goldman Apple Computer