simon@ivem1.ucsd.edu (Simon) (06/25/91)
Hello. I have a Mac IIfx and 20 megs installed inside, 4x4meg SIMMS, and 4x1meg SIMMs. The problem is, the system only show 6 or so megs for use while the System seems to be taking the rest of the available ram (13megs). Does anybody know how to get the memory back into unused ram? Or is the SIMMs bad? Or are they in wrong? I don't think it's in wrong; the 4 meg SIMMs are in Bank B while the 1 meg SIMMs are in Bank A. Any help would be appreciated. -Simon -- * Simon Lee * Southwestern Regional Resource for * * simon@ivem1.ucsd.edu * Intermediate Voltage * * sulee@ucsd.edu * Electron Microscopy, UC San Diego *
xdab@ellis.uchicago.edu (David Baird) (06/27/91)
In article <5494@network.ucsd.edu> simon@ivem1.ucsd.edu (Simon) writes: >Hello. I have a Mac IIfx and 20 megs installed inside, 4x4meg SIMMS, >and 4x1meg SIMMs. The problem is, the system only show 6 or so megs for use >while the System seems to be taking the rest of the available ram (13megs). > >Does anybody know how to get the memory back into unused ram? Or is the >SIMMs bad? Or are they in wrong? I don't think it's in wrong; the 4 >meg SIMMs are in Bank B while the 1 meg SIMMs are in Bank A. > >Any help would be appreciated. >-Simon You did not say if you were running System 6.0.x or System 7.0. If you are running System 7.0 turn on 32-bit memory with the Memory cdev in the Control Panels. If you are running System 6.0.x or System 7.0 without 32-bit memory turned on, your machine can only access 8 megs of Ram. The System will keep all the memory because it doesn't know what to do with it otherwise. (OK, I know thats not a techie explanation, but it does "explain" the situation. :-) ). -- X-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-X X David Baird xdab@midway.uchicago.edu X X University of Chicago d-baird@uchicago.edu X X University Computing Organizations (312) 702-7161 X
brian@galileo.uucp (Brian Donnell [PT4]) (06/27/91)
In article <1991Jun26.170014.14999@midway.uchicago.edu> xdab@ellis.uchicago.edu (David Baird) writes: >In article <5494@network.ucsd.edu> simon@ivem1.ucsd.edu (Simon) writes: >>Hello. I have a Mac IIfx and 20 megs installed inside, 4x4meg SIMMS, >>and 4x1meg SIMMs. The problem is, the system only show 6 or so megs for use >>while the System seems to be taking the rest of the available ram (13megs). >> >>Does anybody know how to get the memory back into unused ram? Or is the >>SIMMs bad? Or are they in wrong? I don't think it's in wrong; the 4 >>meg SIMMs are in Bank B while the 1 meg SIMMs are in Bank A. >> >>Any help would be appreciated. >>-Simon > >You did not say if you were running System 6.0.x or System 7.0. If >you are running System 7.0 turn on 32-bit memory with the >Memory cdev in the Control Panels. > >If you are running System 6.0.x or System 7.0 without 32-bit memory >turned on, your machine can only access 8 megs of Ram. The System >will keep all the memory because it doesn't know what to do with >it otherwise. (OK, I know thats not a techie explanation, but >it does "explain" the situation. :-) ). > No - that is not quite right. System 6 and 24-bit System 7 can address 16 Megs of RAM. However, 2 Megs is reserved for ROM, and 1 Meg is reserved for each filled NuBus slot. It is important to put all your cards in the highest numbered slots possible to avoid fragmenting the address space. For example, if you have just one card (the video board) in the slot 6 of the Mac IIfx, then System 6 or 24-bit System 7 will be able to address up to 13 Megs for your applications (16 - 2 - 1). System 7 32-bit has similar limitations except that they start at the 1 Gig boundary instead of 16 Meg (I think - somebody correct me if I'm wrong on this one). In other words, the same machine above in 32-bit mode should be able to address 997 Megs (1Gig - 2 - 1). Why the System didn't put things at the top of the 32-bit address space (thus allowing 3997 Megs for applications) I don't now. Brian Donnell NASA/JSC
rmh@apple.com (Rick Holzgrafe) (06/28/91)
In article <5494@network.ucsd.edu> simon@ivem1.ucsd.edu (Simon) writes: > Hello. I have a Mac IIfx and 20 megs installed inside, 4x4meg SIMMS, > and 4x1meg SIMMs. The problem is, the system only show 6 or so megs for use > while the System seems to be taking the rest of the available ram (13megs). This has become a Frequently Asked Question. Here is the Frequently Provided Answer. :-) You are running in 24-bit mode. In this mode, the Mac's cpu only uses 24 bits for an address, which means it can address at most 16 Mb. But not all of that 16 Mb is used to access RAM; large amounts are used to access ROM, cards in the NuBus slots, and miscellaneous hardware. The upshot is that only 8 Mb are left for addressing RAM. Your System is using about 2 Mb of that, leaving 6 Mb available for apps. The remaining 12 Mb are shown as belonging to the System only because they are not in use by or available to apps; actually, they're unused. If you are running System 6.0.x, that's the end of the story. If you're running System 7, you have the following options, available from your Memory control panel. If you turn on Virtual Memory, and move all your NuBus cards into the slots farthest from the power supply, your system will make available an extra megabyte for each empty slot. For example, if your IIfx has only a single video card installed, leaving 5 empty slots, you could get back 5 Mb, making your total usable RAM 8 + 5 = 13 Mb. You can get back *all* of your RAM by turning on 32-bit addressing (with or without Virtual Memory; with 20 Mb, you probably don't need VM!). If you do this, your System will still use about 2 Mb, and there will be about 18 Mb free for use by applications. Warning: not all applications are "32-bit clean". Those that aren't will bomb in 32-bit mode. Use the Compatibility Checker stack that came with System 7 to check your disks for applications that may need upgrading. Hope this helps. ========================================================================== Rick Holzgrafe | {sun,voder,nsc,mtxinu,dual}!apple!rmh Software Engineer | AppleLink HOLZGRAFE1 rmh@apple.com Apple Computer, Inc. | "All opinions expressed are mine, and do 20525 Mariani Ave. MS: 3-PK | not necessarily represent those of my Cupertino, CA 95014 | employer, Apple Computer Inc."
brian@galileo.uucp (Brian Donnell [PT4]) (06/28/91)
>You are running in 24-bit mode. In this mode, the Mac's cpu only uses 24 >bits for an address, which means it can address at most 16 Mb. But not all >of that 16 Mb is used to access RAM; large amounts are used to access ROM, >cards in the NuBus slots, and miscellaneous hardware. The upshot is that >only 8 Mb are left for addressing RAM. Your System is using about 2 Mb of >that, leaving 6 Mb available for apps. The remaining 12 Mb are shown as >belonging to the System only because they are not in use by or available >to apps; actually, they're unused. > I don't think this is completely correct. As mentioned for System 7 virtual memory, System 6 and System 7 24-bit (w/o VM) can address more than 8 Mb (up to 13) depending on how many and which NuBus slots are empty. However, System 6 (I don't know about System 7) will still only allow a single application a maximum partition of 8 Mb - the system size. You can get around this by using just Finder in System 6. Also, older versions of Macsbug typically don't like address spaces larger than 8Mb. Brian Donnell
ph@ssd.kodak.com (Pete Hoch) (06/28/91)
In article <14270@goofy.Apple.COM> rmh@apple.com (Rick Holzgrafe) writes: >In article <5494@network.ucsd.edu> simon@ivem1.ucsd.edu (Simon) writes: >> Hello. I have a Mac IIfx and 20 megs installed inside, 4x4meg SIMMS, >> and 4x1meg SIMMs. The problem is, the system only show 6 or so megs for >> use while the System seems to be taking the rest of the available ram >> (13megs). > >This has become a Frequently Asked Question. Here is the Frequently >Provided Answer. :-) > >You are running in 24-bit mode. In this mode, the Mac's cpu only uses 24 >bits for an address, which means it can address at most 16 Mb. But not all >of that 16 Mb is used to access RAM; large amounts are used to access ROM, >cards in the NuBus slots, and miscellaneous hardware. The upshot is that >only 8 Mb are left for addressing RAM. Your System is using about 2 Mb of >that, leaving 6 Mb available for apps. The remaining 12 Mb are shown as >belonging to the System only because they are not in use by or available >to apps; actually, they're unused. > >If you are running System 6.0.x, that's the end of the story. If you're >running System 7, you have the following options, available from your >Memory control panel. > >If you turn on Virtual Memory, and move all your NuBus cards into the ^^^^^^^^^^^^^^^^^^^^^^ >slots farthest from the power supply, your system will make available an >extra megabyte for each empty slot. For example, if your IIfx has only a >single video card installed, leaving 5 empty slots, you could get back 5 >Mb, making your total usable RAM 8 + 5 = 13 Mb. WRONG!!! WRONG!!! WRONG!!! The original poster has 20MEG of real RAM. Since the largest memory partition you can have in 24-bit mode it 14MEG, YOU CAN NOT TURN VM ON!!! Beleve me I have tried. I even set my machine to 32-bit mode, turned VM on, and set my partition to 21MEG. (I had to use 21 MEG because VM disables itself if you try a partition <= real RAM size) Then I switched back to 24-bit mode but poof VM was off again. The only solution is to reduce your real RAM size to something less then the VM partition you want to set up. Then you can use VM again. In my opinon this really sucks. So would everyone stop spreading this myth that you can have a 14 MEG of memory in 24-bit mode on the Mac. You can do it ONLY if you have less than 14 MEG of real RAM! By the way I would love to run in 32-bit mode but I have software that I use every day that breaks in 32-bit mode. And yes I am looking for a replacement for this software. Pete -- Pete Hoch | ..somewhere..!kodak!ssd!bashow!ph ..or.. Color Systems ISPD. 3/65/RL | ph@ekcolorlink.ssd.kodak.com ..or.. Eastman Kodak Co. | ph@bashow.ssd.kodak.com Rochester, NY 14650-1805 | 716-722-3285
minsky@media-lab.media.mit.edu (Marvin Minsky) (06/28/91)
I can't get my IIfx to recognize more than 7Mb with system 7, even when there is only 1 nubus card, the display card, in the right hand (number 6) slot. (All 20 MB appear in 32-bit mode.) Any other ideas? Does it matter if the 4MB Simms are first or last?