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MacOS 9 and Virtual Memory
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Antbob
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Nov 19, 1999, 07:24 PM
 
MacOS 9 HAS cured my old problems experienced with 8.6 and my G3/450/UW. However, one thing that interests me is it's determination to turn ON Virtual memory. What's more - it seems to want 129MB of it !! What's up ? Isn't 128MB of RAM big enough for MacOS 9 ?
     
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Nov 20, 1999, 10:10 AM
 
I take it that you mean that even when you turn VM off it is turned on by MacOS?

Or did you just find it on after the install of MacOS 9? That is normal, VM is on by 'default'.

If you have 128M of physical RAM (which is what I think you implied) you do not really need VM and may turn it off.
     
Antbob
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Nov 20, 1999, 04:27 PM
 
Generally, if I turn it off the machine will crash out.
     
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Nov 24, 1999, 02:38 PM
 
Macintosh memory management is more efficient with virtual memory on than off. The only downside to VM is that code must sometimes be swapped to the hard drive.

The Mac technique of turning VM on, but leaving it set to just 1M more than physical RAM gives you the benefits of having it on, but seldom sends the Mac out to your hard drive.
     
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Nov 24, 1999, 04:37 PM
 
Actually, it is more stable with it off.
It ALWAYS swaps data to the hard drive as that is what VM is!
129MB is exactly 1MB over your physical RAM. That is the algorithm by default - RAM +1MB.
Apps use more memory with VM off, but that doesn't necessarily make it less efficient. Speed counts and VM slows things down.

Scott
     
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Nov 25, 1999, 05:55 PM
 
> Generally, if I turn it off the machine will crash out.

extension conflict? older stuff? old version of macsbug?

With major OS I firmly believe in reformatting first and doing clean install.

Start from Mac OS 9 All and see why. Rev 1's do seem to have more trouble.

Also, 9.0 on my BW w/ 256MB uses 60MB with VM off, 40MB with VM on. And, IE 4.5 is less prone to crash with VM off, which shouldn't be but seems to.
     
Antbob
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Nov 25, 1999, 07:18 PM
 
I reformatted as a formality. It's probably not necessary but I thought it best to start from a "clean slate". To be honest0 it seems to plod along ok with VM on and I'm happy if OS 9 is happy :-)
     
LukeGow
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Nov 25, 1999, 08:29 PM
 
chabig's reply of making your Powermac more efficient by turning virtual on is right on the money. In fact this was one of the certification questions in my Apple recertification exams for Apple Service Technicians. Luke.
     
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Nov 25, 1999, 11:13 PM
 
More efficient maybe, a better (and more stable) performer - no!
That is from the real world - not an Apple test!

Scott

BTW, that was not meant to demean you, but VM just plain bites. It does allow more apps per MB of RAM to run, but the cost is speed and reliability
     
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Nov 26, 1999, 04:17 AM
 
slboett, PowerMacs were ment to be run with VM on, thats why whenever you install a new os upgrade, if vm is off, the installer will turn it on. With VM, the macintosh does something called File Mapping, which loads the resource fork in memory, and leaves the data fork on disk. VM may slow down a typical G3 a percentage point or two, but in real world applications, your not gonna notice much of a difference. However, there are excpetions with this, like video/audio editing, where you have streaming audio/video data writing to disk. But these cases are few, and Apple has said that VM on is the way to go. Why would apple recommend do0ing something that makes your machine, "slower, and more buggy"?

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-See Yea!
     
Michael Orticari
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Nov 26, 1999, 10:56 AM
 
VM is the worst thing apple ever made. I have 160mb of ram in my imac. Once vm was automatically turned on, my system slowed down at least 20%. As I am a huge fan of mp3s; when playing mp3s with vm off in the SoundJam demo (for example) they NEVER have skipped a beat even when putting huge loads of work on the processor, however when I turn vm on the computer slows down considerably (i.e. switching applications takes longer) and playing mp3s doing almost ANYTHING results in them skipping regularly.

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Antbob
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Nov 26, 1999, 01:28 PM
 
VM was not "made" by Apple. VM has been around (in different forms) for ages. It CAN be useful in many areas and the best thing about it is that you can turn it off if it affects the work you are doing. It has some positive as well as negative effects... much like most things these days :-)
     
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Nov 26, 1999, 08:06 PM
 
Sorry Oscar, you may be the moderator here, but you comment on VM is just wrong. half of the apps I use choke and I mean choke with VM on - Photoshop, Virual PC, etc. My BW/400 w/256MB RAM and two 9GB Ultra2 drives is noticably slower and crash-prone with VM enabled. BTW, this is also the case for over 1 dozen other BW/400s and G4/400s I have. At home, my 7300/300 with 512MB of RAM slows way down if VM is on. I don't care what the default is or what an Apple test says, I have managed more Macs in 14 years than you can count, and I stand wholeheartedly by this POV.
As to why Apple would recommend doing something that makes my Mac "slower and more buggy" I have an easy answer for that one - PR. That's right. Apple could not and would not be able to sell a Mac with 32MB of RAM without VM as nobody could run anything but the darn OS!
Every (yes every!!!) Mac I have control over has real RAM and VM off. Each app may be more efficient in the technical sense as it uses less RAM, but it does is no way run as well/fast/stable.

Scott
     
Michael Orticari
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Nov 26, 1999, 11:24 PM
 
sorry about my error. I shouldn't have reacted so harshly. I do agree (now) that there are good and bad sides to vm. You just have to decide if it's right for you.
     
Antbob
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Nov 27, 1999, 06:34 AM
 
I share slboett's view on this. VM is ok is certain circumstances but as I said before - it does "sometimes" turn the Mac into a Tortoise (as opposed to a Hare!). I disagree on the point of it being a "PR/Marketing" ploy though - Apple knows that its users are a bit too clever to swallow that one.
     
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Nov 27, 1999, 02:08 PM
 
I really should have called it a marketing tactic (gimmick/ploy make it more sinister than it is).
It's true though. If you ran any 32MB Mac to day without VM, you couldn't do much (32 can't cut it anymore - but that is another topic). I can GUARANTEE anyone here this: If I secretly set half of my user's Macs to use VM - by the end of the day, ALL of them will have called me complaining about speed/freezes. Think about this. While we have 18-27GB of hard drive on each new Mac, if I used VM, it would also swallow from 513MB to 1025MB of hard disk space! That may not be too bad, but I also have user's with 512MB of RAM and just 4GB hard drives - that would use 1/8 of available hard disk space for VM!
Hey, if someone wants to use it and thinks it's better, by all means do so. But don't come here and say because Apple says it's better it is. I love Apple, the Mac and have since 1984 (I know, old fart) but everything they say isn't always the Gospel!

Scott

PS - if you spend as much time as I do on the Apple Tech Exchange, you'll actually see many expert users and Apple techs recommending turning off VM - depending on the issue...
     
Antbob
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Nov 27, 1999, 02:46 PM
 
If the hardware setup is not correct - I would recommend correcting it. It is very easy to look at Vm to solve a "low memory" problem but it is, most certainly, NOT the way to run things. Get your machines upgraded (simple answer) to get rid of any continuous memory shortages that you experience running everyday applications. With the hundred or so G3's under my command - I have opted to increase memory from day one. Also I make regular checks to ensure users leave Vm OFF because of possible application clashes.

BTW... The "I should know" attitude in your last replies is not a friendly way to show your point of view.
     
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Nov 27, 1999, 04:17 PM
 
"BTW... The "I should know" attitude in your last replies is not a friendly way to show your point of view."

Absolutely unintentional!

Scott
     
Aldie
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Nov 28, 1999, 02:58 PM
 
If you don't have very much RAM, turn it on.
If you have enough RAM and if its not really neccesary to runn all your favourtie apps, turn it OFF. System is more stable and faster with VM off.
     
fleshhorn
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Nov 28, 1999, 11:02 PM
 
Um no, the system is not faster with VM on, or more stable. In fact, quite the opposite. Some applications tend to crash occasionally or refuse to run at all with it off. Also, application relaunch time will not be cut down with VM off. Ask an Apple technician, I was trained as one. The only time you will notice VM slowdown is when you enter the actual Virtual Memory, IE that 129'th meg after the real 128 megs of RAM you have, which rarely happens. My work machine has a half a gig of ram, as do the other computers, we leave it on, as the Apple technicians suggested. This is generally the case with OS 8.1 and beyond. Wait until OS 10, you will love VM =)
     
Fox
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Nov 29, 1999, 09:58 AM
 
Hmm...I usually double my RAM with VM, mostly because I only have 128, but have around 8 or nine apps open all the time, it works, but after around 6 to 9 hours of work I can start to feel it working harder.

If, just in theory, I wanted to get the advantage of file mapping, and just set it 5meg over, is there a way to write it to the ram disk?

Although silly, I'm a dreamer so bare with me. OK!
     
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Dec 4, 1999, 10:17 PM
 
See this title: http://til.info.apple.com/techinfo.nsf/artnum/n15854

There are many more in there that go into depth on why you SHOULD use Virtual Memory. I like RAM Doubler, but it isn't yet compatible with OS 9.
     
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Dec 5, 1999, 05:04 PM
 
and conversely, ladies and gents, there are plenty of reasons to NOT use VM...

such as:

"Following up on the issue of DVD audio-video synchronization problems, a number of readers noted that disabling virtual memory and other programs can help greatly:

[Tim Rosencrans] "I'm an Apple rep for sears and demo days at compUSA and I have run into the same thing with both DVDs and quicktime movies Apple's official work around is to turn off virtual memory (note quicktime movies are only affected with the problem on OS 9.0).
PS. this has been a real problem with iBooks as the movies on the demo can get out of sync...unfortunately Apple's solution wont work for the iBooks as OS 9 will not allow virtual memory to be turned off as it requires at least 40M of memory."

[Jason Buck] "I have an iMac DV SE, and the only time that I have had ANY problems with the iMac DVD Player is when either I turn Virtual Memory on or I operate it while doing something notable in the backround. My recommendation is to try turning of VM and close all open applications before playing the DVD movie..."

the above was taken in whole from another venerable website, MacInTouch. There are many other instances where disabling VM has been of benefit. There are fewer instances where VM is actually required, unless you happen to have little physical RAM.


VM is neither all that GOOD when used all the time nor all that BAD when not used at all...

Running OS 8.6 on a 466MHz G3 beige minitower with 256M RAM, I never use VM and my Mac screams, I can't remember when it last crashed/froze/belched or otherwise behaved erratically in the slightest. A dream come true.
     
newsmac
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Dec 6, 1999, 09:26 AM
 
After reading the posts here, I decided to try turning VM off to see if it would make any difference. I recently did a clean install of os9 to solve some other problems on my G3/350. Although most programs do use more memeory (I have 128MB REAL) with VMoff, I have noticed a significant speed increase in opening apps, opening & closing windows, downloading files, image processing ect...so for now I'm going to leave it off. I had been using vm since july, but now im wondering if it was really necessary. i dont know about the efficiency part mentioned in some of the posts, but i havent had any freezes or crashes since turning it off, which is partly why i did the clean install, so for me, the stability issue seems to be solved.
     
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Dec 6, 1999, 03:07 PM
 
...And that is exactly what you should see. I don't care what Apple's tech notes say, or what some exam says, real-world experience on hundreds and hundreds of Macs over 14 years has shown the same results you are seeing.
People, think outside the lines a little - tech notes and exam questions are not the end-all of enlightenment. Listen to the users in the forums - that is where you'll find most of the right answers!

Scott
     
   
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