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Ask Dave
by Dave Hamilton

He from whom all Mac knowledge flows...




The Truth About Virtual Memory, Purging RAM, and the Desktop
March 25th, 1999

Ah, has it been another week already? Well, ready or not, here I come with another brand new batch of questions and answers. These were tough this week, folks... you're making me work here! But enough of my yackin' -- on to the questions:

 

Mark wrote: "I was told by Apple to keep virtual memory on regardless in my Wallstreet G-3 266. I will be upgrading RAM from 64 to at least 96, possibly 128. Does that mean I should turn virtual memory off, to avoid errors, or does the 'virtue' of virtual memory still hold for the PowerBooks? Some observers think that in 8.51 and succeeding systems, it will be a plus to keep the virtual memory switched on."

Hey Mark --

I'm not sure why Apple is so hot about having virtual memory on in the first place. Their implementation of it is mediocre at best, it slows the system down immensely, and with certain programs (browsers especially) it causes unnecessary crashes and freezes. Whew! Sorry 'bout that, I guess it had to get out!

Anyway, when it comes to a PowerBook, there's one more reason to disable VM: battery life. Virtual Memory, by nature, accesses the hard drive instead of RAM in many instances -- that's what it does. If you're using your PowerBook with batteries, you want your hard disk to be able to spin down and stay down for as long as possible (to prolong battery life). The more the hard disk spins, the more juice it uses and the quicker your batteries die. If you've got Virtual Memory on, there's a much greater need for the hard disk to be accessed, and therefore a much greater chance for the system to power up the drive.

My recommendation (on ALL Macintosh systems) is to disable Virtual Memory unless you absolutely need it due to lack of physical RAM.

:)

Jim wrote: "Ever since upgrading to 8.5, if I double-click on a SimpleText text document, the computer waits for about 5-10 seconds and then reports a -2048 error and says that SimpleText cannot be found.

If I launch SimpleText, and open the document from the File-Open menu, it'll open, but many times it's just a read-me file, or a quick note that I dashed off to myself that I'd like to open simply by double clicking. Neither will a SimpleText document open if I drop it on SimpleText, or an alias thereof.

This problem persists with System 8.5.1. I have tried reinstalling SimpleText, but the annoyance persists. A "get-info" shows the version of SimpleText on my machine to be version 1.4, and it references that it came from MacOS 8.5.

I do not experience this problem with SimpleText Read-only files, only with the text files.

Norton Utilities doesn't fix the problem, or any other shot-in-the-dark like rebuilding the desktop"

Hey, Jim --

Until I read the bottom of your message, I was certain that it was a desktop problem. And, I still am. One of two things could be happening here that's causing your problem. It's possible that you have more than one copy of SimpleText on the system, and when you rebuild the desktop it's registering the wrong one (perhaps a damaged one) as the handler for "TEXT" files. Do a "Find" for SimpleText. List the results by size. With OS 8.5 (or 8.5.1) the SimpleText you want to use is approximately 120k. Click on it and do a "Get Info" from the "File" menu to make sure that it's version 1.4. Then open it up and make sure it works. Once you've confirmed that this copy of SimpleText is good, go and delete ALL the others.

It's also possible that you have a damaged desktop database which isn't fixed by doing a "normal" desktop rebuild.

I recommend using TechTool to rebuild your desktop. TechTool's Manufacturer, Micromat, has this to say about desktop rebuilds:

"A standard rebuild simply updates the existing desktop database. If the file structure is damaged, that damage will still exist upon completion of the rebuild, causing future problems. TechTool doesn't rebuild the existing desktop, it deletes it and forces the Finder to create a new database."

Because of this, I recommend using TechTool to delete the desktop databases and start clean and fresh.

Try this, and let me know how it goes!

Ron writes, "Is there any info or products in the CDR with Firewire?"

Yes, sir! Sony recently released the Spressa i.Link drive, which is exactly that! We ran a story on it last week here as well. Good luck!

 

Cornelius writes: "I am using OS 8.1 on a PM8500 upgraded with Newer Maxpower Pro PPC 750 250mhz (512k cache running at 166.86) and 112 mb ram. I am always opening and closing different applications which I suspect fragments my memory. If I do not restart every so often I end up eventually crashing. Most of the apps. I use are memory intensive. Is there a way to de-frag or restore memory that would be easier than restarting the computer all the time? I have heard that OS 8.5 is better about releasing memory but I have held off upgrading because of several incompatibilities with the many apps. I use plus it is officially not recommended by Apple for this computer. Maybe it is time to consider upgrading anyway?"

Well, there is one utility that I've used with limited success called Mac OS Purge. It will release any temporary memory that is not "locked" or fragmented. Sometimes this can help, especially if some resource gets loaded "between" two programs that have since been "Quit." That resource in the "middle" can fragment memory and keep you from seeing the two chunks as one. The problem is that, many times, once resources are loaded, they are marked as "locked" and nothing short of a Restart will free them. It's unfortunate, but it's a fact of life with the MacOS.

And, again from Cornelius: "My other question: I get the blinking question mark when starting or restarting occasionally. Not very often but once in a while. Restarting from the keyboard usually restarts successfully. I know that this usually means that it could not find a volume with a valid system file. I had heard about this problem on other select Macs but not the 8500. I never noticed this before upgrading to the Maxpower Pro. Maybe it has something to do with it?"

Maybe. It's possible that the documentation from Newer instructed you to clear your PRAM or "CUDA" chip when you installed the upgrade card. One of the things that's stored in PRAM is your Startup volume. Go to your "Startup Disk" control panel and make sure that the disk you wish to boot from is highlighted. That should help things along.

Whew! That's it for this week, folks. Should any problems arise in YOUR world, e-mail your questions to me and I'll put my nose to the grindstone for ya once again! :)

-Dave

is President and CEO of The Mac Observer, Inc. He has worked in the computer industry as a consultant, trainer, network engineer, webmaster, and a programmer for most of the last 10 years. During that time he has worked on the Mac, all the various Windows flavors, Be, a few brands of Unix, and it is rumored he once saw an OS/2 machine in action. Before that he ran some of the earliest Bulletin Board systems, but most of the charges have since been dropped, and not even the FBI requests that he check in more than twice a year.

Ask Dave is here to answer all the Mac questions you have. Networking, system conflicts, hardware, you ask it, he can answer it. He is the person from whom all Mac knowledge flows....


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