Dumb processor question and memory question

allano,

Here are some reference sites:

RAM

http://en.wikipedia.org/wiki/Randomaccessmemory

Click on some of the other topics like Related_terminology.

On a Mac, if you click once on an icon for a program and select "get info" from "File" in the menu bar, you will see a place to allocate memory. Think of the chips as tables and chairs in a restaurant. If you are going to have a wedding dinner, you will need to reserve more seats than if you are just meeting two friends for lunch. Each RAM stick is a table and each chip is a chair. You may not need all the chairs but you can still reserve the whole table if you like.

On older machines, if you open three programs in order, A, B and C, and then close A, the RAM reserved for A is not available for program D until you close B and C too. In other words, just because you close a program does not mean that the RAM is instantly available for something new. There are a lot of tricks to making good use of RAM so take the time to learn more.

Virtual Memory was 'invented' in the days when RAM chips were very expensive. VM is just a way of tricking the CPU into using some hard drive space as fake RAM storage space. It is not as fast because the computer has to wait for the drive to spin into position to get the information being sought.

Hope this gets you started. Enjoy. Also, do not be afraid to ask all the questions you want. We do this for fun too.

Ji˜m

BTW, are you in Portland?

1. Choose Apple System Profiler from the Apple menu and look for the processor speed.

2. Open the Memory control panel in the Control Panels folder in the Apple menu to check and change the current virtual memory configuration.

3. Defragmenting is something which can be done to hard disks and similar storage mediums. When done, it places all of a file's components next to each other on the drive's storage for faster access. It is not something which can be done with RAM.

(20111)

How do I find out the speed of my processor?

Go to the apple menu (apple icon in upper left) and open 'apple system profiler'. It will tell you not only your processor but how much ram you have and in what amounts. If you want to find out more details about a certain item click the triangles so they face down.

I've got an iMac from around 1999. I think it's the first one. It has a pull out CD-ROM drive.

The iMac first appeared in the summer of 1998. It appears you have the tray cd rom model from the first half of 1999 before the DV models came out in september 1999.

Where can I learn about memory and reallocating it.

If you are refering to system memory go to 'apple menu' - 'control panels' - 'memory'. There you can turn on/off virtual memory and allocate hard drive space towards ram usage if you are short on ram. Note this will slow the system down.

If you are talking about application memory go to where the applications are found, probably in the applications folder. Then click info (apple I) and go to memory and increase the ram usage to the disired amount.

Also what defragmenting (is that what it's called?) is.

Don't worry about defragmenting on your system unless your hard drive is full. The format of the hard drive is called HFS+ and almost eliminates the need to defrag. To find out how much space a hard drive has and has available click once on the hdd icon and click get info.

iMac DV 400 Mac OS 9.2.x

Thanks so much. One question, though. I'm looking at About This Computer. I see "Built-in Memory", "Virtual Memory", "Largest Unused Block and that MacOS takes up 28.9 MB (is that RAM?).

Yes.

I don't see anything about the processor.

To see the processor speed, choose Apple System Profiler from the Apple menu if that menu item is present, and look through the information provided by it.

(20122)

allano,

How much built-in memory do you have?

What system are you using?

OS 8.5 takes about 18 megs of RAM.

OS 9.2 takes about 23 megs of RAM.

You can disable several extensions and reduce the system RAM requirements.

Jim

Jim-

Virtual Memory was 'invented' in the days when RAM chips were very expensive.

I hate to point this out because it dates me so badly. Virtual memory was actually invented before the existence of dynamic RAM chips. It was invented by some researchers because CORE memory was so expensive.

Core memory was made from small (not quite microscopic) magnetic donut-shaped ferrite cores that were strung on wires. Typically, each core had an X-wire, a Y-wire, and there was one sense wire that ran through the entire X,Y array (referred to as a core plane) which held the data for one bit. Not only was it expensive, but it was also physically large and power hungry, and made the "mainframes" of the mid 1960's take up an average sized living room for the compute power and storage equivalent of the original Macintosh.

Grant,

Thanx for the clarification. I should have said "virtual memory on a Mac was introduced because RAM chips of the day were very expensive."

It is always good to keep things in historical perspective. Otherwise, we might also forget to thank all those guys at Xerox PARC. Do you know of a good picture on the web for the X Y array? That would be a fun project to replicate.

BTW, it is the color of my hair that dates me. Losing my youthful figure does not help any, either.

Jim

allano,

Grant's comment prompted me to go back to Wikipedia and look for some pictures of some of the earliest hardware.

http://en.wikipedia.org/wiki/Virtual_memory#History

"Virtual memory was introduced to the x86 architecture with the protected mode of the Intel 80286 processor. At first it was done with segment swapping, which becomes inefficent as segments get larger. With the Intel 80386 comes support for paging, which lay under segmentation. The page fault exception could be chained with other exceptions without causing a double fault.
[edit]Windows example
Virtual memory has been a feature of Microsoft Windows since Windows 3.0 in 1990; it was done in an attempt to slash the system requirements for the operating system in response to the failures of Windows 1.0 and Windows 2.0. 386SPART.PAR or WIN386.SWP is a hidden file created by Windows 3.x for use as a virtual memory swap file. It is generally found in the root directory, but it may appear elsewhere (typically in the WINDOWS directory). Its size depends on how much swap space the system has set up under Control Panel - Enhanced under "Virtual Memory". If a user moves or deletes this file, Windows will blue screen the next time it is started with "The permanent swap file is corrupt" and will ask the user if he wants to delete the file (It asks this question whether or not the file exists).
Windows 95 uses a similar file and the controls for it are located under Control Panel - System - Performance tab - Virtual Memory. Windows automatically sets the page file to start at 1.5× the size of physical memory, and expand up to 3× physical memory if necessary. If a user runs memory intensive applications on a low physical memory system, it is preferable to manually set these sizes to a value higher than default.
In NT-based versions of Windows (such as Windows 2000 and Windows XP), the swap file is named pagefile.sys. The default location of the page file is in the root directory of the partition where Windows is installed. Windows can be configured to use free space on any available drives for page files."

The story behind Windows and their cheap imitation of the Mac OS is that in 1987, Apple announced release of the Mac II with 64 megabytes of RAM. IBM paniced and announced the IBM PS2 with OS2 even though they would not deliver those flops for 18 more months. Windows did not break the 640k, yes, 640k not megs, low mem limit until Windows 95, eight and one half years later. I was an avid Mac user and loved the thought of 16.7 million colors. To put it perspective, think of having $64,000 to go buy a car with a Mac and $640 to spend on a car using MS-DOS (remember, Windows was still a DOS program with all the underlying limitations of DOS. Radio Shack and Apple II computers of the day had 64k of memory. Bill figured 10 times that would be fine. Unfortunately for him, he locked that figure into DOS so tight that for the next decade, Microsoft had to play games like himem/lomem swaps to keep up with the Mac.

Some IBM compatible loyalists want to totally ignore history and the early power AND convenience of the Mac. Limitations of the Mac were mostly political/OS biased and not hardware limitations. Maybe that is why my Quadra 700 still makes me more money than any other computer. Because it still gets the job done.

Jim

PS, Historical corrections welcomed. : )

It is also important (from an architectural standpoint) to notice that virtual memory requires a "hardware assist" to run fast enough to be useful. It needs a hardware "scoreboard" to tell which blocks of memory have been modified.

At the same time, adding a virtual-to-physical hardware address translator means any real address can be used as any virtual address -- dramatically reducing moving blocks of data around just to get them at the right address.

If I am remembering correctly, these two hardware assists were present as add-on chips (called Memory Management Unit, MMU) for the 68020, and were pulled into the processor chip for the 68030.

Hi

Read this post as there was plenty of fascinating historical information of interest, much of which I can remember. A couple of points for you which were touched upon but not really expanded upon.

Disk Fragmentation can cause performance loss if you are having to use it to make up for a shortfall of actual RAM. Its always a good idea to run defragmentation utilities (Norton Utilities Speed Disk was a good one) to reorder the drive (as has been stated) making available to Virtual Memory larger amounts of drive space in one contiguous block.

Its also a good idea to increase the size of the hard drive and its speed (if possible) as these too can improve VM performance – if RAM is limited. The iMac G3 333Mhz (probably rev, C or D) tray loader was capable of having 384MB of RAM installed (512MB if you upgrade to OSX).

That is an interesting Wikipedia article. But what is most interesting is that it seems to completely ignore the history of anything before Personal Computers. Personal Computers did not spring, full grown, from their father's head. They were deployed into a land where room-sized Mainframes were king, and MiniComputers were like small rodents busily stealing their lunch.

Mainframe computers, where virtual memory was invented, minicomputers like the PDP-11, and its offspring the VAX, all used Virtual memory before the 68000 or 8086 were even available. It was never a question of whether microprocessor-based systems were going to use Virtual Memory, only a question of when.

Stupid architectural and business decisions forced Intel's computer architecture to perpetuate mistakes made in the 4004, and carry them up to and beyond the 8086 family. They wanted binary computer-instruction compatibility.

The 68000 was quite different from the 6800, and Motorola provided tools to help you migrate your code. It was a different processor. You were going to have to do some re-writing, but they made it not such a big deal. The Motorola processor was better. But it was later, and Intel was there first.

Hi allano

No I don’t think its silly, its a question of whether its financially viable or not. If you don’t have the cash to reinvest in applications you wish to use that work in OSX then there is no point in upgrading to OSX. In which case there is no point in upgrading to 512MB of RAM. As for buying a G4? A G4 processor is always going to be better than a G3 processor. There are some really good deals on eBay at the moment – its up to you I guess.

To be honest if you want to use OSX you would be better off investing your money in as new a mac as possible. The newer macs can accommodate more RAM and larger drives and also run the latest applications far more efficiently than your current iMac (or G4 for that matter).

However if all the functionality that you could possibly want from your current iMac is already there in terms of applications etc then upgrade to 256MB and leave it at that. Upgrade the OS to 9.2.1 or 9.2.2 if you can (available on eBay or specialist resellers – google them if you want or search this forum as there are plenty of links).

It seems to me that you are quite new to macs and computers in general, so my last bit of advice would be: Walk – don’t Run!

HTH

Hi, allano -

More about disk (file) fragmentation - Article #17933 - Disk Drive Fragmentation

More about memory (RAM) fragmentation - Article #19064 - Minimizing Memory Fragmentation