BS: Virtual or physical memory

Subject: BS: Virtual or physical memory
From: Jeep man
Date: 08 Nov 04 - 04:15 AM

What is Virtual memory and physical memory RE my computer? Jim

Subject: RE: BS: Virtual or physical memory
From: s&r
Date: 08 Nov 04 - 08:03 AM

Physical memory is in the form of memory chips called RAM. It's fast to access. Virtual memory is part of the hard drive used by the operating systemm as though it is memory - it's slower. Generally the more RAM the better because there is less writing/reading to the hard drive.

Stu

Subject: RE: BS: Virtual or physical memory
From: The Fooles Troupe
Date: 08 Nov 04 - 08:12 AM

Virtual memory is pretend memory - implemented by software by swapping stuff out to the Hard Disk - physical memory is the RAM.

The physical bits you can kick - the virtual bits you can only swear at!

Subject: RE: BS: Virtual or physical memory
From: mack/misophist
Date: 08 Nov 04 - 10:42 AM

It's called 'virtual' because it mimics RAM when there isn't enough of it for the needs of the moment. It's much slower. Get as much RAM as your OS is able to use. (Up to a point, that is. A home machine probably can't use a gig of RAM. I have 768 megs of RAM but I cheat.)

Subject: RE: BS: Virtual or physical memory
From: JohnInKansas
Date: 08 Nov 04 - 05:42 PM

I'd disagree about the home machine not profitably using a "gig of RAM." Assuming WinXP and expected "improvements," 1,024 MB (1 GB) is about the minimum for any new machine I'd consider, and is what I use now on my main machine. Wish I had about twice that - sometimes. Many users won't benefit a lot from having more than 512MB RAM with XP, and some might get by with the 256MB that's fairly common, especially with the "Home" versions of XP and office programs; but failure to provide enough RAM is one of the most common causes of "doggy" performance.

I'd also be careful about the "as much RAM as the OS is able to use," since WinXP can use ENORMOUS amounts of RAM. The WinXP OS is capable, I believe recalling, of using 32TB of RAM if it's available, although you'll likely run into BIOS (and other) limits before you get there with currently available stuff. (One limit is that the Windows Explorer version in WinXP sometimes loses things if an individual copy/paste exceeds some value (32GB? or maybe it was 32TB?), since the program can only keep track of a limited number of memory addys when it lists the clusters to copy.)

For Win95 and Win98 (and for some of the obsolete NT versions) there were "maximum recommended" amounts of memory. The OS has to keep track of where stuff is and in Win98 the "tracking" could only be done in RAM. The RAM used for the "keeping track" part could get bigger than the "usable part" of the system RAM. They called it "memory thrashing" - although that term is/was also used for other behaviours in different contexts.

When Win98 was new, people noted that more than about 256MB of RAM would actually slow the machine down - depending on what applications you were running. A GB of RAM on a Win98 installation could make it just sit there and mumble to itself, without getting much productive work done. Current Win98 setups often do use more RAM than was recommended earlier, so apparently some memory handling improvements have been added incrementally, possibly by permitting some of the "bookkeeping" to be done in VM.

There have been no reports of "too much RAM" with WinXP, at least that I've seen; although it is possible to install more than is really useful.

Even with unlimited RAM, certain things are still "paged" in and out of Virtual Memory, so it's also important to have enough free space in the System Partition to provide adequate VM. Since WinXP will not use more than 10% of the free space on the system drive, by design, an adquate HD size for good performance may seem incredibly large to those used to older OS machines.

John

Subject: RE: BS: Virtual or physical memory
From: Jeep man
Date: 08 Nov 04 - 11:01 PM

Thanks, folks. Jim

Subject: RE: BS: Virtual or physical memory
From: mack/misophist
Date: 09 Nov 04 - 11:06 AM

Thank you, John is Kansas. Since the only windows machine I see regularly is 98se, I tend to forget about xp. While we're at it, what's your opinion of rambus?

Subject: RE: BS: Virtual or physical memory
From: skipy
Date: 09 Nov 04 - 03:58 PM

Just because you have memories of butterflies in your youth it does not mean that you are not a replicant!

Subject: RE: BS: Virtual or physical memory
From: JohnInKansas
Date: 09 Nov 04 - 04:32 PM

mack -

I'm not looking for a new machine at present, so I don't really need an opinion on RAMBUS. It's one of several proprietary types of memory for which higher transfer speeds are claimed. While it claims to be 6x as fast as SDRAM, it's also 6x as expensive - at least at end-use prices.

A danger with proprietary stuff like RAMBUS is that it may go away just before your chip fails and you won't be able to get a replacement - or some other similar little thing. (Think BetaMax?.) RAMBUS does have some Intel backing, so probably is viable for the near term.

A few builders offer machines with RAMBUS installed. Dell and Compaq I believe both have offerings. If they're willing to back it, I wouldn't worry too much about the obsolescence factor **; but there are quite a few other features I'd look for before RAMBUS vs. SDRAM would be significant. Machine performance tests have shown marginal improvement from using a particular type of "fast" RAM, RAMBUS included, since other bottlenecks limit the benefit you can get that way.

** Major maker backing doesn't mean freedom from obsolescence. Many laptops have used "special form factor" RAM that is NOT AVAILABLE if you decide you need more memory a year or two later. (I have one of those laptops.)

Those looking for minimally priced machines will see "XXXMB shared RAM." This is somewhat of a "red flag" since it means (usually) that the machine has a video driver and/or sound module built into the mother board that "shares" the machine RAM. Since it takes at least 16MB for a minimal display at display resolutions commonly used, and 32MB typically for "full color," and the sound module may reserve similar space, you only have "what's left over" for running your programs. Frequently, in machines in this class, even adding more RAM is not too helpful because of other bottlenecks. This might be okay for "granny" to use to send you email from the care home - but only if the care home doesn't have much of a "social program" so that granny has nothing else to do. Your kids (and computer-phobic spouse?) will likely want to play games that will tax this kind of machine severely. These machines have their place, but most users will find them "limiting" if they're the only one available. Think "2d machine" maybe.

At the basic office/homeoffice level, most(?) machines will have a separate video card with its own RAM built in. Cards with 32MB are considered "minimalist" now, and gamers frequently use 256MB "dedicated memory" cards. Quite a few basic office machines still offer "*** built-in sound" that may not stress your RAM; but a separate sound card is also a big help, particularly if you plan on MP3, MIDI, or any other sound work. Sound cards probably still start at 16MB dedicated (on the card) RAM, but are availabe with up to 256MB or above, I believe. (? I haven't checked recently on what's available.)

*** Although the "built in sound" will likely have the name of a reputable sound card maker, the card maker will refer you to the OEM computer mfr for support. The computer maker won't know anything about the card - they just buy it and plug it in. A separate card is necessary if you expect to want help/support. (Most people likely to want significant support will have other reasons for the separate sound card.)

Even with unlimited RAM, certain functions are still paged to Virtual Memory (VM) on the hard drive. You do need a hard drive with a system partition (C:\) big enough to hold your OS and the VM space. For WinXP a 20GB drive is "marginal." On a $/bit basis, 80GB to about 160GB drives are the current "cost effective sweet spot," but 250GB drives are not much more expensive ($/bit). Get as large as you can afford (within reason). With WinXP, unless you want multi-OS capability, the is NO GOOD REASON to partition your hard drive into smaller chunks, although you can if you wish. Since, by design in WinXP, VM is in the System partition, and is limited to 10% of the free space there, you should have a reserve free space of at least a couple of GB for VM. You can change which partition holds the VM, and what percent of free space may be used, but it is NOT RECOMMENDED by Microsoft, apparently for some fairly good reasons.

Since the EIDE controller that runs most installed drives can have only 4 outputs, you should not rely on being able to drop in another Hard Drive later. Most new machines will have a floppy drive, hard drive, CD-ROM (or DVD/CD-ROM) and CD-R/W (or DVD/CD-R/W) drive. Your EIDE ports are used up. Although you can add another EIDE card - if you have available and accessible free slots, most people have found it more convenient to use external (USB or FireWire) hard drives if more space is needed. Although USB and FireWire are "pretty fast" external drives typically are slower (about 4X?) than internal ones. (But not as much slower as the internal drives used in most laptops, which take typically about 10X as long to access new reads when compared to desktop internal hard drives.)

Read the "minimum requirements" for the OS you intend to use. Multiply everything by 2 if you really want the thing to work usably. Multiply everything by 2 again (4x total) if you want it to run "comfortably."

And NEVER CONNECT TO THE INTERNET without an up-to-date ANTIVIRUS and a FIREWALL.

Recent test showed an average "time to infection" of less than 20 minutes for unprotected machines. You likely want to use your machine, not spend all your time repairing viral crud infections. Anti-Spware, Anti-Popup, and Anti-Hijack stuff are separate things, and almost necessary; but they need to be tailored to the threats you might run into and to what you find objectionable.

Purely opinion. Subject to change - except the need for AV.

John

Subject: RE: BS: Virtual or physical memory
From: GUEST,Jon
Date: 09 Nov 04 - 05:23 PM

John, I've not come accross a floppy drive that uses the HD EIDE. All the mother boards I've had have a separate FD controller. The cables are different too. The FD one is wider than the EIDE.

As for need for AV... I think said so before but I was one who did get caught in the sort of 30 min time period... Thought I'd be safe doing a couple of other downloads first...

Subject: RE: BS: Virtual or physical memory
From: GUEST,computer cretin
Date: 18 Dec 08 - 08:50 AM

I have a problem....one of my son's friends appears to have used up all the virtual memory on my computer (a compaq) and now I can only get to safe mode but even that is dark so I can not fix anything. I get the screen with safe mode in each coerner but nothing else and I can't make it go. Any suggestions?

Subject: RE: BS: Virtual or physical memory
From: Amos
Date: 18 Dec 08 - 09:20 AM

Yes. Give the machine to your son to fix and get yourself a Mac.


A

Subject: RE: BS: Virtual or physical memory
From: McGrath of Harlow
Date: 18 Dec 08 - 09:25 AM

I suppose for human beings virtual memory is on our bookshelves and also these days in Google.