Why does Mac get slow after memory upgrade?

One important and unasked question is: how much free space is left on the HDD? As you might know, all modern OS's use virtual memory. This maps the real RAM onto a space taken from the hard disk, called the swap area. In consumer-type OS, that space corresponds to a regular file that competes with the rest of the files for room (server-type OS can map the space to a dedicated partition and doesn't have to compete).

So, if the disk is already full-ish, and you suddenly doubled the space needed for the virtual memory swap area. Now it has to go scrounge up at least 8GB of room on the drive. This happens every time, cause the paging area gets reinited at each reboot.

It gets more complex than that with an OS like ours (can have more than one swap area), but this should give you the idea.

Boot time is slower because it takes longer to verify the installed memory. If you have other slowdown problems then they aren't caused by the memory installed. Memory is memory. It doesn't matter who makes it. What does matter is if you purchased memory that doesn't have the specs required for your computer and described in the Adding Memory section of your user manual.

Then your slowness issue has nothing to do with memory. You can try this:

First, boot into Safe Mode and do this:

Repair the Hard Drive and Permissions

Boot from your Snow Leopard Installer disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list. In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive. If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the installer.

If DU reports errors it cannot fix, then you will need Disk Warrior and/or Tech Tool Pro to repair the drive. If you don't have either of them or if neither of them can fix the drive, then you will need to reformat the drive and reinstall OS X.

Restart normally. See the following for more maintenance:

Kappy's Personal Suggestions for OS X Maintenance

For disk repairs use Disk Utility. For situations DU cannot handle the best third-party utilities are: Disk Warrior; DW only fixes problems with the disk directory, but most disk problems are caused by directory corruption; Disk Warrior 4.x is now Intel Mac compatible. TechTool Pro provides additional repair options including file repair and recovery, system diagnostics, and disk defragmentation. TechTool Pro 4.5.1 or higher are Intel Mac compatible; Drive Genius is similar to TechTool Pro in terms of the various repair services provided. Versions 1.5.1 or later are Intel Mac compatible.

OS X performs certain maintenance functions that are scheduled to occur on a daily, weekly, or monthly period. The maintenance scripts run in the early AM only if the computer is turned on 24/7 (no sleep.) If this isn't the case, then an excellent solution is to download and install a shareware utility such as Macaroni, JAW PseudoAnacron, or Anacron that will automate the maintenance activity regardless of whether the computer is turned off or asleep. Dependence upon third-party utilities to run the periodic maintenance scripts had been significantly reduced in Tiger and Leopard. These utilities have limited or no functionality with Snow Leopard or Lion and should not be installed.

OS X automatically defragments files less than 20 MBs in size, so unless you have a disk full of very large files there's little need for defragmenting the hard drive. As for virus protection there are few if any such animals affecting OS X. You can protect the computer easily using the freeware Open Source virus protection software ClamXAV. Personally I would avoid most commercial anti-virus software because of their potential for causing problems.

I would also recommend downloading the shareware utility TinkerTool System that you can use for periodic maintenance such as removing old log files and archives, clearing caches, etc. Other utilities are also available such as Onyx, Lion Cache Cleaner, CockTail, for example.

For emergency repairs install the freeware utility Applejack. If you cannot start up in OS X, you may be able to start in single-user mode from which you can run Applejack to do a whole set of repair and maintenance routines from the commandline. Note that AppleJack 1.5 is required for Leopard. AppleJack 1.6 is compatible with Snow Leopard. There is no confirmation that this version also works with Lion.

When you install any new system software or updates be sure to repair the hard drive and permissions beforehand. I also recommend booting into safe mode before doing system software updates.

Get an external Firewire drive at least equal in size to the internal hard drive and make (and maintain) a bootable clone/backup. You can make a bootable clone using the Restore option of Disk Utility. You can also make and maintain clones with good backup software. My personal recommendations are (order is not significant):

Backuplist

Carbon Copy Cloner

Data Backup

Deja Vu

iBackup

JaBack

Silver Keeper

MimMac

Retrospect

Super Flexible File Synchronizer

SuperDuper!

Synchronize Pro! X

SyncTwoFolders

Synk Pro

Synk Standard

Tri-Backup

Visit The XLab FAQs and read the FAQs on maintenance, optimization, virus protection, and backup and restore.

Additional suggestions will be found in Mac Maintenance Quick Assist.

Referenced software can be found at CNet Downloads or MacUpdate.

FrankFR wrote:

The speed since normal while booting, after the Mac becomes slow. The system information shows 8Gb well installed.

Perform a extended overnight Memtest using Rember, make sure it's a cold boot (after a shutdown) and startup programs are disabled so the memory is clear as possible. No screen saver or sleep enabled etc.

http://kelleycomputing.net/rember/

If the RAM is bad send it back. Sometimes you may need to clean the contacts with bit of rubbing alcohol.

If the RAM was bad it wouldn't pass POST.

I think that's the silliest thing I've ever heard. I have 8 GBs in my MP managed quite well by Snow Leopard. I don't know where you get these ideas, but you should visit a different library. I don't think you have any idea what you're talking about.

Lion is slower than Snow Leopard, so yes, going to Lion isn't going to help.

All I can suggest is to backup and reistall your OS to eliminate fragmentation/de-optimization and just general garbage that accumulates.

Sometimes a OnyX cache cleaning does wonders too.

Run all the intial tests, maintainance and then cleaning, then reboot at the end (must!)

http://www.titanium.free.fr/

Pretty good. My Lion MBP w/4GB RAM does its trick in 35 seconds flat, but doesn't autolaunch any applications, so you're in the ballpark again.

Bon appetit!

Sorry, mine is an #A1286: Oct'11 MBP, 2.4GHz, 4GB RAM, 15" Widescreen Display, 7200RPM 750GB HDD, purchased Dec'11. Running factory-installed 10.7.2, contents migrated from an old 10.5.7 MBP via Setup Assistant at first boot. Mention these details cause they all have an impact on performance and battery life.

Besides the 35-40 sec. startup performance, till now have not had the need to run it flat out to automatic forced sleep. But I have gone up to 5:45 hours w/40% charge still remaining, according to Energy Saver & Coconut Battery, so I'm confident it would probably go all the way to around 7-8 hours.