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Debugging a RAM upgrade and slow OS X performance Install
[Editor's note: Here's a story of a user experience with a RAM upgrade that was anything but normal. If you upgrade your RAM at some point in the future and are faced with extremely slow system performance, you may want to remember this article's suggested fix...]

I recently installed additional RAM in my G4 450DP running OS X v10.0.4. I went from 640MB (128MB + 2x 256MB DIMMS) to 1128MB by adding a single 512MB DIMM. The installation was NOT routine.

The system ran normally before installation. After installing the DIMM, all system operations were noticeably slow. The boot process took longer than normal and even the insertion point in the login window blinked at a dramatically slower rate than normal. I could type my username and password blind and not see the character echo for close to 2 minutes.

Once logged in, all my login apps would attempt to start and then quit prompting the standard system message. It would take about 3-5 minutes between each app to get the quit-message. At no time was I able to do anything useful in any application. The system was just too slow. The pointer did move as fast as normal...the system was just unresponsive to clicks or drags.

Read the rest of this article for more detail on the troubleshooting Alex did, and his eventual solution...along with a question about why this happened.

I began to try to solve the problem by removing the just-added DIMM. Next I tried the new DIMM by itself. Next I tried just the original 128MB DIMM. I tried several different variations of new DIMM only, old DIMMs only, old + new DIMMs, and various slot assignments. All attempts ended in the same behavior--slow boot-up, slow login, slow application loading, unusable system.

OK, try some more serious things: I zapped PRAM the normal way (CMD-CTL-P-R) without noticeable affect. Finally, I got out the tactical nuke: I pulled the chassis from my shelving unit and set it out on a work platform. I pulled the motherboard battery and pressed the internal reset button. I left the battery out 30 minutes and worked on my iBook.

At one point in this exercise I looked at my iBook and thought, "Looks like this is my only working computer" and I was wondering if Apple would honor a AppleCare renewal I'd just mailed the previous day. :(

But...that fixed it. The system came up normally as if nothing had happened.

I don't understand the relationship between OpenFirmware and the kind of hardware change I made but clearly I had to do a drastic thing to my system to work properly.

Can anyone clue me in as to why I had to do what I did? How about other things I might have tried?

Thanks.
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Too much RAM?
Authored by: friedmaj on Aug 07, '01 11:57:24AM

Isn't there a max of 1 GB of RAM allowed?



[ Reply to This | # ]
Too much RAM?
Authored by: aalegado on Aug 07, '01 01:20:12PM

The addressable-RAM limit is actually 1.5GB. Every G4 since the G4 AGP has the 1.5GB ceiling. The G4 PCI which preceded the G4 AGP was the G4 that used a modified G3 Yosemite ("Blue & White") motherboard and so shared the Yosemite's 1GB limit.

The thing about the limit is that until the G4 Digital Audio and G4 Quicksilver models (funny that the "G4 Digital Audio" wasn't called the "G4 2001" despite the fact that it was introduced at the start of 2001), G4s had 4 DIMM slots like the G3 Blue & Whites before it. So, like some older pre-PowerPC Macs, you could put more physical RAM In than the system would recognize. The Digital Audio and Quicksilver G4s have 3 DIMM slots so you can't do that but, and, at the same time, you lose some flexibility with the composition of your RAM.

My G4 has a 128, 2 256's, and a 512--a patchwork of capacities. A 3-slot does't let you Frankenstein your way to a a high RAM complement...if you want a lot of RAM, eventually, you have to throw something out. Of course, with 512MB DIMMs selling for $70 (give or take, mine costs $73.50 before shipping), you can afford to buy 1.5GB without killing the piggy bank.



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isn't resetting the motherboard a normal procedure
Authored by: spyro_le_dragon on Aug 08, '01 04:19:16AM

Isn't it required to reset the motherboard whenever you change the RAM config?
(it is when you add/remove PCI cards).
I am pretty sure people rarely do that for the RAM, but I think it is written
somewhere in the manual, may be in the troobleshooting pages. (But who reads
that?)



[ Reply to This | # ]
isn't resetting the motherboard a normal procedure
Authored by: aalegado on Aug 08, '01 11:56:28AM

I was not aware of that requirement but on this same machine, when I went from 128MB to 384MB and again from 384MB to 640MB (both times by adding a 256MB DIMM) I did not have to do anything apart from adding the RAM. The only difference between those past upgrades and this one was that this one was done after OS X was installed. The last 256MB DIMM went in in January which predates the OS X release by several months.



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isn't resetting the motherboard a normal procedure
Authored by: aalegado on Aug 08, '01 12:07:09PM

I neglected to address your point about the PCI cards: Again, on this same machine I have not had to reset the motherboard when adding PCI cards. I've added and removed video and SCSI cards from this machine without having to resort to resetting the motherboard. In fact, this is the first time since purchase that I've had to take these drastic steps to restore system operation.

I checked the manual that came with my G4 and there is no mention of the motherboard reset switch nor is there an indication of its location in any of the illustrations of the computer. Specicically, the sections about adding/removing PCI/AGP cards, RAM, and the battery do not mention nor illustrate the location of the switch.

The troubleshooting section does have an entry about a system that won't start properly. It does mention the PRAM trick which I tried after trying DIMM installation combination variations but, again, it does not mention the motherboard reset switch.

This seems to indicate that use of the switch is reserved for service technicians and not for end-users.



[ Reply to This | # ]
Added another 512MB...
Authored by: aalegado on Oct 23, '01 01:00:27AM

With prices so low ($59 in this case) I added a second 512MB DIMM just because. I was curious as to whether I'd encounter the same problem as before when I had to resort to resetting the motherboard to get it to recognize the first 512MB DIMM.

This time around the DIMM went in without a hitch. My system now has 1.5GB composed of 2 256MB DIMMs and 2512MB DIMMs. Those latter two happen to be the exact same model from the exact same manufacturer but purchased from two different vendors and are PC133 devices with 2-2-2 timing.

I'm running OS X 10.1 and have not noticed any performance improvement which tells me that for my mix of apps and processes, 1.1GB is sufficient. What strikes me is that my system still uses a swapfile albeit only one where, in the distant past (10.0 through 10.0.2) I've noticed two or even three 80,000,000 block swapfiles.



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