Older (1.1) Mac Pro runs SLOWER with RAM upgrade.

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John20904 Author

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Older (1.1) Mac Pro runs SLOWER with RAM upgrade.

I have an older Mac Pro. I've been running it with 8 megs of RAM until just recently. RAM boards included original 4x512K chips that came with machine, plus 1Mb chips I had added, so I was using all 8 slots to get only 8MB of RAM. Bought 4x2mb to put in slots previously taken with the 512 chips, so new total would be 14Mb.

With new RAM installed (14MB total) the machine ran slower. One thing I noticed is that when the full 14mbs were installed, even though the systems saw them just fine, the additional memory was not being used, according to Activity Monitor - apps like Lightroom and Photoshop were absolutely crawling, but LOTS of free ram showing on the monitor.

All else being equal - plenty of HD space, etc- removing the additional ram restored its previous performance. Now, instead of both RAM boards, I'm just using one memory board with the newer 4x2 Mb modules, totaling 8 mb RAM, while the second board holding older chips worth 6MB sits on my desk. Performance is better but gosh darn it I'd really like to use, and benefit from, the additional 6mb of RAM!

What the heck?

MacPro, Mac OS X (10.4.8)

Posted on Nov 25, 2015 9:36 AM

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Answer 1

John20904 Author

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Nov 25, 2015 9:38 AM in response to John20904

I'm running 10.7.5, btw, not 10.4.8

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Answer 2

lllaass

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Nov 25, 2015 9:42 AM in response to John20904

What are the specs on the new sticks?

Where are you looking to see if they are recognized?

When running slow open System Profiler

OS X: About System Information and System Profiler - Apple Support

and see if OK is listed by all sticks

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Answer 3

John20904 Author

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Nov 25, 2015 9:55 AM in response to lllaass

System profiler showed new sticks OK, and Activity Monitor showed 14MB available.

In fact, it's the NEW sticks that are running now, all on one board, while the second board sits on my desk. I've tried the sticks in various combinations, and the outcome is the same - both boards with 14MB slower, one board with 4x2MB, better. Hence my total confusion. Whatever is wrong, it doesn't seem to be the memory sticks.

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Answer 4

lllaass

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Nov 25, 2015 9:56 AM in response to John20904

Again:

What are the specs on the new sticks?

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Answer 5

John20904 Author

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Nov 25, 2015 10:43 AM in response to lllaass

New sticks are

Size: 2 GB

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Answer 6

John20904 Author

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Nov 25, 2015 10:44 AM in response to John20904

2GB PC2-5300 ECC FBDIMM CL5

x4

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Answer 7

Nov 25, 2015 6:14 PM in response to John20904

I was using all 8 slots

When you can fill all slots, that Mac switches to a double-wide memory access. This can improves speed by 10 to 15 percent.

Where is The hatter ? That is his line.

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Answer 8

John20904 Author

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Nov 25, 2015 6:33 PM in response to Grant Bennet-Alder

Thank you, that would be my expectation as well, but as you may see in my original post, I am in fact experiencing slower performance with all slots filled. Hence my confusion and my question.

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Answer 9

Nov 25, 2015 6:35 PM in response to John20904

Though you had removed one of the Riser-cards. That is not all slots filled.

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Answer 10

John20904 Author

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Nov 25, 2015 7:05 PM in response to Grant Bennet-Alder

Sorry if my original post was unclear. Here are the 2 configs I've been wrestling with today:

Config A - 14MB: 6x2MB +1MB+1MB -- All 8 slots filled, 14MB RAM total, results SLOW, with all sticks checking out in System Profile, but Activity Monitor clearly showing that most of the RAM is not being used even while apps CRAWL.

Config B - 8MB: 4x2MB, all in one riser card, results MUCH BETTER, noticeably faster performance in all apps. Activity monitor shows normal use of RAM, peaking during high activity and going back to normal, etc.

Exactly the opposite of what I would expect, which is the reason for my question. It's as if the additional RAM is slowing the computer down but not being used, which does not make any sense.

Plenty of room on HD - I have 4 x2TB internal working drives with one drive set aside for working space, more than 1.2G available for cache, scratch disk, etc

Thoughts?

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Answer 11

lllaass

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Nov 26, 2015 1:06 AM in response to John20904

It appears that the new memory is not compatible with the old memory. That happens sometimes.

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Answer 12

Nov 26, 2015 8:11 AM in response to lllaass

Is it possible that the old RAM was 800, and the new RAM is 667?

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Answer 13

John20904 Author

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Nov 26, 2015 8:30 AM in response to Grant Bennet-Alder

No, it's all 667. I've double and triple-checked for all the explanations I can think to check.

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Answer 14

lllaass

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Nov 26, 2015 9:30 AM in response to John20904

Who made the old RAM
Who made the new RAM?

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Answer 15

John20904 Author

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Nov 26, 2015 10:06 AM in response to lllaass

I think I discovered the problem, and it has nothing to do with the RAM. The 2007 CPU is just too feeble for the 2015 apps I'm running. In Activity Monitor I can see that the CPU is maxed out by the processes I'm trying to do; I think having more RAM installed actually makes it worse, the additional RAM causes the CPU to work harder compared to having less RAM and therefore more VM/scratch disk hits. Having to use VM seems to ease the load on the CPU, although it should be slower to do so, the CPU doesn't show as much burden with less RAM; With more RAM, the CPU is getting maxed out, so the processes are actually slower.

Happy Thanksgiving!

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