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Author Topic: Very basic RAM question 133 vs 2700  (Read 6226 times)

nickbirkby

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Very basic RAM question 133 vs 2700
« on: December 11, 2022, 06:17:27 AM »

Hello all,
This afternoon I have been trying to max out my MDD 2003 1.25 with 1.5gig of RAM. I have been going through what Ram I have in different machines and discovered that its almost all PC133 and not the PC2700 that is supposed to be the optimal for this machine.

So I now have one stick of 512m 2700 ram and the rest is PC133 making up 1.5gig. Works fine so far.

My question is this: is the difference in performance very significant between the two? I am keen to use the correct spec of course.

Sorry its a rather basic question, but I'm not that clued up on this and am now curious. Thanks so much.
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robespierre

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Re: Very basic RAM question 133 vs 2700
« Reply #1 on: December 11, 2022, 12:20:16 PM »

The numbers aren't measuring the same thing. PC133 means 133 MHz. PC2700 means 2700 MB/s (in fact it's only 2666.66).
The latter has a higher clock speed (166.66 MHz) but more importantly it is Double Data Rate, so it transfers twice per clock cycle.
So yes, there is a large difference in potential performance, but I can't say whether that will matter on the MDD.
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GaryN

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Re: Very basic RAM question 133 vs 2700
« Reply #2 on: December 11, 2022, 03:32:40 PM »

So I now have one stick of 512m 2700 ram and the rest is PC133 making up 1.5gig. Works fine so far.
I'm puzzled. AFAIK, PC133 RAM is typically a 168-pin SIMM while the PC-2100 or PC-2700 found in the MDD are 184-pin.
So I'm not sure how you can have the PC-133 installed and working…?

The PC-133 was common in the Quicksilvers with their 133MHz data bus.
The MDD's have either a 133MHz bus in the 867MHz and 1.0GHz machines or a 167MHz bus in the faster ones.
So, your (either) single or dual 1.25MHz machine wants PC-2700.
   * You can also use PC-3200. It will work fine though it will run at PC-2700 speed.
The optimum config for the MDD is four 512Mb PC-2700 SIMMS.
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Protools5LEGuy

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Re: Very basic RAM question 133 vs 2700
« Reply #3 on: December 11, 2022, 03:43:54 PM »

I am in front of my MDD 867 dual and Apple System Profiler says

DIMM 0 PC 2600U-30330

DIMM 2 PC133 CL3

DIMM 3 PC133 CL3

All 512 DDR AFAIK

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nickbirkby

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Re: Very basic RAM question 133 vs 2700
« Reply #4 on: December 11, 2022, 09:17:50 PM »

Thank you for the replies. Its a bit confusing but I get the idea. To be clear the machine is a single processor 1.25 built 2003 and it shipped with PC2700

Im assuming the machine has a 167mhz bus, so I am 37 mhz under spec. :)

GaryN the 133 ram appears physically identical to the 2700 as far fitting the slots goes.

The PC2700 ram seems a little scarce/ expensive - at least where I live, but I can add 3200 to my options then.

Last rather newb question, if Im changing ram around in machines is there any wisdom in doing a p-ram reset on startup with a new config of ram? (conltrol-alt-p-r) Or is that just for if there is a problem with booting?

Thanks again.



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refinery

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Re: Very basic RAM question 133 vs 2700
« Reply #5 on: December 11, 2022, 11:37:03 PM »

it could just be a case of some poor choices in labeling. PC133 typically refers 133mhz SDR memory, but if you wanted to be semantic about it, DDR-266 technically is still 133mhz ram, it just processes data at double the rate, hence 266.
not unusual for something like that to happen when a new standard comes out and not everyone is adhering to it fully yet.
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GaryN

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Re: Very basic RAM question 133 vs 2700
« Reply #6 on: December 12, 2022, 02:14:57 PM »

I am in front of my MDD 867 dual and Apple System Profiler says DIMM 0 PC 2600U-30330
On the MDD, ASP has a bug that reports PC2700 RAM as PC2600, which doesn't exist.
PC133 is the clock speed which is correct for a 867MHz MDD

So I now have one stick of 512m 2700 ram and the rest is PC133 making up 1.5gig. Works fine so far.

So, nickbirkby… I see you have now added:
"GaryN the 133 ram appears physically identical to the 2700 as far fitting the slots goes."
Thank you for that. I was really scratching my head because you went back and edited out the original statement about pin count on those SIMMS.  ;D

It's no necessary to reset the PRAM after changing the memory sticks. The system will recognize it by itself.
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nickbirkby

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Re: Very basic RAM question 133 vs 2700
« Reply #7 on: December 12, 2022, 11:05:37 PM »

Thanks GaryN for clearing up the Pram reset question.
Btw, I didnt actually mention the simm pin count on the original post, I forgot. :)

Im now going to try and cobble together a mix of 3200 and 2700 and see how it goes.

Thanks to all for the replies, much appreciated  :D
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