Memory: DIMMO/J21, J22, J23 Readouts

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Level 1

7 points

Memory: DIMMO/J21, J22, J23 Readouts

The original stick is a Samsung 256 K4S280832A-TC75 and DIMMO/J21 reads PC133-333. In the J22 and J23 slots the sticks are Micron Tech 512 48LC32M8A2-7 EC and read PC100-322S. The MTs were sold to me as PC133 CL2. Everything works OK, but I'm puzzled at the different readouts. Any explanations?

G4 QS Dual 1 GHz, Mac OS X (10.5.6), 1.25 GB SDRAM

Posted on Mar 21, 2009 10:48 AM

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Answer 1

Jeff

Level 6

12,328 points

Mar 21, 2009 7:23 PM in response to ocdownhiller

The speed for PC-133 chips would either be 7 or 7.5 nanoseconds, so you'll see -7 or -7.5 (-75) printed on them. If you see -8 or -08, the chips are technically rated for PC-100. Micron Technology makes a quality product with rigorous testing, so some discount memory manufacturers feel that they can safely overclock the Micron chips (although Micron's spec sheet for the chips doesn't recommend it), knowing that they'll probably perform OK. I once returned some K-Byte DDR memory to Best Buy for that reason. K-Byte was selling "PC-3200" memory, having slightly slower Micron chips designed for "PC-2700" usage. As for your Quicksilver, the best SDRAM would be PC-133 CL-2 (2-2-2), which Micron did manufacture.

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Answer 2

Mar 23, 2009 2:49 PM in response to ocdownhiller

Your QS RAM operates at 133MHz. What's strange is that the MT modules are read as PC100. PC133 RAM will operate in a 100MHz Mac (at 100MHz speed), but I've never seen PC100 RAM operate in a 133MHz Mac. Is the info you are providing listed in the System Profiler?

CAS latency (sometimes shortened to CL) is a measure of how fast the first byte of info gets in and out of a RAM module. There are CL2 and CL3 DIMMs. CL2 means that it takes two processor cycles to get the info in and out; CL3 take three cycles. Although the speed boost is imperceptible as it affects only the first byte. When memory is listed with hyphens (ex., 2-2-2; 3-2-2) the first number is CAS latency.

Look at this link: *Testing RAM* @ http://guides.macrumors.com/Testing_RAM Then download & use Memtest & Ramber.

 Cheers, Tom 😉

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Answer 3

ocdownhiller Author

Level 1

7 points

Mar 23, 2009 3:52 PM in response to Texas Mac Man

Thanks for the response.
The readouts are from the System Profiler.
Yesterday I pulled the 256 DIMM (which the SP identified as PC133-CL333) from DIMMO/J21 and replaced it with another 512 DIMM from the same vender that sold me the original two DIMMs (I've got 2 QSs). All three 512 DIMMs read PC100-CL322 in the SP.

Like you said, a PC100 DIMM should not be working in the QS, but I've never had any RAM related problems in either machine. I have done some extensive online research on RAM, so I'm familiar with what you and Jeff have written. Micron Tech stuff is reputed to be high quality. I've looked up the part numbers on the DIMM chips from both the Samsung and MT sticks, and both company's facts sheets on the chips indicate they are PC133 CL2. So, I'm puzzled!

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Answer 4

Mar 23, 2009 5:17 PM in response to ocdownhiller

Why don't you contact the supplier(s) & see what they say.

 Cheers, Tom 😉

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Answer 5

ocdownhiller Author

Level 1

7 points

Mar 26, 2009 10:12 AM in response to ocdownhiller

I think I've figured it out. Using an older MacOS 9 application, DIMM First Aid, gives me a reading on all the 512 MT DIMMS as PC133-222, what they should be.

Techs at a repair shop I've used over the years, MacShop Northwest, opine it's a combination of a week application in the System Profiler and some poor feedback from the system bus.

Go figure.

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