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MP 7,1 Mac Pro 2019 CPU Upgrade, RAM even after PRAM Reset still at 2666 MHz despite using 2933 DIMMs

Dt990

Dt990

macrumors member
Original poster
Jan 24, 2020
57
28
Oregon
Previous with my 8-Core CPU I had bought all 2933 R-DIMMs for when it came time to upgrade, and here I am, with a w3245m.

Is there a trick I'm missing for getting a Mac Pro 2019 to re-register it's RAM after a CPU upgrade to 16-Core? With the old cMPs 5,1, when upgrading, you could bump the 1066 to 1333 if you had the correct DIMMs.
 
Dt990 said:
Tried that, gotta do 4 DIMMs and I have 4 x 32 GB and it's all 2933 Mhz, still 2666
Click to expand...

Did you try the 1 DIMM configuration, and test each DIMM individually to make sure your processor can support ANY DIMM at 2933?

If you want to test any single channel or the DIMM itself, you can use a 1 DIMM configuration by installing a single DIMM into the first slot of a channel. If you want to test the second slot of a channel, install DIMMs into both slots of a channel.
Click to expand...
 
I had to check the CPU spec. As Apple use the W-3245, not the W-3245m version. But it looks ok, and supporting 2TB RAM.

Since you are having issues with the memory timing, with the sticks you purchased.
I would test with the original Apple memory that the machine came with. Apple sold 2933 MHz ram in the 8-core models as well. Even if the CPU only supports 2666 MHZ. So it should run at full speed with any CPU upgrade.
 
mattspace said:
Did you try the 1 DIMM configuration, and test each DIMM individually to make sure your processor can support ANY DIMM at 2933?
Click to expand...
Unless I'm severely mistaken, it won't boot with a single DIMM as it requires dual channel.
Regulus67 said:
I had to check the CPU spec. As Apple use the W-3245, not the W-3245m version. But it looks ok, and supporting 2TB RAM.

Since you are having issues with the memory timing, with the sticks you purchased.
I would test with the original Apple memory that the machine came with. Apple sold 2933 MHz ram in the 8-core models as well. Even if the CPU only supports 2666 MHZ. So it should run at full speed with any CPU upgrade.
Click to expand...
Yeah, I have the original two factory DIMMs. The goofy part though is the rest is Crucial and reads 2933 MHz.

Open up my 2019 is just an exercise in frustration when I have to unplug a torrent of cables each time, and it's a slow boot. The CPU is a QS since I decided to roll the dice and pay about $250 for it, right now wondering if that's just the issue of the quality sample.

When I tried only the 32 GB DIMMs I zapped the PRAM twice for good measure. There's always the SMC reset but I'm convince that's a placebo and it should be SMC resetting each time I unplug it.
 
Well, single DIMM was able to hit 2933 MHz, although needed to be in the correct slot. Top most for anyone who wonders. Got the ol orange blinky light yesterday when I didn't bother to move the DIMM.

Was able to do that with both my factory and Crucial RAM. Buuut at least one fo the DIMMs does not operate at 2933 MHz. I didn't have time to test every individual DIMM as the Mac Pro 2019 is a tragic pain the ass as it requires opening and closing for each successive boot.

Pretty cool that at least one of my Crucial chips is mislabeled as ALL are listed as 2933 MHz.
 
Dt990 said:
I didn't have time to test every individual DIMM as the Mac Pro 2019 is a tragic pain the ass as it requires opening and closing for each successive boot.
Click to expand...

It's annoying, but it also means you can't short anything by having live power, even from signalling to peripherals, active during hardware changes.

There's a logic to it, annoying as it may be. Just get masking tape, and make tags around every cable, stating what port it has to connect to.
 
It's still madness. I've done some pretty slapdash things over the year, like accidentally unplugging PCIe and PCI cards while a computer is on, plugging ATA drives while a computer is powered and never has it caused a problem. I already have my cables tied but it's still an annoyance.

I did manage to find a singular Crucial DIMM that only runs at 2666 MHz. My two Apple 16 GB DIMMs and the two 16 GB OWC ones are all 2933 MHz.

I'll buying one again from Crucial and then returning this one as I feel miffed that I was sold a DIMM directly from them that isn't as advertised and never had a chance to test it otherwise until I upgraded. It's unlikely that I'll notice any difference.
 
Dt990 said:
I'll buying one again from Crucial and then returning this one as I feel miffed that I was sold a DIMM directly from them that isn't as advertised and never had a chance to test it otherwise until I upgraded. It's unlikely that I'll notice any difference.
Click to expand...

Honestly, OWC RAM for this machine is cheap enough that you're going to waste more time chasing Crucial than you'll save. Just ask Crucial for a refund on the out-of-spec stick, or write it off as a learning experience.
 
Dt990 said:
It's still madness. I've done some pretty slapdash things over the year, like accidentally unplugging PCIe and PCI cards while a computer is on, plugging ATA drives while a computer is powered and never has it caused a problem. I already have my cables tied but it's still an annoyance.

I did manage to find a singular Crucial DIMM that only runs at 2666 MHz. My two Apple 16 GB DIMMs and the two 16 GB OWC ones are all 2933 MHz.

I'll buying one again from Crucial and then returning this one as I feel miffed that I was sold a DIMM directly from them that isn't as advertised and never had a chance to test it otherwise until I upgraded. It's unlikely that I'll notice any difference.
Click to expand...
Hi Greg,
I follow your youtube Channel and blog and I want to contribuate and add something about the Mac Pro 7.1
(and definitive upgrade guide)
the chipset ASM2812 allows bifurcation and I just bought a GLOTRENDS PA20 2 Ports card for Mac OS and windows 11 (one system on each nvme)
this card is very cheap (about 80 $ with black friday price) compared to other chipsets
I don't know if everything will be ok for a long time, but for the moment, it works !
 
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