Older AM3 CPU on AM3+ MB. What's the Maximum RAM frequency?

[01i]

I currently have a AMD Phenom II X2 545 3.0 GHz AM3 CPU in a Foxconn A7VMX-K Motherboard.

I'm looking to upgrade, but my main reason for upgrading my is to increase beyond the 4GB of RAM that I am currently maxed out with. Cash is tight at the moment, so ideally I want to replace as little as possible.

I am considering upgrading the MB to an Asus M5A97 R2.0, which seem to be my best option for increasing my RAM while maintaining backward compatibility with the existing components in the PC. As far as I can tell, buying this MB means that I can avoid replacing everything except the MB and RAM.

The question is, what RAM to I buy?

According to the specs I can find online for my existing CPU, the 545 supports DDR2 (up to 1066 MHz) when used in an AM2+ MB (like it currently is), and supports DDR3 (up to 1333 MHz) in an AM3 MB.

However, the AM3+ boards didn't exist when the CPU was still in the market, so I can't find any information about what would be supported on an AM3+ MB.

Would I be limited to PC3-10600 (1333 MHz) RAM that the 545 supported on an AM3 board? Or could I make use of the faster AM3+ RAM speeds supported by the Asus M5A97 R2.0 e.g. 1600 MHz or 1866 MHz?

 

[Aeacus]

It's not the CPU that limits the RAM speed but the MoBo itself. Having faster RAM in your system, e.g 1866 Mhz means that only the CPU uses the RAM at speeds of which it's rated for (1333 Mhz) while the rest of your components use the full speed of the RAM.

An example:
In my Skylake build (full specs with pics in my sig), i have Intel's i5-6600K. The CPU has RAM speed limited to DDR4 1866/2133 Mhz while my Kingston DDR4 RAM is rated for 3000 Mhz and i have it also running at 3000 Mhz.
CPU specs: https://ark.intel.com/products/88191/Intel-Core-i5-6600K-Processor-6M-Cache-up-to-3_90-GHz
(read Memory Type under Memory Specifications)

Do note that when you're Win user and switch out your MoBo, you'll also need a new genuine Win license since Win licenses are tied to a MoBo.

 

[01i]

It's not the CPU that limits the RAM speed but the MoBo itself. Having faster RAM in your system, e.g 1866 Mhz means that only the CPU uses the RAM at speeds of which it's rated for (1333 Mhz) while the rest of your components use the full speed of the RAM.

An example:
In my Skylake build (full specs with pics in my sig), i have Intel's i5-6600K. The CPU has RAM speed limited to DDR4 1866/2133 Mhz while my Kingston DDR4 RAM is rated for 3000 Mhz and i have it also running at 3000 Mhz.
CPU specs: https://ark.intel.com/products/88191/Intel-Core-i5-6600K-Processor-6M-Cache-up-to-3_90-GHz
(read Memory Type under Memory Specifications)

Do note that when you're Win user and switch out your MoBo, you'll also need a new genuine Win license since Win licenses are tied to a MoBo.

Thanks. So it makes no sense to purchase 1333 when I can get 1866 on the board. Good to know.

Quick follow-up on the note about windows 10 license. I was under the impression that (post anniversary update) if I've linked my activation to a microsoft account, that I can use the activation troubleshooter to migrate the license after a major hardware change. Is that not the case?

https://support.microsoft.com/en-gb/help/20530/windows-10-reactivating-after-hardware-change

 

[Mark RM]

You can put 1866 RAM on the board that doesn't mean the memory controller on the 545 can run it at that speed, because that's where the memory controller is.

Default DDR speed for that CPU - 667 MHz Memory controller, So DDR3 1333 or slower. Sure faster RAM will install, but it will still run 1333 unless you OC it. In reality the changes in performance are minimal. I mean, a Phone SOC is a quite a bit more powerful than this CPU.

I bought a used mobo/i3/8 gigs for 75 bucks - it activated with Windows 10 home premium with a digital license . If I was that dead set on spending as little as possible I wouldn't buy anything for that rig I could avoid.

 

[01i]

If I was that dead set on spending as little as possible I wouldn't buy anything for that rig I could avoid.

I'll still want to pick up a new CPU (and Graphics card) when I can afford them. So would be happy to purchase better parts that will have better effect a few months down the line.

However, at the moment (while there are a lot of special offers around) the best prices I can find for decent DDR3 RAM, actually make it more cost effective to purchase 1866MHz that 1333MHz.

1333 MHz 16GB (2x 8GB) CL09 £142.64 HyperX FURY
1666 MHz 16GB (2x 8GB) CL09 £114.99 Corsair Vengeance Pro
1866 MHz 16GB (2x 8GB) CL10 £111.97 HyperX FURY
1866 MHz 16GB (2x 8GB) CL09 £127.49 HyperX Savage

As long as I can safely run 1866 MHz RAM on the processor, it's actually makes financial sense to do so.

I also found places suggesting that I wont want to run more than 1x 8GB DIMM per channel at 1333MHz on that CPU, and suggestions that I might want to underclock the RAM to 1333MHz and improve the CL score.

Could I purchase RAM that the MB can't handle (e.g. 2133/2400) and under clock it? Or would it not POST?

e.g.

2133 MHz 16GB (2x 8GB) CL11 £151.11 Corsair Vengeance Pro
2400 MHz 16GB (2x 8GB) CL11 £138.98 Corsair Vengeance Pro

I'm assuming that I could get to a pretty good CL score by underclocking that 2400 MHz CL11 RAM to 1333 MHz initially?

If it can be done, would it be worth the extra £27

 

[Mark RM]

It will post fine, RAM has a series of tables that the mobo reads for timings at different clock speeds. So if you shove 2400 RAM in there, there is a timing table for 1600 and 1333 for example...

https://i.stack.imgur.com/hvRQh.png

That ram in the image has timings in the SPD for various speed up to 1600Mhz, you are only see the last four, there are also entries in the table for three more lower speeds, the motherboard reads the table and sets the timings accordingly. So if the mobo requests timings for 1600Mhz off your 2400Mhz RAM, that's how it gets them.

I still wouldn't spend a cent on that platform. Work towards a B350 board, Ryzen, and DDR4 if you actually want an upgrade path or buy a good used combo from the classifieds, something I do a lot when people have limited budgets for me to build stuff for them.

But yes, what you are proposing would work.

 

[Aeacus]

Quick follow-up on the note about windows 10 license. I was under the impression that (post anniversary update) if I've linked my activation to a microsoft account, that I can use the activation troubleshooter to migrate the license after a major hardware change. Is that not the case?

https://support.microsoft.com/en-gb/help/20530/windows-10-reactivating-after-hardware-change

If you have a retail license of With 10 then yes, you can re-activate your license as stated in the link you shared. Though, that isn't possible when you have an OEM license.

As far as RAM goes, it's waste of money to buy faster RAM than your MoBo can support (2133/2400 Mhz DDR3), just so that you can underclock it.

Any RAM that you can put in your system are made so that they will run at the default speed, 1066/1333 Mhz for DDR3 and 2133 Mhz for DDR4, regardless the rated speed of the RAM. To get the rated speed of the e.g 1866 Mhz DDR3 RAM, you need to enable the XMP (for automatic RAM OC) or manually OC the RAM.

I'd go with 1866 Mhz RAM since even when you can't get it running at 1866 Mhz and would be stuck with 1333/1600 Mhz, it's still cheaper than going with 1333/1600 Mhz RAM. Btw, Kingston HyperX Savage series RAM is great RAM due to the low CAS latency it has. I also have Kingston HyperX Savage RAM in use in my Skylake build but mine is DDR4 (full specs with pics in my sig).

 

[01i]

Just went to purchase my RAM, and quickly went from slightly disappointed, to smiley face

The £111.97 1866 MHz CL10 HyperX Fury in my Amazon cart had gone out of stock, but when I went to find the £127.49 1866 MHz CL9 HyperX Savage I found 1600 HMz CL7 G.Skill Trident-X for £100 instead

 

[Mark RM]

sounds good, good luck!