Max SDRAM clock

I swear when I looked at LPC17xx a while back it had the max SDRAM clock at 60Mhz but Joe just tested G120 with 120Mhz SDRAM clock and it worked perfectly fine. Then we went back to datasheets I am not finding the 60Mhz limit anywhere anymore!!!

What is really nice here is that once SDRAM is 120Mhz, G120 runs almost 3 times as fast as EMX. Anyone of you guys know the answer to this? Is max SDRAM 60Mhz or it can safely run at 120Mhz?

i think you are right GUS:
this is what i found…

EMC of the LPC1788 is only rated to 80MHz not 120MHz and the EMC clock is feed from the CPU clock not the MUX. This means that when your CPU is running at 120MHz the max your EMC can run at is 60MHz (CPU/2)…

and here is a link for testing:


It is 80MHz.:

Hi Gus,

here is a thread discussing the exact same this you are after with responses from NXP:

Hopefully they can make up their mind as it seems they are confused… so i’m pretty sure your eye didn’t trick you…

I was praying I am wrong! Oh well, we will give you guys a peice of code to overlock at your own risk. It is pretty awesome running at 120mhz :wink:

'The Master Router" :slight_smile:

On a board that has been routed well, 120 should be possible. If Gus has seen it run stable at 120Mhz, it just shows the quality of the G120 :slight_smile:

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As @ Joe has said the max is 80MHz for SDRAM, if one uC works at 120Mhz it does not mean they all will.@ Gus should get a +1 for the G120 layout.

@ GUS- Could you leave an option to run the SD memory at 120MHz at risk?

Gus talked about a piece of code to overclock the ram, I think it’s a matter of changing the prescaler by writing a register.

@ WouterH I was looking at the Argon1, and if i am reading correctly, they are running SD ram at 120MHz.

If the datasheet says 80mhz max, then it’s a bad idea to ship units with clock set to 120mhz. Maybe they are using faster chips?