What is the actual Maximum Frequency supported by DDR3 in the Cyclone5 GT device?

[Sushmita]

Hello,

I want to run the RTL at more than 150Mhz for DDR3.

I tried to verify this in the parameter settings of the DDR3 controller Uni-phy IP used in the NIOS II Ethernet system example design. In the settings the maximum AFI clock frequency is mentioned as 150 MHZ.

I referred the below mentioned document, in this it is mentioned that the maximum achievable frequency for cyclone devices is 125 MHz.

Please refer: page - 243, "Table 7-1: Configuration Schemes and Features Supported by Cyclone V Devices" of the below document:

https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/hb/cyclone-v/cv_5v2.pdf

My query is as below:

1) What is the actual maximum achievable DDR frequency for cyclone 5 GT?

2) Let's say it is 150 Mhz for example, is it the final frequency that we can use or do we have to consider a safer value less than that?

Thanks and Regards

Susmita

[NurAida_A_Intel]

Hi @Ssrb​ ,

Welcome to Intel Community. Please allow me to address your query as below:

1) What is the actual maximum achievable DDR frequency for cyclone 5 GT?

 [Aida] :The maximum DDR3 frequency for Cyclone V GT is 400 MHz under speed grade C7 and I7. For more details , you may refer to this EMIF spec estimator tools and filter down based on your targeted specifications. --> https://www.intel.com/content/www/us/en/programmable/support/support-resources/support-centers/external-memory-interfaces-support/emif.html

2) Let's say it is 150 Mhz for example, is it the final frequency that we can use or do we have to consider a safer value less than that?

[Aida]: Yes, you can use less value than the maximum achievable frequency if that give you better performance. But, you must not exceed the maximum frequency allowed.

Hope this helps.

Thanks

Regards,

Aida

[Sushmita]

Hi @nuraidaA_Intel​ 

Thanks for the reply.

1) a) I am still not clear about the answer. As you said GT device maximum frequency is 400MHz, but is this the maximum frequency of the DDR memory or the DDR 3 memory controller?

b) If I am using the DDR controller at half rate, will the AFI clock frequency be half of 400 mhz?

I wanted to know the maximum frequency of the controller which deals with RTl side/ user code.

2) yes, I cannot cross the maximum frequency, but i meant to ask that, if 150 Mhz is maximum frequency for instance, then is it safe to use the maximum value or should consider something like 135 or 140 mhz. Will the functionality hamper if I use the maximum value of 150 mhz?

Thanks and Regards

Susmita

[NurAida_A_Intel]

Hi Susmita,

I am sorry if my earlier reply does not fully address your query. Please refer to my reply below:

1)

a) I am still not clear about the answer. As you said GT device maximum frequency is 400MHz, but is this the maximum frequency of the DDR memory or the DDR 3 memory controller?

[Aida]: It is the operating frequency of the memory interface.

b) If I am using the DDR controller at half rate, will the AFI clock frequency be half of 400 mhz?

I wanted to know the maximum frequency of the controller which deals with RTl side/ user code.

[Aida]: Yes, you are right. If the DDR_CK is 400 MHz, then the AFI_CK will be 200 MHz at half rate.

2) yes, I cannot cross the maximum frequency, but i meant to ask that, if 150 Mhz is maximum frequency for instance, then is it safe to use the maximum value or should consider something like 135 or 140 mhz. Will the functionality hamper if I use the maximum value of 150 mhz?

[Aida]: This is really depend on your design. As long you can get clean timing, then I don't see any problem using lower/maximum frequency. From my experienced so far, I don't see any functionality effect when using maximum frequency.

Hope this helps.

Thanks

Regards,

Aida

[Sushmita]

Hi @nuraidaA_Intel​ ,

Yes, this answered my doubts. Thanks a lot.

[NurAida_A_Intel]

You are welcome 😊