What is Dedicated Logic Register(DLR) and fmax?

[Altera_Forum]

Hi everyone, 

I am choosing a proper Altera device for a matrix multiplication which needs to implement floating point. Megafuntion can help design that kind of multiplier in simple steps.  However I am not quite sure about the resource usage part in the tech documentation like Dedicated Logic Register(DLR) and fmax. I have googled such terms but received no useful information. I have to be very careful about that because I need 200 multipliers in a cyclone 3 devices but I am not sure whether it can handle this work. Does anyone here know about DLR or fmax? Thanks 

[Altera_Forum]

--- Quote Start ---  Hi everyone, I am choosing a proper Altera device for a matrix multiplication which needs to implement floating point. Megafuntion can help design that kind of multiplier in simple steps.  However I am not quite sure about the resource usage part in the tech documentation like Dedicated Logic Register(DLR) and fmax. I have googled such terms but received no useful information. I have to be very careful about that because I need 200 multipliers in a cyclone 3 devices but I am not sure whether it can handle this work. Does anyone here know about DLR or fmax? Thanks   --- Quote End ---    Hi,  DLR is the number of used registers. Fmax indicates the maximal frequency for the design, under worst case conditions ( lowest power, max temperature ...)

[Altera_Forum]

--- Quote Start ---  Hi,   DLR is the number of used registers. Fmax indicates the maximal frequency for the design, under worst case conditions ( lowest power, max temperature ...)  --- Quote End ---   Thanks for your replying. Yet I still have some questions: 1. in the doc of Megafuntion User Guide, it is said that the logic usage for a single precision floating point multiplier in Cylone 3 is 295 and also it has indicated that it need 221 Dedicated Logic Registers(DLR). Are these DLRs used included in the logic usage mentioned above? Why I ask this question is that the resource usage for each multiplier is really a concern in my project.   2. Does fmax indicate that frequency of the driving clock or that of the output signals? And that user guide also provides specific number for fmax, such as 209 for a single precision floating point multiplier yet without stating it unite. So I don't know whether it is in megaHz or gigaHz...   Thanks

[Altera_Forum]

--- Quote Start ---  Thanks for your replying. Yet I still have some questions: 1. in the doc of Megafuntion User Guide, it is said that the logic usage for a single precision floating point multiplier in Cylone 3 is 295 and also it has indicated that it need 221 Dedicated Logic Registers(DLR). Are these DLRs used included in the logic usage mentioned above? Why I ask this question is that the resource usage for each multiplier is really a concern in my project.   2. Does fmax indicate that frequency of the driving clock or that of the output signals? And that user guide also provides specific number for fmax, such as 209 for a single precision floating point multiplier yet without stating it unite. So I don't know whether it is in megaHz or gigaHz...   Thanks  --- Quote End ---    Hi,  I'm not sure, but I would assume that the registers are included in logic usage. Be aware that the default setting of the megafunction used "embedded multiplier" ( could be disabled ), means that you not only have to look to the registers or logic usage. When the multiplier is generated with logic elements only, you need a lot more FPGA resources.  I would recommand that you generate one example of your multiplier and look to the resource utilization after P&R.  Fmax is the speed at which your multiplier can run. Fmax is limited by the longest path between the registers.