A question about fitting resource usage summary

[Altera_Forum]

I have synthesis an Opencore to FPGA DE0 board, and I see the fitting resource usage summary in the compilation report which shows as below 

Total logic elements 2,039 / 15,408 ( 13 % ) Combinational with no register 1343 register only 35  Combinational with a register 661   Logic element usage by number of LUT inputs  -- 4 input functions 1279 -- 3 input functions 478 -- <=2 input functions 247 register only 35   Logic elements by mode   normal mode 1824  arithmetic mode 180 But when I reduced a JNE instrucion from the opencore ,and synthesis again, it shows Total logic elements 2,044 / 15,408 ( 13 % ) Combinational with no register 1348 register only 37  Combinational with a register 659   Logic element usage by number of LUT inputs  -- 4 input functions 1281 -- 3 input functions 482 -- <=2 input functions 244 register only 37   Logic elements by mode   normal mode 1827  arithmetic mode 180 It seems the logical elements it used increased? Why? Another question is in theory, when I reduced the instructions, the power consumption of the FPGA core should reduced, right? And is there any theory can explain the change of power consumption from this usage report? Thank you very much

[Altera_Forum]

What exactly do you call an "Opencore" and a "JNE instruction"?

[Altera_Forum]

Thank you for reply. the opencore is open MSP430 core, then I reduced the JNE instruction from the openMSP430 core, and synthesis it again

[Altera_Forum]

I'm not familiar with the core, but having written a microprocessor core (the Open8 uRISC), I can tell you that it isn't uncommon to see the compiler do surprising things in the face of "optimization" 

 I've written fairly simple address decoders in two styles. For some modules, I get lower usage with one style and not the other; and yet for other modules the reverse is true.  I am assuming from the mnemonic that JNE is Jump if Not Equal. I would imagine the ALU already creates the logic for equality testing, and the JNE instruction simply examines the status of the flag (probably the Z flag). This would explain the almost infinitesimal change in resource usage. The fact that it slightly increased may also come down to resource sharing that has changed as well.

[Altera_Forum]

Thank you!

[Altera_Forum]

Hi Jshmalet 

 Thanks very much for Open8_urisc core in opencores.org. 1. I find all the individual files including CPU; ALU,GPIO, CLK_DETECT etc but I don't find a top level VHDL file that binds it together. 2. Because it is written in VHDL'93 syntax and I am using ISE 10.1 (may be that uses VHDL 87) which uses different component declaration in o8_ram_1K which I tried to change by declaring a separate component (ram_1K_core) and a call to the component as in old style VHDL but it still din't like it complaining generic Address is not given value....  If you can please provide the top level file or any instructions that how can i put them together; I would really appreciate and if it can be a quick response that would be a real bonus..... Also any help in sorting the U_RAM and U_ROM_CORE(o8_ram_1K).... Looking forward to your help

[Altera_Forum]

It would appear ram_1k_core is missing from the repo.  

You will have to contact the author to find the missing files.  This is '93 syntax for direct instantiation. ISE should support it. But the core is missing, hence why it wont compile.

[Altera_Forum]

Thanks Tricky; The email address of the authors donot work.....Jshmalet is the author and hence I am trying to approach him. Also the top level module is missing

[Altera_Forum]

--- Quote Start ---  Thanks Tricky; The email address of the authors donot work.....Jshmalet is the author and hence I am trying to approach him. Also the top level module is missing  --- Quote End ---    Generally I never trust anything from OpenCores. I have found stuff to lack documentation, have poor coding styles and as you have found, missing modules. If you need support you are reliant on the original author, who may not have worked on it for a long time, or not be interested.  Generally, use at your own peril.

[Altera_Forum]

Yes, I understand. Cheers Tricky. I don't understand why the contact email addresses are not the right ones. Emails get bounced

[Altera_Forum]

The most recent files seem to be from nearly 2 years ago 

People'e email addresses change, people move on... showing just how untrustworthy opencores can be.