The DSP runs at extremely low speed, Why?

Coskun AYYILDIZ

Other Parts Discussed in Thread: DM3730

Hi everyone,

I am using DM3730 (having C64X+ in it) to run a simple for loop. What I see is that the DSP is running at very very low speed.

I am using Blackhawk USB560 BP emulator and EVAL version of CCSv4 (without BIOS). I run the following piece of code.

#include <stdio.h>

#include <time.h>

void main()

{

int i, s1, s2, t;

s1 = time(NULL);

for(i = 0; i < 100000000; i++)

{}

s2 = time(NULL);

t = s2 - s1;

printf("t = %d s", t);

}

After executing this code, I see t = 14 s. It means that the DSP is running at 7 MHz. I would expect it to be 800 MHz.

What causes the DSP to run this much slowly? Is it because I am using the EVAL version of CCS? Can anyone suggest me how I can fix it?

Besides, is there a way to learn the exact clock frequency of the DSP.

Best Regards,

Coskun

over 15 years ago

0 ToddMullanix over 15 years ago

TI__Guru* 96960 points

Hi Coskun,

This is not a valid test to determine the processor speed. I'm assuming you got 7 MHz from 100,000,000/14s. The "for" loop you have is not going to take 100,000,000 cycles. Depending on your compiler options it could take a lot more (e.g. debug options) or almost none (e.g. optimization and the compiler sees you are doing nothing in the loop). The c64+ family has two 32-bit registers (TSCL and TSCH...where H is high and L is low). These registers maintain a 1-1 count of the cycles. To verify the CPU speed. Run the same test, but look at TSCL/TSCH at the start and end of the test. They should verify the frequency.

For example. If TSCL/H were zero at the beginning, after 14s, TSCH and TSCL should be approximately 0x00000002 and 0x9B927000 (800,000,000 * 14).

note: there are some rules with programically reading TSCL and TSCH (I think you have to read the L one first and then immediately read the H one). CCS handles this when look at the register view in CCS.

Todd

0 Coskun AYYILDIZ over 15 years ago in reply to ToddMullanix

Prodigy 90 points

Thanks for your reply Todd,

Now I read the TSCL and TSCH registers and see that the DSP is actually running at slow speed.

Now, I dont see 800,000,000 * 14 but I see much less than that value (about 1/10 of that value).

Do I need to configure the PLL registers to enable the DSP to run at max speed? I looked at the user manual but could not figure out how to set the register for this purpose.

Or, might there be any other thing that I should do?

Thanks again.

Best regards,

Coskun

0 Karl Wechsler over 15 years ago in reply to Coskun AYYILDIZ

TI__Mastermind 20805 points

Coskun --

Do you have a .gel file for that board? Usually the .gel file has a command and logic to program the PLL. This logic can be duplicated in C code and done on the target.

-Karl-

0 Brad Griffis over 15 years ago in reply to Karl Wechsler

TI__Guru*** 125430 points

In almost every scenario where performance is orders of magnitude less than expected, the root cause is cache/memory related. In this case I suspect you have code/data in external memory and do not have the proper cache configuration. Please see this article for more info:

http://processors.wiki.ti.com/index.php/Enabling_64x%2B_Cache

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The DSP runs at extremely low speed, Why?