Where can I find the "Touch Assembly Routine "?

Peter010

Hello everyone

When I was reading the TMS320C66x DSP Cache User Guide, on the page 72 it said that:

Exploiting miss pipelining can further reduce the cache miss stalls. The touch loop discussed in Section 3.2.2 is used to preallocate all arrays, in1, in2, w1, and w2, in L1D. Since all arrays are allocated contiguously in memory, one call of the touch routine is sufficient:

touch(in1, 4*N*sizeof(short));
r1 = dotprod(in1, w1, N);
r2 = dotprod(in2, w2, N);
r3 = dotprod(in1, w2, N);
r4 = dotprod(in2, w1, N);

In the Section 3.2.2, it gives an example for the touch assembly for the C64x DSP. So my question is at what place I may find or include the files that contains the "touch" function for C66x.

The user guide is in the attachment.

Thanks

Xining Yu

TMS320C66x DSP Cache.pdf

over 10 years ago

0 Raja over 10 years ago

TI__Guru* 81335 points

Hi Xining Yu,
My understanding is that, you can use the "touch assembly of C64x DSP" for C66x. I am checking with our experts for further help. Thank you for your patience.

0 ran35366 over 10 years ago in reply to Raja

TI__Genius 12805 points

Xining Yu

The touch function pre-read values into the cache, but of course it takes cycles to move the data into the cache.

To understand better the trade-offs when using the touch look at this posting. It is for C674X but the same is true for C66 as well

You can find the source code in the posting. C66 assembly is backward compatible with C674.

But remember that the C66 has pre-fetch registers that pre-load data from DDR by the hardware. Using the pre-fetch may make the complete program runs faster without the touch than with the touch.

My advice - benchmark the performances of your complete program in both cases with and without touch but enable pre-fetch.

pre-fetch is enabled as part of the MAR registers. See 4.3.7.1 of

http://www.ti.com/lit/ug/sprugw0c/sprugw0c.pdf

And the touch posting is in https://e2e.ti.com/support/dsp/omap_applications_processors/f/42/t/297080

Ran

0 Peter010 over 10 years ago in reply to ran35366

Genius 4165 points

Thanks for your replying.

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Where can I find the "Touch Assembly Routine "?