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TCM and ARM1136

hongkongrr hongkongrr
Note: This was originally posted on 13th January 2009 at http://forums.arm.com

Hi,

I am trying to use DTCM to see if I can improve performance of my program on ARM1136.

I wrote a test program that just read/write TCM and read/write to RAM.  However anlayzing the timing of the test program there seemed to be no performance increase at all.

Therefore, I am suspecting that I am not enabling TCM correctly.  Could someone please help me confirm, I am really stuck here :)?
-> I arbitrarily just picked 0x80000000 to use, since I know that nothing else is addressed there.  Can I do this? Or do I need to have some specific HW knowledge here?
-> Next I enabled it to use 4K TCM by ORing my base address it with 0xd.
-> If I used the following code, will any load/store that I subsequently do to 0x80000000 be going to TCM or am I missing something? 
MCR p15, 0, r0, c9, c1, 0;r0 was filled with (0x80000000|0xd)
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  • 0 Arm Employee Badge
    Note: This was originally posted on 13th January 2009 at http://forums.arm.com

    The size field of this CP15 register is ignored on write; the available TCM on the I and on the D interface is defined at synthesis time. How much TCM does your device actually provide (reading the register will tell you how much TCM is available)?

    The second point would be to make sure that you put data in D TCM, not I TCM. Loads and stores to I-TCM are a cycle slower than loads and stores to D TCM.
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  • 0 Arm Employee Badge
    Note: This was originally posted on 13th January 2009 at http://forums.arm.com

    The size field of this CP15 register is ignored on write; the available TCM on the I and on the D interface is defined at synthesis time. How much TCM does your device actually provide (reading the register will tell you how much TCM is available)?

    The second point would be to make sure that you put data in D TCM, not I TCM. Loads and stores to I-TCM are a cycle slower than loads and stores to D TCM.
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