[U-Boot-Users] I-cache and D-cache size problem on MPC859

Wolfgang Denk wd at denx.de
Mon Nov 14 14:33:15 CET 2005

In message <69DF49BE936F4441980EC1D59F0ADC2F010ADC04 at aqlby02a.siemens.it> you wrote:
> Now I have the U-Boot for MPC859, but I am not sure this line is correct
> U-Boot 1.1.3 (Nov 11 2005 - 16:38:24)
> CPU:   MPC859TxxZPnnA at 133 MHz: 16 kB I-Cache 8 kB D-Cache FEC present

Looks good to me.
> As far as I know, the I-Cache and the D-Cache of the MPC859 is 4 kB, as
> defined in the MPC866UM Appendix F.

Well, if you follow the Parametrics sheets on the freescale pages the
size is not 4 KiB (= 4096 Bytes), but 4000 Bytes instead. Looks bogus
to me.

> We think that the MPC859 probably has phisically the same cache size as the
> MPC866, but only 4 kB must be used.

U-Boot  uses  the  functions  checkicache()  and  checkdcache()  [see
"cpu/mpc8xx/cpu.c"]  to  measure  the  size of the L1 instruction and
data cache.

> Anyway, my question is, must I worry about the data printed on the screen or
> can I leave as they are?

I don't see how you could change the sizes.

> I mean, are these information used in other part of the U-Boot or the
> Kernel?

They are just informational messages.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Q: What do you get when you cross an ethernet with an income statement?
A: A local area networth.

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