UPM works for 16MB PC SDRAM but fails for 32MB memory

laurent.mohin at acterna.com laurent.mohin at acterna.com
Fri Mar 29 18:53:00 EST 2002


I don't know the exact organisation of your SDRAMs, but you probably have a
problem with the MPC addresses you use to make the bank selection.
I guess you use two 16 bits devices of 8M to reach the 16MB size. With the
organisation you described, you use an address size of 21 bits (MPC A29-A9). So
you can use  MPC A8 and A7 for bank select.
But, if you plan to extend your SDRAM size to 32 MB (I guess you will use two 16
M devices), you have to use MPC A7 and A6 for bank select.

Hope it helps,


weiwu <weiwu at isdn.iscas.ac.cn> on 29/03/2002 02:38:19

To:   "linuxppc-embedded at lists.linuxppc.org"
      <linuxppc-embedded at lists.linuxppc.org>
Subject:  UPM works for 16MB PC SDRAM but fails for 32MB memory

I have bootrom code (ppcboot) for which I have UPM values with which I
can access the 16MB PC SDRAM okay but for 32MB memory
my bootrom fails to execute out of RAM.

software: Now I have modifyed the AMA and MAMR registers,but it still not work!

My board uses two HY57V281620A SDRAMS and it's configuration is 4 Banks x 2M x
16bits, 12 rows and 9 column.

A29 A0
A28 A1
A27 A2
A26 A3
A25 A4
A24 A5
A23 A6
A22 A7
A21 A8
A20 A9
GPL_A0 A10
A18 A11

A7 BA0
A8 BA1

What do I have to do get 32MB memory going?

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