Replace my 256M (4M x 4 Banks x 16 bit) SDRAM Memory to 512M (8M x 4 Banks x 16 bit)

[diggdip]

Hi

I'm trying to replace my 256M (4M x 4 Banks x 16 bit) SDRAM Memory to 512M (8M x 4 Banks x 16 bit) SDRAM Memory (pin compatible).

I have 32 bit CPU (SDRAM interface runs at 133 MHz clock frequency) using higher and lower addresses bits, for 2 of such devices:
1. I think i can do it without any problems am i correct? What could be the limitations?
2. I also had problem to find the exact clock frequency devices. would a 143 MHz SDRAM work for such configuration? What could be the limitations?

Thanks!

 

[BradtheRad]

You should install the same speed, or faster, memory. Therefore the 143 MHz chips should be okay in your 133 MHz equipment.

 

[FvM]

Re: Can I use SDRAM 133Mhz with clock 100Mhz or belower?

256M and 512M SDRAM have different page sizes. Software changes might be required to handle it.

 

[diggdip]

Wouldn't it be considered as overclocking, won't it affect system stability?

 

[FvM]

Wouldn't it be considered as overclocking

I think you are talking about "under"clocking.

 

[diggdip]

I suppose you're right it is under-clocking.
So if i understand the issue correct if i'll use the 144 MHz rated SDRAM with 133 MHz SDRAM controller clock frequency,
the system simply will operate in 133 MHz clock frequency?

 

[alexan_e]

The RAM doesn't have a clock generator on board it works with the clock that the system feeds , if that is 133MHz then the RAM will work @133MHz

 

[diggdip]

How about using DDR or DDR2 instead of older SDRAM how would matter?