is it really so difficult for customers to think about future growth ?!
Now seriously - bigger memory modules means as well slower memory. Most clients want as fast memory as they can get for their needs. IBM gives you the option to purchase your frames with spare memory for future activation and assumes that you want the fastest memory for your estimated maximum memory needs.
Limitations are per node module (you have up to 4) + per frame
● 4 GB to 48 GB of 667 MHz DDR2 + 192 GB of 667 MHz DDR2 total or
● 16 GB to 96 GB of 533 MHz DDR2 + 384 GB of 533 MHz DDR2 total
● 32 GB to 192 GB of 400 MHz DDR2 + 768 GB of 400 MHz DDR2
there are additional requirements how many node modules need to have the same configuration - as far as I recall, you need to keep them the same or same or one level bigger (which slows down ALL memory)
Hope that helps
regards
zxmaus