DIMM Capacity Intermixing

[frederick hannah]

I have an rp7400 with 24GB of memory @ 1GB per chip (3 full carriers). I want to increase the memory capacity by adding more chips, but they are only 512MB per DIMM. Would adding the diffent "sized" DIMMs cause performance issues
or are they special instructions when mixing DIMMs of different capacities? The server is HPUX 11.11.

[Patrick Wallek]

When adding RAM to a server, the rule is to have the highest capacity DIMMs in the lowest numbered slots.

[Torsten.]

You can "mix" them by following special rules.

Example:

2x 1GB on ext 0
2x 1GB on ext 1
2x 1GB on ext 2
...
(until all 1GB are installed)
...
2x 512MB on ext 0
...
(until all are installed)

[frederick hannah]

The 1GB chips have occupied three extenders. I have room for only one extender which would have nothing but 512MB chips. Is such a configuration doable?

[Patrick Wallek]

You would need to migrate some of the 1GB Dimms to the 4th memory extender.

Essentially,

1 GB in ext0
1 GB in ext1
1 GB in ext2
1 GB in ext3

Do this until all your 1 GB DIMMs are used, then start with the 512 MB DIMMs.

512 MB in ext0
512 MB in ext1
512 MB in ext2
512 MB in ext3

Until all of your 512 MB are used.

[Torsten.]

Exactly.

No gaps! If you cannot equip all extenders with the same amount of similar dimms, just continue with the smaller size.

[Patrick Wallek]

OK, if you want to add 512MB DIMMs so that you have ALL memory slots filled in 4 carriers (upgrading from 1 GB DIMMs in 3 carriers) you would have:

1 GB DIMM in slot 0a/b - ext0
1 GB DIMM in slot 0a/b - ext1
1 GB DIMM in slot 0a/b - ext2
1 GB DIMM in slot 0a/b - ext3
1 GB DIMM in slot 1a/b - ext0
1 GB DIMM in slot 1a/b - ext1
1 GB DIMM in slot 1a/b - ext2
1 GB DIMM in slot 1a/b - ext3
1 GB DIMM in slot 2a/b - ext0
1 GB DIMM in slot 2a/b - ext1
1 GB DIMM in slot 2a/b - ext2
1 GB DIMM in slot 2a/b - ext3
512 MB DIMM in slot 3a/b - ext0
512 MB DIMM in slot 3a/b - ext1
512 MB DIMM in slot 3a/b - ext2
512 MB DIMM in slot 3a/b - ext3
512 MB DIMM in slot 4a/b - ext0
512 MB DIMM in slot 4a/b - ext1
512 MB DIMM in slot 4a/b - ext2
512 MB DIMM in slot 4a/b - ext3

So you now have a total of 32 DIMMs over 4 memory carriers.

[frederick hannah]

Thanks for the help. I am golden now.