RAM for digital server 5300

[Simon Tierney]

Thanks for replying on this elementary hardware question Jay, I think I'll
risk trying the 512's because W. Bohrer has got them working and I just want
to beef up the RAM, not max out of the 4Gb limit.

Thanks,

Simon

----- Original Message ----- 
From: "Jay Estabrook" <jay.estabrook at hp.com>
To: "Linux on Alpha processors" <axp-list at redhat.com>
Sent: Wednesday, April 25, 2007 9:14 PM
Subject: Re: RAM for digital server 5300


Simon Tierney wrote:
> I have one of these machines which has cards to take PC100 ECC SDRAM
> modules, 1 card for each CPU.
>
> The Service and User manuals require replacement RAM  modules of 128 Mb
and
> 256 Mb (in pairs), but larger modules (512Mb) have become available since
> these manuals were written.
>
> Has anyone any experience adding these larger modules?  Will the system be
> able to address them, or should I stick to 256 modules?

I've no experience trying those 512MB DIMMs, but the docs do say that
the memory limit is 4GB done by 8 pairs of 256MB DIMMs, so I really
would NOT recommend trying anything larger. From the docs:

"The rules for addressing memory are as follows:

    * A memory pair consists of 2 DIMMs of the same size.
    * Memory pairs in riser cards may be of different sizes.
    * The memory pair in slot 0 must be the largest of all memory
      pairs. Other memory pairs may be as large but none may be
      larger.
    * The physical starting address of each memory pair is N times 512MB
      (2000000) where N is the slot number on the riser card.
    * Memory addresses are contiguous within each module pair.
    * If memory pairs do not completely fill the 512MB space provided,
      memory “holes” occur in the physical address space.
    * Software creates contiguous virtual memory even though physical
      memory may not be contiguous."

So, it's really a hardware limitation in the way that memory DIMM pairs
are mapped into the physical address space, that tops out at 4MB on the
5300.

Sorry.

--Jay++

-- 
Jay A Estabrook                            HPTC - XC I & B
Hewlett-Packard Company - ZKO1-3/D-B.8     (603) 884-0301
110 Spit Brook Road, Nashua NH 03062       Jay.Estabrook at hp.com

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