Sun Ultra 5 / Ultra 10 RAM (memory upgrade notes)

The memory supported by Sun Ultra 5 / Ultra 10 is EDO DRAM, but there are some limitations...

Specifications:

1. Voltage is 3.3 V.
2. Form factor is 168-pin DIMM.
3. RAM is ECC-enabled.
4. RAM is buffered.
5. Access latency is 50 ns or 60 ns (lesser means quicker, therefore better peformance).
6. Refresh addressing size is 8K rows.

Quirks:

• RAM must be installed in pairs of identical size, so there can be only 2 or 4 DIMMs in the system; 4 identical modules result in best performance.
• When different speed (50 ns and 60 ns) DIMMs are mixed, the resulting memory speed is the worst one (60 ns), therefore it's not preferable to mix them.
• OBP version >=3.25v3 and CPU speed >=360 MHz is needed to use 50 ns memory (particularly, made by Micron Technology). It's better to update your OBP firmware to the latest version (OpenBoot 3.31, Sun/Oracle patch-ID# 106121-18) before memory upgrade.
• Do not use 16 MiB modules (they use 10-bit column addressing), as they cannot be mixed with any others (which use 11-bit column addressing). Therefore, you can safely use only 32, 64, 128 and 256 MiB DIMMs.
• Ordinary 256 MiB memory modules are not supported in Ultra 5 because of their size (you can try to use some "low-profile" 256 MiB DIMMs which have reduced height; alternatively, you can try to fit the box casing of Ultra 5 for your needs).
• Maximum memory module size for Ultra 10 is 256 MiB (the height of the DIMM doesn't matter there).
  Thus, the possible maximum of total RAM size in Sun Ultra 5 / 10 is 1 GiB (1024 MiB).

Be careful when buying memory modules; it's not necessary to choose only Sun-branded ones, but you should make sure it is a 8K refresh addressing EDO DRAM. Please read memory module & chip datasheets and check part numbers in advance, if you can. If you install "4K refresh" memory, it will seem to work, but the system will be able to use only a half of it (e. g., if you installed 4 x 256 MiB DIMMs, the system would show there's only 512 MiB of RAM available instead of 1 GiB).
For example, if you buy Micron Technology memory, you should probably choose MT*LD*72FG-* models ("F" is for 8K refresh). E. g.: MT36LD3272FG-5 X is a proper memory (256 MiB, EDO, 50 ns, 8K refresh) and MT36LD3272G-5 X is not (256 MiB, EDO, 50 ns, but 4K refresh).

Tested Sun-branded modules (to be updated)

Sun P/N	Module specs	Module manufacturer	Module model	Chip manufacturer	Chip model
370-3799-01	256 MiB, 50 ns	Samsung	KMM372F3280CS1-5	Samsung	KM44V16004CS-5
370-3799-02M	256 MiB, 50 ns	Micron	MT36LD3272FG-5 X	Micron	MT4LC16M4G3DJ-5 F

References:

1. Ultra 10 memory issue - Nekochan Net
2. Sun Ultra 10 RAM question(s) - Ars Technica OpenForum
3. Memory - Ultra 5 / Ultra 10 (A21 / A22) - Sun System Handbook
4. Micron datasheets ("MT9LD(T)872(F)X, MT18LD(T)1672(F)(D)X, MT36LD(T)3272(C)(F)X - 8, 16, 32 Meg x 72 Buffered DRAM DIMMs - Micron DRAM module datasheet" etc.)
5. Samsung datasheets (misc.)

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Last updated: 2017-01-17