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Old 1st March 2017
beiroot beiroot is offline
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Default OpenBSD - i386 vs amd64 - RAM

Hi,
I've a question I couldn't find the answer to googling.
When you have equal or more of 4GB RAM you need to install amd64?
I know it's true for the older versions of OpenBSD, but is it also true for 6.0?

What are the main reasons for this? I mean the technical answer - what are the architectural differences between those two architectures.

Thanks!
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Old 1st March 2017
e1-531g e1-531g is offline
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You don't need amd64, but your usable memory space would be limited to 4GB.
amd64 has 64-bit registers for addressing memory.
i386 has 32-bit registers for addressing memory.

2^32 [bytes] = 4294967296 [bytes] = 4 [GB]
2^64 [bytes] =(2^32)^2 [bytes] = 4294967296 * 4294967296 [bytes] = 16 Exabytes

There is something called PAE, but process address space remains expressed by 32-bit pointers, so you still have 4GB limit for every process in system.
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Last edited by e1-531g; 2nd March 2017 at 08:21 AM.
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Old 2nd March 2017
beiroot beiroot is offline
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That's a great answer, thank you

But...
Is it 4GB or 3GB according to this thread (jggimi's posts)?
http://daemonforums.org/showthread.php?t=8892

AFAI understand:
- PAE (available since OpenBSD 5.0?) addresses virtual memory (per process) and not physical (overall memory) - do I understand this correctly?
- bigmem - what is it?
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Old 2nd March 2017
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jggimi jggimi is offline
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Install and discover.

I have both i386 and amd64 systems; however none of the i386 systems have more than 512 MB of RAM.
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Old 6th March 2017
beiroot beiroot is offline
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Now that's what I call japanese-style minimalistic
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Old 6th March 2017
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They are Alix systems from PC Engines.
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