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Re: 32-bit MIPS with > 512mb mem

To: Ralf Baechle <>
Subject: Re: 32-bit MIPS with > 512mb mem
From: "Gleb O. Raiko" <>
Date: Thu, 17 Feb 2000 14:18:16 +0300
Organization: NIISI RAN
References: <>
Ralf Baechle wrote:
> Is anybody using 32-bit MIPS CPUs which have more than 512mb of memory or
> to be more exact have RAM that isn't accessible via the KSEG0 / KSEG1
> window?
> So far I haven't ever seen such a machine.  For 64-bit CPUs the right
> thing to do is easy - use a 64-bit kernel.  But for 32-bit CPUs the Intel
> highmem stuff in the memory managment now gives us a sane way to use
> the memory of such configuration with just a little bit of extra code.
> So if anybody wants support for such a configuration, please drop me a
> note.

Not exactly > 512 mb, but related things. On Baget and DECstations, if
memory serves correctly, there is IO space mapped on KSEG2. Now, Baget
uses kseg2_allocate_io for it, DECstation also has something similar. IO
space on Jazz and Co. are located in virtual address window too, can't
remember where. In princple, access to such IO spaces may be done by
using highmem.


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