Re: What to do with slow Chip/ST RAM

[mlelstv%serpens.de@localhost (Michael van Elst)]

abs%absd.org@localhost ("David Brownlee") writes:

>So the simplest way to have some ordering would be to assign priorities to 
>each memory segment passed by the bootloader - does it pass it in fastest 
>first?

All bootloaders just copy the AmigaOS memory list in order and the
list is, usually, sorted by speed. There are some options to select
a memory region for loading the kernel.

>Are there specific ranges known to be slow/fast ram which would help to 
>adjust/merge the list?

For all but one common configuration you could specify ranges.

The exception being the original Commodore accelerator cards which
may have fast 32bit RAM mapped into the Zorro-II address ranges.
Such a system could have up to 4MB 32bit RAM, 4MB 16bit Zorro-II
RAM and 2MB Chip RAM.  Is this enough for todays NetBSD? :)

>> There is one caveat, you cannot easily distinguish non-Chip RAM
>> and Ranger memory. Both are presented as 'Fast RAM' and may
>> use the same address space, non-Chip RAM however should not
>> be used. The easiest solution is to forget about both by
>> filtering out any memory region between 0x00A00000 and 0x00FFFFFF.

>So would that memory be used by anything (devices etc), if not its a perfect 
>candidate to be exposed as altmem... What happens to such memory now?

By default the memory region that was used to load the kernel is
the only generic memory used. Ranger/non-Chip RAM is ignored (unless
used for the kernel), Z-II memory might be used for DMA bounce
buffers when necessary and Chip memory is used for whatever the
chipset needs.

There is a boot loader option to use all fast memory regions instead.

The memory region that was used to load the kernel is added first
with uvm_page_physload(). Then the other memory regions in the list
are added. I don't know how that order is used by the UVM system.

-- 
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."