Re: Re: Fwd: memory probing

[coly li]

alfred hitch:

Bios can provide us a memory map table, for it knows the initial address space 
layout, why it knows, because bios itself does the initial mapping for address 
space.

In a non-bios enviornment, we can't get the memory map table by calling bios 
service, so, we have to detect the size of memory by ourselves.

write and verify means: you read the content from location X, and change the 
value, then write back to location X; then re-read the content from X, if the 
value is what you write, the location X is valid; otherwise, maybe the location 
X is invalid.

as a trick, you need not verify the memory linearly, you can verify it in the 
power-of-two, only perform linearly dectecting after the prior detecting 
failed. 
                                 
　　　　　　　　coly li
address@hidden
　　　　　　　　　　2005-05-10


======= 2005-05-10 16:33:25 original messages：=======

>thanks,
>but what did u mean write and verify, 
>I thhot grub depends heavilly on bios calls for all this .. 
>
>Alfred
>
>On 5/10/05, coly li <address@hidden> wrote:
>> alfred hitch:
>> 
>> It's not so easy to get the proper answer. it depends on your hardware. for 
>> I'm not familiar with embedded enviornmnet, I can only give you some idea 
>> for x86 platform.
>> 
>> you should know your memory address space layouts. which range is for other 
>> peripheral, which range is for real memory. different range use difference 
>> detecting scheme. for the range of real memory, the simplest method is 
>> "write and verify".
>> 
>> but, for I'm not a embedded programmer, I can't give you more information 
>> for non-x86. FYI.
>> 
>> coly li
>> address@hidden
>> 2005-05-10
>> 
>> ======= 2005-05-10 14:36:51 original messages：=======
>> 
>> >---------- Forwarded message ----------
>> >From: alfred hitch <address@hidden>
>> >Date: May 10, 2005 2:13 AM
>> >Subject: Re: memory probing
>> >To: The development of GRUB 2 <address@hidden>
>> >
>> >
>> >Hi,
>> >
>> >thanks for your response,
>> >actually what I am looking for is that does grub and all use bios
>> >calls to find out the memory size ?
>> >on my system there is no bios, ixdp425 based plattform,
>> >then can I somehow probe amount of memory and not use a #define'ed one ?
>> >
>> >Cheers,
>> >Alfred
>> >
>> >On 5/10/05, coly li <address@hidden> wrote:
>> >> alfred hitch:
>> >>
>> >> hi! I guess what you want to know more is the initialization for linux 
>> >> kernel.
>> >> I know a guy who wirtes a perfect text named "i386 linux boot howto", you 
>> >> can find out this text on www.tldp.org.
>> >> also, I sugest you read the linux boot protocol, you can find this text 
>> >> in linux kenrel source code. maybe the name is boot.txt.
>> >>
>> >> good luck;-)
>> >>
>> >> coly li
>> >> address@hidden
>> >> 2005-05-10
>> >>
>> >> ======= 2005-05-10 12:08:54 original messages：=======
>> >>
>> >> >Hi All,
>> >> >
>> >> >I am trying to understand working of bootloaders and have a question
>> >> >(which might be very elementary perhaps).
>> >> >
>> >> >I wanted to understand how does bootloaders probe memory installed on
>> >> >system and thus pass the correct mem option across to linux kernel
>> >> >say.
>> >> >
>> >> >Can someone please explain if this is dependant on bios necessarilly,
>> >> >as I am looking for doing something similar on ixdp425 plattform.
>> >> >
>> >> >Can u please point me to some relavant doc / code ..
>> >> >
>> >> >Cheers,
>> >> >Alfred
>> >> >
>> >> >
>> >> >_______________________________________________
>> >> >Grub-devel mailing list
>> >> >address@hidden
>> >> >http://lists.gnu.org/mailman/listinfo/grub-devel
>> >>
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>> >>
>> >>
>> >> _______________________________________________
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>> >>
>> >>
>> >>
>> >
>> >
>> 
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>> 
>>

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