[ECOS] i386 Memory Size Problem

kevin_lemay@agilent.com kevin_lemay@agilent.com
Tue Nov 25 16:30:00 GMT 2003


I found some sample code that makes the calls that I need.

Are there any examples of storing to the c/C++ variables that would help me to do the port?


-----Original Message-----
From: nickg@miso.calivar.com [mailto:nickg@miso.calivar.com]On Behalf Of
Nick Garnett
Sent: Tuesday, November 25, 2003 2:58 AM
To: LEMAY,KEVIN (A-Roseville,ex1)
Cc: ecos-discuss@sources.redhat.com
Subject: Re: [ECOS] i386 Memory Size Problem

kevin_lemay@agilent.com writes:

> There appears to be an issue with the pcmb_misc.c file where it determines to actual amount of extended memory available.
> It is reading bytes 0x17 and 0x18 from the CMOS which limits the RAM size to 64MB.
> I was trying to find the proper way to find out the memory size, and found the following on the web.
> Use BIOS calls: 
> INT 15h AX=E820h (32-bit CPU only). If this fails... 
> ...use INT 15h AX=E801h. If this fails... 
> ...use INT 15h AH=88h. 
> Read the extended memory size from CMOS only if all of the BIOS calls listed above fail. 
> How do I do this with eCos?
> I have a large application that I am porting that allocates lots of ram. I need more than 64MB.

You would need to put this code into the real mode startup code in
pcmb.inc or platform.inc. There's already calls to INT 15h AX=0x88 and
INT 12h there which just push the results, but then does nothing with
them -- I think this must be obsolete code. So the right thing to do is
probably to pull the pushed values after the switch to protected mode
and store them in cyg_hal_pcmb_memsize_base and
cyg_hal_pcmb_memsize_extended. Then just disable the options that
control the code in hal_pcmb_init().

Nick Garnett                    eCos Kernel Architect
http://www.ecoscentric.com      The eCos and RedBoot experts

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