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Date: Fri, 22 Dec 2000 21:33:58 +0200
From: Petri Kaukasoina <kaukasoi@elektroni.ee.tut.fi>
To: linux-kernel@vger.kernel.org
Subject: Re: Linux 2.2.19pre3
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In-Reply-To: <E149GRm-0003sX-00@the-village.bc.nu>; from alan@lxorguk.ukuu.org.uk on Fri, Dec 22, 2000 at 12:52:32AM +0000
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On Fri, Dec 22, 2000 at 12:52:32AM +0000, Alan Cox wrote:
> 
> 2.2.19pre3
> o	Fix e820 handling				(Andrea Arcangeli)


arch/i386/kernel/setup.c:

                /* compare results from other methods and take the greater */
                if (ALT_MEM_K < EXT_MEM_K) {
                        mem_size = EXT_MEM_K;
                        who = "BIOS-88";
                } else {
                        mem_size = ALT_MEM_K;
                        who = "BIOS-e801";
                }
 
                e820.nr_map = 0;
-               add_memory_region(0, LOWMEMSIZE(), E820_RAM);
-               add_memory_region(HIGH_MEMORY, mem_size << 10, E820_RAM);
+               add_memory_region(0, i386_endbase, E820_RAM);
+               add_memory_region(HIGH_MEMORY, (mem_size << 10)-HIGH_MEMORY,
+                                E820_RAM);

I think in case of BIOS-88 it now sees 1 Meg less than should. int 15, ah=88
gives the amount of extended memory above 1 Meg and it gets copied to
EXT_MEM_K. So HIGH_MEMORY should not be subtracted from it. (On the other
hand in case of BIOS-e801 ALT_MEM_K includes lower memory. I guess the
direct comparison of memory sizes ALT_MEM_K and EXT_MEM_K is not ok.)

linux-2.2.19pre3 on my 486 with 49152 k of RAM:

BIOS-provided physical RAM map:
 BIOS-88: 000a0000 @ 00000000 (usable)
 BIOS-88: 02e00000 @ 00100000 (usable)
Memory: 46128k/48128k available

linux-2.2.18 or linux-2.2.19pre2 :

Memory: 47144k/49152k available
-
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