From b5339d68dcd76af376286bb3ef4e5a9c32947aad Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Wed, 30 Sep 1992 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1992-09-30

---
 pc/mem.h |  1 +
 pc/mmu.c | 16 ++++++----------
 2 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/pc/mem.h b/pc/mem.h
index 1a8672e50ac9a5c1221b2c87a0f491bcbefebc68..a9e3a0dfefc4a10f49a9bb5edeb102c9c1c8d055 100644
--- a/pc/mem.h
+++ b/pc/mem.h
@@ -49,6 +49,7 @@
 #define	USTKTOP		(TSTKTOP-TSTKSIZ*BY2PG)	/* byte just beyond user stack */
 #define	USTKSIZE	(16*1024*1024 - TSTKSIZ*BY2PG)	/* size of user stack */
 #define ROMBIOS		(KZERO|0xF0000)
+#define	ISAMEMSIZE	(4*MB)			/* mem space reserved for ISA */
 
 #define	MACHSIZE	4096
 
diff --git a/pc/mmu.c b/pc/mmu.c
index f189bb48cac352aa77f9d93b53e363a5987f7771..a8679fff4921e3ab50ec62f12cf68e88274072b8 100644
--- a/pc/mmu.c
+++ b/pc/mmu.c
@@ -130,16 +130,12 @@ mmuinit(void)
 	ktoppg.va = (ulong)top;
 	ktoppg.pa = ktoppg.va & ~KZERO;
 
-	/*  map all memory to KZERO (plus 1 meg for PCMCIA window) */
-	npage = conf.topofmem/BY2PG;
-	if(conf.topofmem < 64*MB){
-		/* for ISA bus memory */
-		isamemalloc.addr = conf.topofmem;
-		isamemalloc.end = conf.topofmem + 2*MB;
-		if(isamemalloc.end > 64*MB)
-			isamemalloc.end = 64*MB;
-		npage += (isamemalloc.end - isamemalloc.addr)/BY2PG;
-	}
+	/*  map all memory to KZERO (add some address space for ISA memory) */
+	isamemalloc.addr = conf.topofmem;
+	isamemalloc.end = conf.topofmem + ISAMEMSIZE;
+	if(isamemalloc.end > 64*MB)
+		isamemalloc.end = 64*MB;	/* ISA can only access 64 meg */
+	npage = isamemalloc.end/BY2PG;
 	nbytes = PGROUND(npage*BY2WD);		/* words of page map */
 	nkpt = nbytes/BY2PG;			/* pages of page map */
 	kpt = xspanalloc(nbytes, BY2PG, 0);