From eabee261d32f07e280856a58a619307e384929c9 Mon Sep 17 00:00:00 2001
From: Tom Collins <tom.collins@digi.com>
Date: Thu, 25 Mar 2021 15:22:05 -0700
Subject: [PATCH 1/2] BIOS: don't modify MTCR if spectrum spreading disabled

There may be instances where we want a non-zero MTCR even if the
spectrum spreader is disabled.  By leaving it unmodified, it might still
be zero from the default startup value, or set non-zero elsewhere.
---
 Lib/BIOSLIB/CPUPARAM.LIB | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/Lib/BIOSLIB/CPUPARAM.LIB b/Lib/BIOSLIB/CPUPARAM.LIB
index 92e5e2c..e5f77c1 100644
--- a/Lib/BIOSLIB/CPUPARAM.LIB
+++ b/Lib/BIOSLIB/CPUPARAM.LIB
@@ -162,14 +162,7 @@ END DESCRIPTION ***************************************************************/
 #asm xmem nodebug
 _enableClockModulation::
 	bool	hl
-#if _CPU_ID_ < R2000_R3
-	ld		l, h
-	lret
-#elif ENABLE_SPREADER == 0	// spreader disabled
-	xor	a
-	ld		(MTCRShadow), a
-;	ioi	ld (MTCR), a		// normal /OE0 and /OE1 timing
-	IOWRITE_A(MTCR)
+#if _CPU_ID_ < R2000_R3 || ENABLE_SPREADER == 0
 	ld		l, h
 	lret
 #else

From b529bc8339571b9900ed69ccc4d9678e9adb3cbe Mon Sep 17 00:00:00 2001
From: Tom Collins <tom.collins@digi.com>
Date: Tue, 6 Apr 2021 13:25:12 -0700
Subject: [PATCH 2/2] BIOS: enable early /OE before clock doubler

This increases the /OE timing margin for 29MHz products with 55ns
flash memory for the brief moment before _enableClockModulation()
enables it, and ensures it's still enabled if the spectrum spreader is
disabled.
---
 Lib/BIOSLIB/StdBios.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/Lib/BIOSLIB/StdBios.c b/Lib/BIOSLIB/StdBios.c
index 5a4d466..4d2da9c 100644
--- a/Lib/BIOSLIB/StdBios.c
+++ b/Lib/BIOSLIB/StdBios.c
@@ -2452,12 +2452,19 @@ _more_inits02::
    ld    hl, GCSRShadow
    ld    (hl), a
 
-   lcall   _getDoublerSetting
-
-   ld      a, l
+   lcall   _getDoublerSetting   ; get doubler setting value into L (h always 0)
+   ld      a, L
+   or      a                    ; update the Zero flag
+   jr      z, .notDoubled
+
+   ld      a, 0x0C              ; value to set both /OE0 and /OE1 early output
+   ioi ld  (MTCR), a            ; first, update /OE0, /OE1 early output enable
+   ld      (MTCRShadow), a
+
+.notDoubled:
+   ld      a, L                 ; recover the doubler setting value
+   ioi ld  (GCDR), a            ; next, update clock doubler setting
    ld      (GCDRShadow), a
-   ioi   ld (GCDR), a      ; set clock doubler now
-
 
 #if _CPU_ID_ >= R2000_R3
    lcall   _enableClockModulation	; enables spreader