Index: support.4th
===================================================================
--- support.4th	(revision 242835)
+++ support.4th	(working copy)
@@ -201,6 +201,42 @@ create last_module_option sizeof module.next allot
 
 : getenv?  getenv -1 = if false else drop true then ;
 
+\ determine if a word appears in a string, case-insensitive
+: contains? ( addr1 len1 addr2 len2 -- 0 | -1 )
+	2 pick 0= if 2drop 2drop true exit then
+	dup 0= if 2drop 2drop false exit then
+	begin
+		begin
+			swap dup c@ dup 32 = over 9 = or
+			over 10 = or over 13 = or swap drop
+		while 1+ swap 1- repeat
+		swap 2 pick 1- over <
+	while
+		2over 2over drop over compare-insensitive 0= if
+			2 pick over = if 2drop 2drop true exit then
+			2 pick tuck - -rot + swap over c@ dup 32 =
+			over 9 = or over 10 = or over 13 = or
+			swap drop if 2drop 2drop true exit then
+		then begin
+			swap dup c@
+			dup 32 = over 9 = or over 10 = or over 13 = or
+			swap drop if false else true then 2 pick 0> and
+		while 1+ swap 1- repeat
+		swap
+	repeat
+	2drop 2drop false
+;
+
+: boot_serial? ( -- 0 | -1 )
+	s" console" getenv dup -1 <> if
+		s" comconsole" 2swap contains?
+	else drop false then
+	s" boot_serial" getenv dup -1 <> if
+		s" YES" compare-insensitive 0=
+	else drop false then
+	or ( true if either console contains comconsole or boot_serial=YES )
+;
+
 \ Private definitions
 
 vocabulary support-functions
Index: frames.4th
===================================================================
--- frames.4th	(revision 242835)
+++ frames.4th	(working copy)
@@ -12,6 +12,11 @@ variable rt_el
 variable rb_el
 variable fill
 
+\ ASCII frames (used when serial console is detected)
+ 45 constant ascii_dash
+124 constant ascii_pipe
+ 43 constant ascii_plus
+
 s" arch-pc98" environment? [if]
 	\ Single frames
 	149 constant sh_el
@@ -63,7 +68,17 @@ s" arch-pc98" environment? [if]
 	loop
 ;
 
+: f_ascii ( -- )	( -- )	\ set frames to ascii
+	ascii_dash h_el !
+	ascii_pipe v_el !
+	ascii_plus lt_el !
+	ascii_plus lb_el !
+	ascii_plus rt_el !
+	ascii_plus rb_el !
+;
+
 : f_single	( -- )	\ set frames to single
+	boot_serial? if f_ascii exit then
 	sh_el h_el !
 	sv_el v_el !
 	slt_el lt_el !
@@ -73,6 +88,7 @@ s" arch-pc98" environment? [if]
 ;
 
 : f_double	( -- )	\ set frames to double
+	boot_serial? if f_ascii exit then
 	dh_el h_el !
 	dv_el v_el !
 	dlt_el lt_el !