Index: generic/tclIO.c
==================================================================
--- generic/tclIO.c
+++ generic/tclIO.c
@@ -8707,11 +8707,11 @@
 			ChannelTimerProc, chanPtr);
 	    }
 	}
     }
 
-    if (!statePtr->timer
+    if (0 && !statePtr->timer
 	    && mask & TCL_WRITABLE
 	    && GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
 	TclChannelPreserve((Tcl_Channel)chanPtr);
 	statePtr->timerChanPtr = chanPtr;
 	statePtr->timer = Tcl_CreateTimerHandler(SYNTHETIC_EVENT_TIME,
@@ -8756,11 +8756,11 @@
     if (chanPtr->typePtr == NULL) {
 	CleanupTimerHandler(statePtr);
     } else {
 	Tcl_Preserve(statePtr);
 	statePtr->timer = NULL;
-	if (statePtr->interestMask & TCL_WRITABLE
+	if (0 && statePtr->interestMask & TCL_WRITABLE
 		&& GotFlag(statePtr, CHANNEL_NONBLOCKING)
 		&& !GotFlag(statePtr, BG_FLUSH_SCHEDULED)) {
 	    /*
 	     * Restart the timer in case a channel handler reenters the event loop
 	     * before UpdateInterest gets called by Tcl_NotifyChannel.

Index: generic/tclIORChan.c
==================================================================
--- generic/tclIORChan.c
+++ generic/tclIORChan.c
@@ -680,10 +680,15 @@
      */
 
     chan = Tcl_CreateChannel(&tclRChannelType, TclGetString(rcId), rcPtr,
 	    mode);
     rcPtr->chan = chan;
+    if (Tcl_SetChannelOption(interp, chan, "-buffering", "none") != TCL_OK) {
+	Tcl_Close(interp, chan); /* Will also free rcPtr etc. */
+	return TCL_ERROR;
+    }
+
     TclChannelPreserve(chan);
     chanPtr = (Channel *) chan;
 
     if ((methods & NULLABLE_METHODS) != NULLABLE_METHODS) {
 	/*

Index: tests/io.test
==================================================================
--- tests/io.test
+++ tests/io.test
@@ -6235,11 +6235,11 @@
 } -result {initial foo eof}
 
 close $f
 
 test io-44.6 {FileEventProc procedure: write-only non-blocking channel} -setup {
-} -constraints {stdio fileevent openpipe} -body {
+} -constraints {stdio fileevent} -body {
 
     namespace eval refchan {
 	namespace ensemble create
 	namespace export *
 

Index: tests/ioCmd.test
==================================================================
--- tests/ioCmd.test
+++ tests/ioCmd.test
@@ -1393,20 +1393,20 @@
     set c [chan create {r w} foo]
     note [fconfigure $c]
     close $c
     rename foo {}
     set res
-} -result {{-blocking 1 -buffering full -buffersize 4096 -encoding * -eofchar {} -profile * -translation {auto *}}}
+} -result {{-blocking 1 -buffering * -buffersize 4096 -encoding * -eofchar {} -profile * -translation {auto *}}}
 test iocmd-25.2 {chan configure, cgetall, no options} -match glob -body {
     set res {}
     proc foo args {oninit cget cgetall; onfinal; track; return ""}
     set c [chan create {r w} foo]
     note [fconfigure $c]
     close $c
     rename foo {}
     set res
-} -result {{cgetall rc*} {-blocking 1 -buffering full -buffersize 4096 -encoding * -eofchar {} -profile * -translation {auto *}}}
+} -result {{cgetall rc*} {-blocking 1 -buffering * -buffersize 4096 -encoding * -eofchar {} -profile * -translation {auto *}}}
 test iocmd-25.3 {chan configure, cgetall, regular result} -match glob -body {
     set res {}
     proc foo args {
 	oninit cget cgetall; onfinal; track
 	return {-bar foo -snarf x}
@@ -1414,11 +1414,11 @@
     set c [chan create {r w} foo]
     note [fconfigure $c]
     close $c
     rename foo {}
     set res
-} -result {{cgetall rc*} {-blocking 1 -buffering full -buffersize 4096 -encoding * -eofchar {} -profile * -translation {auto *} -bar foo -snarf x}}
+} -result {{cgetall rc*} {-blocking 1 -buffering * -buffersize 4096 -encoding * -eofchar {} -profile * -translation {auto *} -bar foo -snarf x}}
 test iocmd-25.4 {chan configure, cgetall, bad result, list of uneven length} -match glob -body {
     set res {}
     proc foo {args} {
 	oninit cget cgetall; onfinal; track
 	return "-bar"
@@ -2935,11 +2935,11 @@
 	notes
     } c]
     rename foo {}
     set res
 } -constraints {testchannel thread} \
-    -result {{-blocking 1 -buffering full -buffersize 4096 -encoding * -eofchar {} * -translation {auto *}}}
+    -result {{-blocking 1 -buffering * -buffersize 4096 -encoding * -eofchar {} * -translation {auto *}}}
 test iocmd.tf-25.2 {chan configure, cgetall, no options} -match glob -body {
     set res {}
     proc foo {args} {oninit cget cgetall; onfinal; track; return ""}
     set c [chan create {r w} foo]
     notes [inthread $c {
@@ -2948,11 +2948,11 @@
 	notes
     } c]
     rename foo {}
     set res
 } -constraints {testchannel thread} \
-    -result {{cgetall rc*} {-blocking 1 -buffering full -buffersize 4096 -encoding * -eofchar {} * -translation {auto *}}}
+    -result {{cgetall rc*} {-blocking 1 -buffering * -buffersize 4096 -encoding * -eofchar {} * -translation {auto *}}}
 test iocmd.tf-25.3 {chan configure, cgetall, regular result} -match glob -body {
     set res {}
     proc foo {args} {
 	oninit cget cgetall; onfinal; track
 	return "-bar foo -snarf x"
@@ -2964,11 +2964,11 @@
 	notes
     } c]
     rename foo {}
     set res
 } -constraints {testchannel thread} \
-    -result {{cgetall rc*} {-blocking 1 -buffering full -buffersize 4096 -encoding * -eofchar {} * -translation {auto *} -bar foo -snarf x}}
+    -result {{cgetall rc*} {-blocking 1 -buffering * -buffersize 4096 -encoding * -eofchar {} * -translation {auto *} -bar foo -snarf x}}
 test iocmd.tf-25.4 {chan configure, cgetall, bad result, list of uneven length} -match glob -body {
     set res {}
     proc foo {args} {
 	oninit cget cgetall; onfinal; track
 	return "-bar"