diff --git a/src/enqueue.cc b/src/enqueue.cc
index a1fca5edf3..100e05a52e 100644
--- a/src/enqueue.cc
+++ b/src/enqueue.cc
@@ -426,6 +426,26 @@ static ncclResult_t getAlgoInfo(struct ncclInfo* info, int collNetTypeSupport, i
   if (info->coll == ncclFuncAllToAllPivot) {
     int pivotA2ANumUniRings = comm->topo->pivotA2ANumBiRings * 2;
     info->nChannels = comm->nChannels / pivotA2ANumUniRings * pivotA2ANumUniRings;
+  } else if (comm->topo->nodes[GPU].nodes[0].gpu.gcn == 910 && comm->nChannels == 32 && comm->nRanks/comm->nNodes == 16 && info->nBytes >= 268435456
+    && ((comm->nNodes > 2 && info->nBytes <= 2147483648) || (comm->nNodes == 2 && info->nBytes <= 1073741824))) {
+    static int userTuneInput = -2;
+    if (userTuneInput == -2) {
+      const char *protoStr = getenv("NCCL_PROTO");
+      const char *algoStr = getenv("NCCL_ALGO");
+      if (!protoStr && !algoStr)
+        userTuneInput = 0;
+      else
+        userTuneInput = 1;
+    }
+    if (userTuneInput) {
+      // always respect user settings
+      info->nChannels = nc;
+    } else {
+      // use ring simple with reduced channels on gfx90a for specific data sizes
+      info->protocol = NCCL_PROTO_SIMPLE;
+      info->algorithm = NCCL_ALGO_RING;
+      info->nChannels = nc/2;
+    }
   } else {
     info->nChannels = nc;
   }
diff --git a/src/graph/tuning.cc b/src/graph/tuning.cc
index 6b1f3f31bf..201c40e7f7 100644
--- a/src/graph/tuning.cc
+++ b/src/graph/tuning.cc
@@ -63,11 +63,11 @@ static const float baseLat  [NCCL_NUM_ALGORITHMS][NCCL_NUM_PROTOCOLS] = { { 12.0
 // Tree/Simple is the latency a 256kB chunk, which is ~ base lat + 256k/12GB/s (+ 256k/12GB/s for the network).
 static float hwLat [3][NCCL_NUM_ALGORITHMS][NCCL_NUM_PROTOCOLS] =
 { /* NVLINK */
-  { /* Tree (LL/LL128/Simple)*/ { 1.5, 1.5, 4.5 }, /* Ring (LL/LL128/Simple)*/ { 1.5, 1.5, 4.5 }, /* CollNet (LL/LL128/Simple)*/ { 1.2, 1.2, 3.8 } },
+  { /* Tree (LL/LL128/Simple)*/ { 1.5, 1.5, 4.5 }, /* Ring (LL/LL128/Simple)*/ { 1.5, 1.5, 4.5 }, /* CollNet (LL/LL128/Simple)*/ { 1.5, 1.5, 4.5 } },
   /* PCI */
   { /* Tree (LL/LL128/Simple)*/ { 2.2, 2.2, 5.7 }, /* Ring (LL/LL128/Simple)*/ { 2.2, 2.2, 5.7 }, /* CollNet (LL/LL128/Simple)*/ { 2.2, 2.2, 5.7 } },
   /* NET */
-  { /* Tree (LL/LL128/Simple)*/ { 40.0, 40.0, 50.0 }, /* Ring (LL/LL128/Simple)*/ { 4.0, 4.0, 25.0 }, /* CollNet (LL/LL128/Simple)*/ { 9.8, 9.8, 19.5 } }
+  { /* Tree (LL/LL128/Simple)*/ { 33.0, 33.0, 15.8 }, /* Ring (LL/LL128/Simple)*/ { 5.1, 5.1, 68.8 }, /* CollNet (LL/LL128/Simple)*/ { 33.0, 33.0, 15.8 } }
 };
 
 // LL128 max BW per channel
@@ -134,10 +134,9 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
 
         // Various model refinements
 #if defined(__HIP_PLATFORM_HCC__) || defined(__HCC__) || defined(__HIPCC__)
-        if (a == NCCL_ALGO_RING && (p == NCCL_PROTO_LL || p == NCCL_PROTO_LL128)) busBw *= 0.05;
-        if (a == NCCL_ALGO_TREE && p == NCCL_PROTO_SIMPLE) (nNodes == 2) ? busBw *= 0.33 : busBw *= 0.11;
-        if (a == NCCL_ALGO_TREE && (p == NCCL_PROTO_LL || p == NCCL_PROTO_LL128)) busBw *= 0.04;
-        if (gcn == 910 && a == NCCL_ALGO_TREE && p == NCCL_PROTO_SIMPLE && nNodes == 2 && nRanks == 32) busBw *= 3.61;
+        if (a == NCCL_ALGO_RING && (p == NCCL_PROTO_LL || p == NCCL_PROTO_LL128)) busBw *= 0.20;
+        if (a == NCCL_ALGO_TREE && p == NCCL_PROTO_SIMPLE) (nNodes == 2) ? busBw *= 0.99 : busBw *= 0.42;
+        if (a == NCCL_ALGO_TREE && (p == NCCL_PROTO_LL || p == NCCL_PROTO_LL128)) busBw *= 0.15;
         if (gcn == 910 && a == NCCL_ALGO_TREE && p == NCCL_PROTO_SIMPLE && nNodes == 2 && nRanks == 16) busBw *= 6.5;
 #else
         if (compCap80) busBw = std::min(busBw, 235.0f);
@@ -282,18 +281,19 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
 
 // Trees are not perfectly sticking to the model for medium sizes. Applying a static correction
 // factor is not ideal but works quite well. Powers of two, 64 B to 128MB.
-static float treeCorrectionFactor[NCCL_NUM_PROTOCOLS][25] = {
-  { 0.7, 0.7, 0.7, 0.6, 0.6, 0.3, 0.9, 0.5, 0.5, 0.6, 0.5, 0.5, 0.8, 0.9, 0.8, 0.8, 0.8, 0.8, 0.8, 0.9, 0.9, 1.0, 1.0, 1.0, 1.0, },
-  { 0.7, 0.7, 0.7, 0.6, 0.6, 0.3, 0.9, 0.5, 0.5, 0.6, 0.5, 0.5, 0.8, 0.9, 0.8, 0.8, 0.8, 0.8, 0.8, 0.9, 0.9, 1.0, 1.0, 1.0, 1.0, },
-  { 0.4, 0.4, 0.3, 0.3, 0.2, 0.5, 0.5, 0.7, 0.2, 0.2, 0.3, 0.6, 0.7, 1.0, 1.3, 1.0, 1.2, 1.2, 1.1, 1.1, 1.2, 1.2, 1.5, 1.7, 2.4, },
+static float treeCorrectionFactor[NCCL_NUM_PROTOCOLS][27] = {
+  { 0.5, 0.4, 0.7, 0.6, 1.0, 1.0, 0.5, 0.4, 0.1, 0.5, 0.4, 0.6, 1.0, 1.0, 1.0, 1.0, 1.0, 0.8, 0.6, 0.5, 0.4, 0.4, 0.3, 0.2, 0.1, 0.1, 0.1, },
+  { 0.5, 0.4, 0.7, 0.6, 1.0, 1.0, 0.5, 0.4, 0.1, 0.5, 0.4, 0.6, 1.0, 1.0, 1.0, 1.0, 1.0, 0.8, 0.6, 0.5, 0.4, 0.4, 0.3, 0.2, 0.1, 0.1, 0.1, },
+  { 0.1, 0.1, 0.1, 0.1, 0.1, 0.3, 0.4, 0.5, 0.1, 0.6, 1.0, 1.0, 1.0, 0.6, 0.5, 0.7, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 0.7, 0.5, 0.3, 0.3, },
 };
 
-static float ringCorrectionFactor[NCCL_NUM_PROTOCOLS][25] = {
-  { 0.4, 0.6, 0.6, 0.3, 0.2, 0.2, 0.2, 0.2, 0.4, 0.6, 0.7, 0.9, 1.4, 1.5, 1.0, 0.8, 0.7, 0.8, 0.8, 0.9, 0.9, 0.9, 0.9, 0.9, 0.9, },
-  { 0.4, 0.6, 0.6, 0.3, 0.2, 0.2, 0.2, 0.2, 0.4, 0.6, 0.7, 0.9, 1.4, 1.5, 1.0, 0.8, 0.7, 0.8, 0.8, 0.9, 0.9, 0.9, 0.9, 0.9, 0.9, },
-  { 0.6, 0.4, 0.4, 0.4, 0.2, 0.3, 0.2, 0.2, 0.2, 0.2, 0.2, 0.2, 0.2, 0.2, 0.2, 0.2, 0.2, 0.3, 0.4, 0.6, 0.8, 0.9, 1.1, 2.0, 2.9, },
+static float ringCorrectionFactor[NCCL_NUM_PROTOCOLS][27] = {
+  { 1.0, 0.5, 1.0, 1.0, 0.6, 0.7, 1.0, 1.0, 0.2, 1.0, 0.9, 0.7, 1.0, 1.0, 1.0, 0.9, 0.9, 0.8, 0.8, 0.7, 0.6, 0.5, 0.5, 0.3, 0.2, 0.1, 0.1, },
+  { 1.0, 0.5, 1.0, 1.0, 0.6, 0.7, 1.0, 1.0, 0.2, 1.0, 0.9, 0.7, 1.0, 1.0, 1.0, 0.9, 0.9, 0.8, 0.8, 0.7, 0.6, 0.5, 0.5, 0.3, 0.2, 0.1, 0.1, },
+  { 0.3, 1.0, 0.3, 0.1, 0.1, 0.1, 0.3, 0.7, 1.0, 0.2, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.2, 0.3, 0.5, 0.9, 1.0, 1.0, 1.0, 1.0, },
 };
 
+
 ncclResult_t ncclTopoGetAlgoTime(struct ncclInfo* info, int algorithm, int protocol, int numPipeOps, float* time) {
   float bw = info->comm->bandwidths[info->coll][algorithm][protocol];
   float lat = info->comm->latencies[info->coll][algorithm][protocol];
@@ -304,12 +304,12 @@ ncclResult_t ncclTopoGetAlgoTime(struct ncclInfo* info, int algorithm, int proto
 
 #if defined(__HIP_PLATFORM_HCC__) || defined(__HCC__) || defined(__HIPCC__)
   if (algorithm == NCCL_ALGO_TREE) {
-    if (logSize < 25) bw *= treeCorrectionFactor[protocol][logSize];
-    else bw *= treeCorrectionFactor[protocol][24];
+    if (logSize < 27) bw *= treeCorrectionFactor[protocol][logSize];
+    else bw *= treeCorrectionFactor[protocol][26];
   }
   else if (algorithm == NCCL_ALGO_RING) {
-    if(logSize < 25) bw *= ringCorrectionFactor[protocol][logSize];
-    else bw *= ringCorrectionFactor[protocol][24];
+    if(logSize < 27) bw *= ringCorrectionFactor[protocol][logSize];
+    else bw *= ringCorrectionFactor[protocol][26];
   }
 #else
   if (algorithm == NCCL_ALGO_TREE && logSize < 23) bw *= treeCorrectionFactor[protocol][logSize];