diff --git a/projects/rccl/src/graph/paths.cc b/projects/rccl/src/graph/paths.cc
index c53f15766d..61055eeb38 100644
--- a/projects/rccl/src/graph/paths.cc
+++ b/projects/rccl/src/graph/paths.cc
@@ -591,7 +591,7 @@ ncclResult_t ncclTopoGetIntermediateRank(struct ncclTopoSystem* system, int rank
   }
   return ncclSuccess;
 }
-
+// Default value of PXN_DISABLE may be overwritten by changes in src/rccl_wrap.cc
 NCCL_PARAM(PxnDisable, "PXN_DISABLE", 1);
 
 // Net v4 plugins don't have non-blocking connect/accept. We can't therefore use
@@ -603,7 +603,8 @@ int ncclPxnDisable(struct ncclComm* comm) {
       INFO(NCCL_INIT, "PXN Disabled as plugin is v4");
       pxnDisable = 1;
     } else {
-      pxnDisable = ncclParamPxnDisable();
+      rcclSetPxn(comm, pxnDisable);
+      pxnDisable = (pxnDisable > RCCL_VALUE_INVALID)? pxnDisable : ncclParamPxnDisable();
     }
   }
   return pxnDisable;
diff --git a/projects/rccl/src/include/rccl_common.h b/projects/rccl/src/include/rccl_common.h
index f29096a618..914dc2c9ed 100644
--- a/projects/rccl/src/include/rccl_common.h
+++ b/projects/rccl/src/include/rccl_common.h
@@ -41,6 +41,11 @@ typedef enum RcclTunableColls {
 #define RCCL_PROTOCOL_FACTOR_IDX 2
 #define RCCL_PROTOCOL_THREAD_THRESHOLD_IDX 3
 
+typedef enum {
+  RCCL_VALUE_UNSET = -2,
+  RCCL_VALUE_INVALID = -1
+} rcclValueState_t;
+
 #ifdef RCCL_EXPOSE_STATIC
 #define RCCL_STATIC_EXPOSE_CHECK()
 #else
@@ -78,7 +83,8 @@ void rcclUpdateThreadThreshold(struct ncclComm* comm, size_t const& nBytes, stru
 ncclResult_t rcclGetAlgoInfo(struct ncclComm* comm, ncclFunc_t coll, uint64_t count, ncclDataType_t dataType,
                              int collNetSupport, int nvlsSupport, int numPipeOps,
                              int* algo, int* protocol, int* maxChannels);
-
+void rcclSetPxn(struct ncclComm* comm,  int& rcclPxnDisable);
+void rcclSetP2pNetChunkSize(struct ncclComm* comm,  int& rcclP2pNetChunkSize);
 ncclResult_t rcclFuncMaxSendRecvCount(ncclFunc_t func, int nRanks, size_t count, size_t& maxCount);
 ncclResult_t commSetUnrollFactor(struct ncclComm* comm);
 #endif
diff --git a/projects/rccl/src/init.cc b/projects/rccl/src/init.cc
index 16a8a6179a..e8a8ca79e8 100644
--- a/projects/rccl/src/init.cc
+++ b/projects/rccl/src/init.cc
@@ -396,7 +396,7 @@ static ncclResult_t commFree(ncclComm_t comm) {
       WARN("%s", comm->proxyState->proxyTrace->dump().c_str());
     }
   }
-  
+
 
 #ifdef ENABLE_PROFILING
   struct ncclProf *prof, *prof_seq;
@@ -981,7 +981,7 @@ static ncclResult_t setupChannel(struct ncclComm* comm, int channelId, int rank,
 NCCL_PARAM(BuffSize, "BUFFSIZE", -2);
 NCCL_PARAM(LlBuffSize, "LL_BUFFSIZE", -2);
 NCCL_PARAM(Ll128BuffSize, "LL128_BUFFSIZE", -2);
-
+// Default value of P2P_NET_CHUNKSIZE may be overwritten by changes in src/rccl_wrap.cc
 NCCL_PARAM(P2pNetChunkSize, "P2P_NET_CHUNKSIZE", (1 << 17)); /* 128 kB */
 NCCL_PARAM(P2pPciChunkSize, "P2P_PCI_CHUNKSIZE", (1 << 17)); /* 128 kB */
 NCCL_PARAM(P2pNvlChunkSize, "P2P_NVL_CHUNKSIZE", (1 << 19)); /* 512 kB */
@@ -994,7 +994,10 @@ static ncclResult_t computeBuffSizes(struct ncclComm* comm) {
     comm->buffSizes[p] = envs[p] != -2 ? envs[p] : defaults[p];
   }
 
-  if (comm->nNodes > 1) comm->p2pChunkSize = ncclParamP2pNetChunkSize();
+  if (comm->nNodes > 1) {
+    rcclSetP2pNetChunkSize(comm, comm->p2pChunkSize);
+    comm->p2pChunkSize = (comm->p2pChunkSize > RCCL_VALUE_INVALID)? comm->p2pChunkSize :  ncclParamP2pNetChunkSize();
+  }
   else if (comm->isAllNvlink) comm->p2pChunkSize = ncclParamP2pNvlChunkSize();
   else comm->p2pChunkSize = ncclParamP2pPciChunkSize();
 
diff --git a/projects/rccl/src/rccl_wrap.cc b/projects/rccl/src/rccl_wrap.cc
index 0ef494961a..162df74862 100644
--- a/projects/rccl/src/rccl_wrap.cc
+++ b/projects/rccl/src/rccl_wrap.cc
@@ -120,6 +120,33 @@ ncclResult_t rcclGetAlgoInfo(struct ncclComm* comm, ncclFunc_t coll, uint64_t co
   return ncclSuccess;
 }
 
+void rcclSetPxn(struct ncclComm* comm,  int& rcclPxnDisable) {
+  static int pxnDisable = RCCL_VALUE_UNSET;
+  if(pxnDisable == RCCL_VALUE_UNSET) {
+    const char *inputStr = getenv("NCCL_PXN_DISABLE");
+    if(!IsArchMatch(comm->topo->nodes[GPU].nodes[0].gpu.gcn, "gfx942") || inputStr) {
+      rcclPxnDisable = pxnDisable = RCCL_VALUE_INVALID;
+      return;
+    }
+    pxnDisable = (comm->nRanks >= 64)? 0 : 1;
+    INFO(NCCL_INIT, "RCCL PXN set as %s", !pxnDisable? "enabled" : "disabled");
+  }
+  rcclPxnDisable = pxnDisable;
+}
+
+void rcclSetP2pNetChunkSize(struct ncclComm* comm,  int& rcclP2pNetChunkSize) {
+  static int p2pNetChunkSize = RCCL_VALUE_UNSET;
+  if(p2pNetChunkSize == RCCL_VALUE_UNSET) {
+    const char *inputStr = getenv("NCCL_P2P_NET_CHUNKSIZE");
+    if(!IsArchMatch(comm->topo->nodes[GPU].nodes[0].gpu.gcn, "gfx942") || inputStr) {
+      rcclP2pNetChunkSize = p2pNetChunkSize = RCCL_VALUE_INVALID;
+      return;
+    }
+    p2pNetChunkSize = (comm->nRanks >= 64)? (1 << 19) : (1 << 17);
+    INFO(NCCL_INIT, "RCCL P2P net chunk size default set to: %d", p2pNetChunkSize);
+  }
+  rcclP2pNetChunkSize = p2pNetChunkSize;
+}
 
 ncclResult_t rcclFuncMaxSendRecvCount(ncclFunc_t func, int nRanks, size_t count, size_t& maxCount) {
   RCCL_STATIC_EXPOSE_CHECK();