STP Issue between DELL and CISCO

Hi Team,

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I came across to an issue that the STP increases the CPU on a cisco switch which is connected to a DELL EMC core switch. To give more details about the topology, I have to DELL EMC Core switches using VLT between them and and a stack of 2 cisco switches with port channels uplinks to to Cores. The cisco switches are running rpvst but the DELL switches are running pvst. Now my question now is if the cisco switches downgrade the verstion from rapid to normal pvstp in order to be compatible with the Dell ones and if so, could spanning tree could cause high CPU because it is being used between 2 different vendors?

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PS. Topology is 2 Dell Core switches with VLT between them and the cisco ones are the access layers switches pointing to Dell. Root bridges are the DELL

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Many thanks in advance