Microsoft Azure with AMD CPUs.
16 slots of DDR4-3200 RAM per socket. The largest capacity “cost effective” DIMMs today are 64 GB. Populated cost-efficiently, this server can hold of memory. Populated with specialized high-capacity DIMMs (which are generally slower than the smaller DIMMs), this server supports up to of memory total.
In AWS, one of the largest servers you can rent is the m6a.metal server. It offers 50 Gbps of network bandwidth, 192 vCPUs (96 physical cores), and 768 GB of memory, and costs $8.2944/hour in the US East region.
A similar server, with 128 physical cores and 512 GB of memory (as well as appropriate NICs, SSDs, and support contracts), can be purchased from the Dell website for about $40,000.