Does NT have a memory limitation

I am running NT4.0/spk6a on a Netfinity 7100 server with quad processors. I have 4 1gb memory modules, and 4 64mb memory modules. When booting up, the hardware counts all the memory, but once NT starts, it only sees the 4 gb of memory from the 4 1gb modules. Is there a patch or a registry edit that needs to be done in order to exceed this 4gb memory limitation that I’m running into?

Thanks….TJ