Why is my 2015 Late model wirh one Terabyte (one Drive) iMac as slow as old eMacs nearly- 50 to access memory it has DRAM but thought it was only for olderlow access not all-its all-its too slow to me doing an IMAC work needed one with flash I fear

You have a late 2015? If this is your model:

https://everymac.com/systems/apple/imac/specs/imac-core-i5-2.8-21-inch-aluminum-late-2015-specs.html

then you have the entry level iMac with a snail like super slow 5400 rpm hard drive. It does everything super slow. And, if you have the minimum 8 GB RAM, it makes it worse.

You can download, run, and post the results of a free diagnostic tool app using the third little icon from the right in the tool bar of the reply window - it is available at the developer' s site or the app store:

www.etrecheck.com

I think we have a bit of a misunderstanding here: there is RAM modules which is the memory. 8 GB is now considered the minimum; 16 much better and if you're into videos/movie rendering/etc, 32 is better. Then there is the hard drive - nothing at all to do with memory - it is the space where all of your files, etc. including the OS and system files are "parked". It is also the place where anything you do takes place. The old spinning drives were just that: much like a DVD or record player, it would spin and data would be written to it. If it was the slow one, it would spin and read/write slowly; nowadays, there are SSDs which are much much faster but the basic concept of storage is still the same.

You just need to dig for the tech specs of the machines. iMacs are great - I got a refurb 21.5" iMac from Apple with a 512 GB SSD as a hard drive (the default for those 21.5" was also a slow 5400 rpm spinning drive, but this one was custom configured with an SSD and 16 GB of RAM). Works like a charm.