For an analogy:
Imagine a city public transit system. It isn't a very large city, but it is a poor city. Nobody owns a car, so if it helps, imagine 3rd world setting. This one, lonesome bus is constantly transporting people around the city.
A memory heavy application is a bit like a family of 20 people, crammed into the bus station. It takes longer for them all to get on board, and get seated, and then when they arrive, it takes longer for them to collect their things and leave the bus.
This bus is the memory bus.
A multi-core machine has many bus stations, and only 1 bus. The problem with DF, is that it is a family of 50, and dividing that 50 person group up over 1 or even 50 bus stations still ends up completely filling the bus's seats, forcing other parties waiting at the station to wait even longer. By plugging up the whole bus, they bring the rest of the city's transport to a standstill.
Adding a GPU to the mix is like adding a fixed trolley line inside a gated community inside that city. To get to and from the gated community, you have to use the bus. To get around inside the gated community, you use the trolley. The trolley can have several different routes and cars running on the lines, depending on how it is laid out. By sending part of the family of 50 to the vgated community, and communicating by letters, you free up seats on the bus, and shorte the queue in the bus station. There are limits on how many people you can exchange between the bus ad the trolley line at any given time however; the more self-sufficient the gated community is, and the less it needs to exchange people with the city bus, the more efficiency is gained. The gated community has a shopping mall, and some some other useful/convenient features that let people do more with less travel, so they only use the city bus to get there and then go home.
NUMA is more like adding additional bus lines, where 1 bus travels only on the east side, 1 travels on the west side, one travels on the north side, and another on the south end.
These buses don't cross paths, but do have a central transit hub, which is also where the gated community's trolly line's station is.
To get from west side to north side, a rider rides the bus to the hub, disembarks, boards the north side bus, and then does their thing. This added step makes it inefficient for somebody in westside to go shopping in north side. As such, it makes much more sense to have local shops and businesses in west side for the west side resident to make use of, and only use the transit hub for special purchases. Even in this arrangement, the shops on the 4 'hoods are more open air, while the shops in the gated community are more mall/supermarket. There is still an advantage to send people with lots of luxury goods shopping needs to the gated community, because they can't be adequately serviced locally, and trying to get those goods from all over the city intails lots of waiting at bus stations.
Toady is basically saying "adding more bus stations won't improve the rate of transport, because there is only one bus, and it is a jesus-christ bus. It's not worth the expense. We need a bigger bus."
I am basically saying "that is currently true; however, the city is going to buy more busses, so planning your neighborhood to have more than one bus station hookup is prudent, even if it does nothing special right now. Doing it later after you have tent cities and shantytowns all over will make it much harder to put your bus stations in efficiently. You are going to have to rip some out and start over from scratch on civic planning if you wait."
To continue that analogy-- right now, the city is laid out with the premise that there is only 1 bus, and 1 bus station. All the shops and businesses in town are laid out by local resources and functions, such that all the city buildings are right next to each other, the fish restaraunt is next to the fishery, so the fish is very fresh, etc. If you want bread, you ride the bus to the baked goods street, which is nearby to the flour mills. All that sort of thing. The bus travels all over the city, and by minimizing the distances between related industries, you improve efficiency.
That does not work so well once you add seperate bus lines; now to get the breading for the fish at the fish restaurant, the cook has to board the bus, ride to the transit hub, wait around, ride the new bus to bakery street, get the breading, ride back to the transit hub, wait some more, ride the first bus again back to the restauraunt. By that time, the fish has been laying around too long and is not fit to cook.
The solution is to have fisheries, bakeries, and restauraunts in each quarter of the city, so that local transport is favored over external transport.
This means redesigning the city, and the way it is laid out.
Toady sayd "that's a lot of work! I prefer to add new shops in the different shopping districts, because that's more fun, and I don't see an advantage to adding more bus stations".
As stated above, I disagree with that view, because the longer he waits before modernizing the city, the harder it will be to modernize it later, when the new bus lines get mandated by the fed.