The midseventies SHARE survey 70

there was a 360 DAT box available on the 360-65 ... it was called the 360-67.

DAT-virtual memory was really expensive in 360 technology and tended to consume larger amounts of real memory .... but could more efficiently manage large amounts of real memory (in general the virtual memory versions of the kernels had larger fixed memory sizes and tended to have larger application space requirements for the minimum configuration). The 360-generation disk drives had much lower transfer speeds than the 3330, making 3330 really only practical on the higher-end 370s). There was also a recognized heavy channel busy burden doing 360 CKD seek-search-IO operations and as a result, 3330 also introduced new technology allowing channel disconnect during disk rotation operation ... which in turn required new kind of block multiplexor channel technology.

even retrofitting DAT hardware to 370-155 and 370-165 was a difficult and expensive process. The full 370 architecture called for some amount more stuff than was eventually made available to customers. There were some combined engineering, architecture and software meetings in POK where the 370-165 engineers said that it would delay announce and delivery by an additional six months if they had to engineer the full 370 virtual memory architecture specification. So as a result ... only a subset of the 370 virtual memory architecture was announced and shipped (based on what the 370-165 engineering schedule could actually handle).

some of these arguments could probably also be made about car manufactors ... why don't you see more car manufactors retrofitting 3-4 year old models with 2005 bodies and interiors.

If you are talking about field upgrade of existing 360s to accomodate all the various bits & pieces of technology introduced in 370 ... you could be talking about nearly a complete swap (except for possibly the covers).

most of the attention and effort was going to future system stuff (with 370 activity actually only by a somewhat minor side issue)

problem was that future system failed and was eventually cancelled w-o ever being announced (and then there was enormous effort to play technology catchup with 370 because of all the lost years spent on fs):

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