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What I was referring to was the way the leasing companies did business. IBM charged rental fees based on the machine purchase price spread over 5 years. IBM didn't want to sell their mainframes at all, they only did so because of the 1956 consent decree. The leasing companies bought 360s and leased them to customers for the purchase price spread over 7 years, thus beating IBM's rental for the same equipment. If the customer returned the machine before that time, the leasing company lost money. That's why they (the leasing companies) were desperate to keep their 360s viable. IBM hoped the 370s would kill them off, both the 360s and the leasing companies.
IBM's plans were revealed in memos during the anbreastrust trial. Ever wonder why IBM introduced the 3330 drives only for the 370s and not the 360s? Why no 370-compatible DAT box was offered for any 360? These weren't technical issues, they were decisions driven by business and financial concerns.
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there was a 360 DAT box available on the 360-65 ... it was called the 360-67. DAT-virtual memory was...
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one of the issues of applying scarce resources to bldg new stuff or niche markets...
Of course, what IBM didn't do, the leasing companies and clone makers did. In the source code for version 21.8F of OS-360 available with the Hercules emulator there are two versions of IPLNIP: the standard IBM one, and one modified by Itel (a major leasing company) to include not only support for 3330 drives, but a "370 instruction simulator" so 360s could execute (however slowly) 370 code. Reminders of the desperate technical efforts to keep the 360s alive when IBM was doing everything it could to force-march everyone to the 370.