This may be a bit off topic, I'm not sure. But I'm curious about the design decision on some of the instructions. Basically, the ones like MVCLE which can complete with a CC=3 to indicate that they didn't process all the data. This versus "Interruptable Instructions" such as MVCL, which can also be stopped before processing all the data. In the first case, you can simply JO back to the instruction to continue. In the second, things such as the registers are set up properly and the PSW is not updated so that when the system redispatches the work, the instruction PSW points to the interrupted instruction and no branching in the user code is required. I hope I'm making sense.
My curiosity is why MVCLE sets the CC, thus forcing user code to branch back. Why not just not update the PSW instruction address until all the data is processed? Still allow the interrupt like MVCL does, of course. I understand why the interrupt is necessary, especially in a single CP environment. Does anybody know? Is it a "millicode" thing? John McKown Systems Engineer IV IT Administrative Services Group HealthMarkets(r) 9151 Boulevard 26 * N. Richland Hills * TX 76010 (817) 255-3225 phone * [email protected] * www.HealthMarkets.com Confidentiality Notice: This e-mail message may contain confidential or proprietary information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message. HealthMarkets(r) is the brand name for products underwritten and issued by the insurance subsidiaries of HealthMarkets, Inc. -The Chesapeake Life Insurance Company(r), Mid-West National Life Insurance Company of TennesseeSM and The MEGA Life and Health Insurance Company.SM
