On 12/13/2017 03:37 PM, Dave Howorth wrote:
On Wed, 13 Dec 2017 09:48:50 -0500 James Knott <james.knott@rogers.com> wrote:
On 12/13/2017 09:27 AM, Carlos E. R. wrote:
Program counter, stack counter, flags... All "CPU" registers. Stack pointer, not counter. It pointed to the location where the registers were saved/read. Most machines with core memory didn't have stack pointers. Hardware support for stacks was rather late.
They didn't have CPUs either. Processing would be split between the arithmetic unit, or mill, the registers and the control unit.
You're talking to someone with a lot of experience with older gear. I spent years maintaining systems built with Data General Nova & Eclipse computers, along with DEC PDP-8 & PDP-11s. (I also worked on DEC VAX 11/780 and a couple of Pr1me computers.) In those systems, while there were not chips called "CPU", there were circuit boards. For example, the Data General computers had a 2 - 15" square board CPU. The Nova line used discrete logic, but the Eclipse used bit slice processors, AMD 2902 IIRC. It also had ROM with the microcode that programmed the instruction set. Back in those days, I worked right to the microcode level. The Nova had 4 registers, in addition to the program counter, and by using indirect addressing, a memory location could be used as a stack pointer. Compared to the Nova, the Intel 8080 CPU was, in some ways, advanced in comparison. My IMSAI 8080 had one of those. I believe the Eclipse may have had a stack pointer. It's been 28 years since I last worked with those DG & DEC computers. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org