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| why did 70/80/90 only have 1 cpu if cpus where so slow? |
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| Brumby:
--- Quote from: abeyer on March 25, 2023, 10:11:42 pm ---... you can't just throw two cpus on the same memory bus and let them duke it out. --- End quote --- I didn't get past the title of this thread before this thought was screaming around my head. --- Quote --- They need to be designed to share a bus, or need to have separate memory spaces and some sort of communications channel. Either way adds hardware and software complexity and cost. --- End quote --- Indeed. Asking this question is, as others have stated, an indication that there is a distinct lack of understanding on how technology evolves. You could just as well ask why the Sopwith Camel didn't have a delta wing design. |
| Kleinstein:
Many of the early private computers in the 1970s/1980s were not really made to be fast. E.g. they still sold lots of 1 MHz 6502 systems when a 2 MHz version was available for not much more money. Adding a 2nd CPU add much most complications (e.g. SW compatibility) than just increasing the clock. So a faster clock was the more obvious way to more speed, not a 2nd parallel running CPU. Sharing a single task over 2 or more CPUs is by no means easy from the software side. Even now only some software can make real use of mulitple CPUs is the modern PCs. Without the SW support the second CPU is pretty useless and only adds costs and complications. The early mainframes with multiple CPUs often did separate tasks (e.g. different users) on the added CPUs, as this was the easier part and the coputers were anyway shared between users. To a certain degree I am wondering why the modern PCs do so many jobs with the main CPUs and not split of more tasks to dedicated parts. It would part with the old PC architecture, but it may be about time for that. |
| Siwastaja:
For the same reason multicore performance still sucks: it is very hard to write truly parallel (efficient at that) programs. People think in "do this, then do that" sequences, and reflect this thinking in programming languages. In order to get any advantage of multiple CPUs, you need to write programs like "do this, and simultaneously do that", and the problem then is getting everyone do useful work all the time and not just wait for others to finish their part of the result. It was way easier to just push performance up, to get job done earlier, so that next job can be started earlier; giving illusion of things being finished simultaneously. Only after physical limitations of how fast things can be done were hit, we had to start thinking how to do things simultaneously. |
| m k:
--- Quote from: aqarwaen on March 25, 2023, 09:47:35 pm ---if money was not issue,what would prevent 4 same cpus running in single system? --- End quote --- Check transputer. |
| tooki:
--- Quote from: aqarwaen on March 25, 2023, 09:47:35 pm ---so my question is why did 70/80/90 only have 1 cpu if cpus where so slow?if i understand most computer only had 1 single main cpu. for example why it was possible use for example multiple Intel 4004 instead single main cpu to make faster computers. if money was not issue,what would prevent 4 same cpus running in single system? --- End quote --- Gotta love questions that start with a premise that isn't even necessarily true, coming from the place of "I don't know anything about that topic, so I'll just make assumptions based on thin air". Note that the question just said "computer", not "personal computer", so this query technically includes minicomputers, servers, and mainframes, which commonly did have multiple processors. So there were multiprocessor systems back then, but they were expensive. Very expensive. Thus, "if money was not an issue" then very little prevented one from getting a multiprocessor system back then. |
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