Timeline for What limited the use of the 6809 CPU in personal computers?
Current License: CC BY-SA 4.0
8 events
| when toggle format | what | by | license | comment | |
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| Mar 5, 2023 at 18:02 | comment | added | user693336 | The 6809 was a great CPU at the time. However, it was a little late to the party, was too costly when released, and when the price did come down it was shown-up by the new 16 and 32-bit CPUs like the 68008 and 68000. Motorola could have made a killing if they had reduced the price to compete with the Z80 and 6502. It was used in many not so popular (in the US anyway) home computers. I was told by a retired NASA EE it was used as a cargo door controller on the SST-1 (Columbia Space Shuttle). I still have a soft spot for the 6809. Not sure if anyone still manufactures it. They are open cores. | |
| Jul 27, 2021 at 17:17 | comment | added | supercat | ...the desired constant value somewhere in code, and putting its address in the instruction). If one tries to write code in the style of the "huge" memory model, the 8086 instruction set will be horrible to work with, but if one designs code to work with the design of 8086 segments it's really quite nice. Too bad the designers of the 80286 and 80386 failed to understand what was good about 8086 segments, since otherwise the principles could be extremely useful in frameworks like .NET and Java. | |
| Jul 27, 2021 at 17:15 | comment | added | supercat | @PatrickSchlüter: IMHO, the 8086 segment design is vastly under-appreciated. I think there should have been a processor status bit to control whether the default segment is DS or SS, along with a DS prefix for use in the latter scenario, so that applications where stack and global data total 64K or less could have two "free" segment registers rather than one, and dev tools had some unfortunate limitations (e.g. assemblers could have allowed a programmer to request that a segment register be loaded with a constant, and handled that by generating cs:mov ds,[someAddr] putting... | |
| Jul 26, 2021 at 7:32 | comment | added | Patrick Schlüter | I suppose he meant the inbuilt access to 1 MiB via segments which 6809 would need some external, non standard, circuit to implement anything to overcome the 64 KiB address limit. While x86 segments were annoying when the 1 MiB limit was reached, it was quite usefull and simple to overcome the 64K limit. | |
| Jul 25, 2021 at 16:34 | review | Late answers | |||
| Jul 25, 2021 at 17:31 | |||||
| Jul 25, 2021 at 16:20 | comment | added | user3840170 | The x86 line had no form of MMU until the 80286. What are you referring to? | |
| Jul 25, 2021 at 16:15 | review | First posts | |||
| Jul 25, 2021 at 16:20 | |||||
| Jul 25, 2021 at 16:13 | history | answered | Ken F Lantz | CC BY-SA 4.0 |