New answers tagged microprocessor
1
There's also the TI-99/4A way of accessing more ROM and RAM than there is address space. The TMS-9900 has a 15 bit address bus and could therefore only address 32768 16 bit words. When one looks at the memory map of the TI-99/4A one can see that the console can address (theoretically) up to 32KiB+256 RAM, 16KiB VRAM, 8KiB + 2x8KiB ROM, 24KiB + 16x40KiB GROM ...
0
I wrote a rather large program for a DEC PDP 11-70 at the end of the 1970s, and once it broke through the 64k barrier, I had to go to Overlays. This meant manually partitioning the program into pages, so that any one page was self consistent. Very tedious and error-prone. I don't recall if the entire 64k had to be swapped for a different one each time, or ...
7
Another solution worth mentioning — although I doubt it was used by the systems you mention, and it merely allows addressing twice as much as 64K of memory — is "Split I&D", as rather famously used on later models of the PDP-11. A program could have 64K of memory for program text, and 64K of memory for data, for a total of 128K. The processor ...
15
There are a number of approaches that can allow a CPU with a 16-bit address bus to address more than 64kBytes of memory:
Bank Switching - explained in another answer,basicaly switching for example 8- or 16-kBytes blocks back and forth into the addressable range, so in effect exchanging the blocks with ones that are currently paged in. Some computers could ...
30
I don't know details of the Sharp PC-G830 specifically but the technique used to address more than 64K with a 16-bit address bus is called "bank switching".
This involves setting up some portions of memory to be switchable via an I/O port line and then the application program organizes things in memory such that different sections can be switched ...
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