Posted By
Litwr
on 2016-09-21
10:29:43
|  Re: What would I do differently in the Plus/4
I'd looked at 6509 data sheets. 6509 has only two instructions to work directly with 20 bit bus, LDA and STA. It was used with stylish CBM II. However 7501/8501 uses 7 lines for i/o...
JMP ($xFF) warp is documented at MOSTEC manual of 1976 so as warps of LDA $ff,X or LDA ($ff,X) for X > 0. I used it in the fast division routine. I had to add one byte for 65816 (SuperCPU) compatibility.
Yes, BCD is useful for scores. I'd used it with Xlife. However, BCD maybe evaded. BCD code makes addition/subtraction about 50% slower, and multiplication/division about 200% slower. It is only faster for the text input/output.
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