CompuServe Messages

DC >>Do you know anything about how the MASK works?<< I believe it deals with "where" within the Amiga's memory, the data can be DMA'd. And whether the transfers are 32-bit, 16-bit, or 8-bit in alignment. — The MASK is the highest area of memory (in BITS) that is accepted as a viable DMA area. The last digit of the MASK (c, e, or f) marks the alignment as 32, 16, or 8 bit. (If I got my math & facts right…) A mask of 0xfffffe = 16,777,215 bits (2-megs). This allows DMA transfers to the first 2-megs of address space, but doesn't allow for DMA transfers to other memory areas.. This would be the CHIP memory area. A mask of 0x7fffffe = 134,217,726 bits (16-megs). This labels the first 16-megs of address space as an approved DMA area. This would allow DMA transfers from HD to CHIP RAM, FAST RAM (Zorro-II), and Slow-Fast (if it is DMA'able). A mask of 0x7ffffffe = 2,147,483,647 bits (256-megs). This is first 256-megs of address space, which would include CHIP, FAST (Zorro-II), Slow-Fast, and the A3000/4000 motherboard memory, & A3000/4000 co-processor slot RAM. — The last digit of the mask affects whether the transfer is to be an 8-bit, 16-bit, or 32-bit transfer. 0x7fffffff = 8 bit alignment 0x7ffffffe = 16 bit alignment 0x7ffffffc = 32 bit alignment Since my A1200 has 32-bit memory, I use "0x7ffffffc" for EACH partition. This should allow me to have HD transfers aligned with my 32-bit FAST RAM. Also, the MAXTRANSFER rate should be '0x1fe00' for EACH partition of an IDE hard drive. Ron. – ("I'm not stupid, I'm not expendable, and I'm not going!" – quote made by any low level RPG player.)