::SHE+ILA:: Goes Far, and LBA formats change [14]

More about ::SHE+ILA:: Goes Far, and LBA formats change [14]

As discussed in picture [13], maintaining both Near (16bit) and Far (32bit) addresses was too unweildy, so we have now got rid of 16bit addresses. References within the same page will now be 32bit with the high-order 16bits zeroised.Thus Buf headers and Dope Vectors all have 4byte addresses and lengths. The source code (#asm) will be updated soon.
The LBA fields in the GHOST and the first page of a multipage segment now has 3byte page numbers, allowing 2^24 = 4 megapages. The system page size is now 64K (was 32K) as it makes better use of the 16bit offset within a page, thus the LBA as sent to the disk device driver has 5 bytes, giving a maximum partition size of 2^40 = 1 Terabyte. It could someday be increased to 6 byte (48bit) LBA's, allowing 2^48 (=256 Terabyte) drives, but that's plenty for now :) The "directory" page of a multipage segment will hold 64K / 3 LBA entries (each aligned to a 64K disk page boundary, the rightmost 8 bits being implied zeroes), allowing just over 20,000 pages per segment. Subsequent "directory" pages could increase this to, say, 64K pages per segment (though ::SHE+ILA:: was not designed to have a datastore that large) if we have three "directory" pages at the beginning of a segment.
LBA entries within the page table will also now be 3 bytes each, again with two implied rightmost zero bytes. The size of the page table will grow slightly due to the LBA field growing; the number of page table entries still depending on the amount of RAM used for the page frames (default = 1GB, which holds 2^(30-16) = 16,000 page frames (each of 64K bytes).