Hi!
16-Фев-2004 17:49 [EMAIL PROTECTED] (tom ehlert) wrote to "Arkady V.Belousov"
<[EMAIL PROTECTED]>:
AVB>> Current boot.asm (fat12/fat16) reads complete FAT into memory (for
AVB>> FAT16 it may be up to 128k), then converts FAT chain to array of file
AVB>> clusters. On the other side, boot32* (for each next cluster) reads only
AVB>> required FAT sector (but not reread already readed sector). In ideal, when
AVB>> all clusters in chain fir into one sector, this reduces reads by one sector.
AVB>> I think, this will be useful, especially for floppies. Any objections?
te> objection:
te> 32 bit sectors for fat12/fat16 are useless,
? Sectors in all boot code (boot.asm, boot32.asm, boot32lb.asm) are
32-bit values.
te> as they unnecessarily increase number of different bootsectors.
I not say about "different bootsectors", I only say, that I suggest,
that making FAT reading more lazy (reading only necessary FAT sectors,
one at a time) should make booting faster.
te> I personally don't mind a single fat32 for >= 386; FAT32 for 80186 is
te> plain ridiculous.
This is another question. There are three options: target CPU (8086 or
386+; 8086 also works on 386+), acces method (LBA or CHS) and file system
(FAT1x and FAT32). To join FAT1x and FAT32 in one 512-bytes sector there are
no chances, so should be (at least) two boot sectors: FAT1x and FAT32.
Fortunately, in FAT1x boot sector for 8086 is enough space for both LBA
and CHS. But FAT32 currently splitted by two boot sectors - FAT32+8086+CHS
and FAT32+386+LBA. After optimizations I may join CHS and LBA in FAT32, but
with 8086 target there are (yet) no space for any other change (for example,
make nicer messages).
But again: quoted above sentences relate only to _functional
optimization_ (speeduping loadinf) for FAT1x boot sector. FAT32 there I
mention only as example.
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