Hello devs, especially Jeremy, I reviewed your recent commit 1702 to build 2041 regarding sector sizes larger than 512. Here are my thoughts and suggestions.
- First, dsk.h defines the maximum sector size (MAX_SEC_SIZE) as 2048 (as the commit comment says) while the relevant LoL entry (maxsecsize) in kernel.asm is initialised to 4096. - Second, maxsecsize is erroneously used once in dsk.c while everything else uses the value from the dsk.h definition. - Third, if I'm not entirely mistaken, the patch makes all buffers grow to 2048 bytes, even in the absence of any block devices with large sectors. This will unnecessarily waste memory on most systems. MS-DOS initializes its 'maxsecsize' to 512 and will increase it (along with each buffer's size) during CONFIG processing whenever a block device with larger sectors is registered. (As far as I know/deduced, this works up to a sector size of 8192 bytes.) This way, if the need for large buffers wasn't apparent during CONFIG, they will stay smaller. This scheme could obviously be extended by additional tools/interfaces to increase the buffer size later on, and a CONFIG option to artificially increase it in anticipation of a post-CONFIG requirement. - Fourth, apart from the other points, I fail to see why you should not be able to simply increase MAX_SEC_SIZE to 8192. 4096 is definitely in need as evidenced by the list's requests for precisely that size. - Fifth, I think MS-DOS supports sector sizes below 512 too. If you were to look into that, I believe it wouldn't be too hard to implement. Due to the filesystem (size of directory entries), 32 bytes is the absolute minimum. I believe all sizes below 512 will require a slight change to the BPB loading (What to do about the sector end signature location?) while you might have to get creative for the very small sizes, because a full BPB would not fit. I'd suggest just expecting the BPB to stretch several sectors then; the filesystem already allows reserved sectors to be properly implemented using the BPB. Regards, C. Masloch ------------------------------------------------------------------------------ Try before you buy = See our experts in action! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-dev2 _______________________________________________ Freedos-kernel mailing list Freedos-kernel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-kernel
