[...]
static int hddcachereadsectors = 0;
[...]
int fat_read( struct fat_file *file, int sectorcount, void* buf )
{
    int cluster = file->nextcluster;
    int sector = file->nextsector;
    int numsec = file->sectornum;
    int err, i;

    if ( sector == -1 )
        return 0;

    for ( i=0; i<sectorcount; i++ ) {
        err = ata_read_sectors(sector + fat_bpb.startsector, 1,
                               (char*)buf+(i*SECTOR_SIZE));
        if(err) {
            DEBUGF( "fat_read() - Couldn't read sector %d"
                    " (error code %d)\n", sector,err);
            return -1;
        }

        numsec++;
        if ( numsec >= fat_bpb.bpb_secperclus ) {
            cluster = get_next_cluster(cluster);
            if (!cluster) {
                /* end of file */
                sector = -1;
                break;
            }
            
            sector = cluster2sec(cluster);
            if (sector<0)
                return -1;
            numsec=0;
        }
        else
            sector++;
    }
    file->nextcluster = cluster;
    file->nextsector = sector;
    file->sectornum = numsec;

    // read more sectors to fill hdd cache (every 2nd read)
    
    hddcachereadsectors = !hddcachereadsectors;
    
    if (hddcachereadsectors) {
    
    for ( i=0; i<sectorcount; i++ ) {
        err = ata_read_sectors(sector + fat_bpb.startsector, 1,
                               (char*)buf+((sectorcount-1)*SECTOR_SIZE)); 
                               // overwrite a part of the buffer
                               // doesn't matter, I only want to test the
                               // time between spinups..
        if(err) {
            DEBUGF( "fat_read() - Couldn't read sector %d"
                    " (error code %d)\n", sector,err);
            return -1;
        }

        numsec++;
        if ( numsec >= fat_bpb.bpb_secperclus ) {
            cluster = get_next_cluster(cluster);
            if (!cluster) {
                /* end of file */
                sector = -1;
                break;
            }
            
            sector = cluster2sec(cluster);
            if (sector<0)
                return -1;
            numsec=0;
        }
        else
            sector++;
            
    }
}    
    return sectorcount;
}