Making a bootable CD howto

Hello,

I try this command in an Alphastation 250 running Openbsd 4.0 :
[root@alpha]# mkhybrid -r -b 4.0/alpha/floppy40.fs -c "boot.catalog" - 
o OpenBSD_alpha.iso OpenBSD

Size of boot image is 2880 sectors -> Emulating a 1.44 meg floppy
4.65% done, estimate finish Sat Sep 30 19:35:06 2006
...
97.63% done, estimate finish Sat Sep 30 19:35:14 2006
Total translation table size: 0
Total rockridge attributes bytes: 2693
Total directory bytes: 6144
Path table size(bytes): 36
Max brk space used 0
107555 extents written (210 Mb)

The folder content :

[root@alpha]#  ls -alR OpenBSD
total 16
drwxr-xr-x  3 root  wheel   512 Sep 30 19:00 .
drwxr-xr-x  3 root  wheel   512 Sep 30 16:52 ..
drwxr-xr-x  3 root  wheel   512 Sep 30 16:47 4.0
-rwxr--r--  1 root  wheel  2048 Sep 30 19:34 boot.catalog

OpenBSD/4.0:
total 12
drwxr-xr-x  3 root  wheel  512 Sep 30 16:47 .
drwxr-xr-x  3 root  wheel  512 Sep 30 19:00 ..
drwxr-xr-x  2 root  wheel  512 Sep 30 16:52 alpha

OpenBSD/4.0/alpha:
total 430908
drwxr-xr-x  2 root  wheel       512 Sep 30 16:52 .
drwxr-xr-x  3 root  wheel       512 Sep 30 16:47 ..
-rw-r--r--  1 root  wheel       417 Sep 30 16:47 CKSUM
-rw-r--r--  1 root  wheel     75108 Sep 30 16:47 INSTALL.alpha
-rw-r--r--  1 root  wheel       758 Sep 30 16:47 MD5
-rw-r--r--  1 root  wheel  49117491 Sep 30 16:48 base40.tgz
-rw-r--r--  1 root  wheel     40540 Sep 30 16:48 boot
-rw-r--r--  1 root  wheel      7680 Sep 30 16:48 bootxx
-rwxr-xr-x  1 root  wheel   7280742 Sep 30 16:48 bsd
-rwxr-xr-x  1 root  wheel   7280742 Sep 30 16:52 bsd.modified
-rw-r--r--  1 root  wheel   7280758 Sep 30 16:52 bsd.orig
-rw-r--r--  1 root  wheel   2292547 Sep 30 16:48 bsd.rd
-rw-r--r--  1 root  wheel   2402304 Sep 30 16:48 cd40.iso
-rw-r--r--  1 root  wheel  70114343 Sep 30 16:50 comp40.tgz
-rw-r--r--  1 root  wheel   1158926 Sep 30 16:50 etc40.tgz
-rw-r--r--  1 root  wheel   1474560 Sep 30 16:50 floppy40.fs
-rw-r--r--  1 root  wheel   1474560 Sep 30 16:50 floppyB40.fs
-rw-r--r--  1 root  wheel   2836904 Sep 30 16:50 game40.tgz
-rw-r--r--  1 root  wheel       213 Sep 30 16:50 index.txt
-rw-r--r--  1 root  wheel   7330840 Sep 30 16:50 man40.tgz
-rw-r--r--  1 root  wheel   2287053 Sep 30 16:50 misc40.tgz
-rw-r--r--  1 root  wheel     56556 Sep 30 16:50 netboot
-rw-r--r--  1 root  wheel  13344326 Sep 30 16:51 xbase40.tgz
-rw-r--r--  1 root  wheel     83304 Sep 30 16:51 xetc40.tgz
-rw-r--r--  1 root  wheel  33234892 Sep 30 16:52 xfont40.tgz
-rw-r--r--  1 root  wheel   8935658 Sep 30 16:52 xserv40.tgz
-rw-r--r--  1 root  wheel   2077127 Sep 30 16:52 xshare40.tgz


I burn this iso in a mac and when I try to boot, my Alphastation 250  
can not found the boot block.
It works with an "official" iso (cd40.iso burned in the same mac).

Thank's for your help

Emmanuel