Diskless Linux, boot from flash

[yawn@emacinc.com]

	OK, from the truly sick and twisted department...

M-Systems makes a flash device called a DiskOnChip.  At boot time, the DoC will hook
the BIOS and install its own drivers (DOS-only) and look just like a real disk
drive.  The BIOS can then load and boot an operating system from the device (load a
Linux system into ramdisk, for example).  As a bonus, two different Linux drivers
exist for the thing, one Free (kinda shaky) and one not Free (rock solid).  Thus,
you could actually use the thing as a root filesystem.  An 8MB DoC costs about $50.

The DoC has the same pinout as a 32-pin EPROM, and its plugs pretty much straight
into the ISA bus.  If you're so-minded, you can wire-wrap an ISA card for the
thing.  If you're in a hurry, you can buy a $40 card just to plug the thing in.

Now for the really twisted part:  The DoC pinout is the same as you might find on a
NIC's boot ROM socket.  It's also the kind you'd see in a BIOS extension card (like
one of the Y2K upgrade cards, or a BIOS upgrade to fix the large IDE drive problem
my old 486 had).  Many NICs have 28-pin sockets (which are compatible with some
work), but at least 1 3com card I've seen ha a 32-pin socket.  Now, IN THEORY, a
DiskOnChip should work when plugged into one of these boot ROM sockets, with one
caveat:  a boot ROM is a read-only device, and therefore a boot ROM socket might not
have the write strobe wired up.  a DoC is a read/write device, and so needs the
write line (even if you're using the DoC as a read-only boot device, it' still
paged).  Now I've never done this myself, but it MIGHT work.  And I'm really curious
to see if it does.  Let me know if you try it, OK?  And let me know if you have any
questions about it too...


Nathan Yawn


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