[OpenBIOS] OpenBIOS POST, flash, and IO card site.

Chris Davis cjdavis at t-systems.com
Tue Jul 6 13:44:41 CEST 1999


For a number of reasons, this circuit is not going to work. Among

1. You've hooked up IO Read and IO Write - this puts the Flash in the
IO space, not the memory space. You need MEMRead and MEMWrite

2. On the actual hardware that I have seen out there, segment F000h is
not sent to the ISA bus at all. In fact, most modern chipsets have a
totally separate data bus for the flash and other peripherals - so you
will never see any access to your boot board. We have used both
techniques on boards that we have designed in the past.

3. Even if you find a board that decodes F000 to the ISA bus, you will
now have bus contention between your board and the old standard flash
on the motherboard. Not a problem if the flash is socketed, but many
boards (some of ours, for example) have soldered flash, making this
non-trivial as well.

Given these major issues, here are a couple of alternatives:

- You could build a small carrier board to plug into the flash socket
on your motherboard which would hold 2 flash chips and some sort of
decoder that will switch between them under software control.

- build support for boot-block flash into OpenBIOS.

Sorry for the bad news, but there are still options for some little
hardware-hacking projects..


-----Original Message-----
From: owner-openbios at elvis.informatik.uni-freiburg.de
[mailto:owner-openbios at elvis.informatik.uni-freiburg.de]On Behalf Of
James Oakley
Sent: Monday, July 05, 1999 7:25 PM
To: openbios at elvis.informatik.uni-freiburg.de
Subject: [OpenBIOS] OpenBIOS POST, flash, and IO card site.

I've placed the schematics on my website at
http://wiley246h122.roadrunner.nf.net:2080/openbios/ (yes, it's a
address) for the OpenBIOS development hardware. There is currently no
documentation, but the circuit is, in a way, straightforward.

If anybody can check it over and verify if it's correct I will be
forever in your debt.

For those who don't know, this is a single ISA card that allows
dual-flash functionality, standard port 0x80 POST, enhanced OpenBIOS
POST (to character LCD, actually human-readable!), and 5
8bit IO ports (for experimentation, education, and embedded designs).

Feel free to contact me on any issues here.

James Oakley
jfunk at roadrunner.nf.net
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