Date: Wed, 3 Jan 1996 17:52:31 +0100 (MET) From: J Wunsch <j@uriah.heep.sax.de> To: freebsd-hackers@freebsd.org (FreeBSD hackers) Subject: Re: POST checksum hacking Message-ID: <199601031652.RAA20736@uriah.heep.sax.de> In-Reply-To: <199601030920.CAA24493@seagull.rtd.com> from "Don Yuniskis" at Jan 3, 96 02:20:33 am
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As Don Yuniskis wrote: > > I'd like to cut a new set of EPROMs with an altered disk table > but the POST screams about bad checksums. Anyone have a clue as > to the algorithm employed and the location of the checksum image > (before I start disassembling code)? A ROM image consists of 0x55 0xaa - signature <len> - number of 512-byte ``increments'' this ROM consists of <len>*512-3 bytes ROM image The entire ROM image must byte-checksum to 0. This is usually done by placing a jump next after the <len> byte, and reserving the byte after the jump instruction for checksumming. (I haven't verified this information.) -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)
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