Thanks for your answer. I was aware about the fact that most biosses use a mix of different banks. According to the leaked MCPX code, the xcodes are fetched from bank 0. The original Cromwell and gentoox bios (256MB versions) used bank 3 to find their Kernel, and also had the bootrom ld file setup so that the 2bl was copied from bank 3 to ram. I changed those settings so that both point to bank 0. Xblast_os already worked that way. The modified bios combined with some others in bank 1 2 and 3 work fine in xqemu. (Besides a problem with the controller emulation which is an xqemu issue and not a bios one.) When I tsop flash them on an xbox, they won't boot. I checked how xqemu loads it's bios files, and it is loading the whole 1MB, so it's not like it's only using 256MB and replicating that area. So basically, there is something on the real xbox that needs another bank . I had noticed that xblast_os starts it's 2bl at another address, but it's only the 2 last instructions of the xcode that need to be checked for that. Since it run's on a modchip and on xqemu, I assume there is no problem there. Do you still have some modchips for sale, or do you intend to produce another batch? Is it possible to alter the LPC bus behavour on it? I am trying to modify a chihiro bios so that it run's on a retail mobo with 128MB ram. Without the other 2 chihiro boards connected, it simply isn't showing any video. I remember reading somewhere that your modchip was responding to the commands queuering for the other board id's. It could be usefull for testing the new bios without the other 2 boards.
I remember doing this now(I,ve done so much stuff it hard to recollect what was modified). I did it when I moved the 2bl starting offset in the image. I never understood why other BIOSes do it differently. It just make so much more sense to load everything from the same bank image... That's weird but I think there few MCPX IC revisions in early Xbox consoles. Maybe the supported dumped image in XQEMU isn't the same revision as the one in your physical Xbox console? No problem there, all other BIOSes use 0x1000 as 2bl starting offset just because MS stock BIOS used that. Since BIOS development, specifically regarding Xcodes, basic init and 2bl unpack is basically dead, I figured I could get back a few bytes of rom space by moving the 2bl right next to the Xcodes (instead of having a gap of nothing between them!). Frankly I don't know right now... The batch of "Pre-Edition" I have isn't sold out yet and I figured if these don't sell well, I don't think it would be justified for me to drop $3000USD for a batch if I'm left with most of them unsold... What do you mean by that? XBlast Lite's HDL code respond to a couple of offsets in memory because they need to be addressed at any time while the console is active. However, due to space contraint in the CPLD, there is no user configurable register space... If I recall well, the XBlast Lite will report 2 things that are Chihiro related. MediaBoard revision and DIMM size. MediaBoard revision is set to "FPGA" (other valid choice is ASIC) and DIMM size to 1024MB. I have absolutely no idea if it's going to be of any benefit to your goal. In fact, it could make things worst as the console is reporting a MediaBoard with 1024MB DIMM when there is none in reality. I just implemented this feature because there was almost no cost in terms of ressource to add it and didn't cause any trouble with normal Xbox operations.