> Yes, this is in the definition of the standard. It must be, because on > power-up all registers (including &hA8) are zero. Therefore, the reset > routine (and thus the whole bios) must start at address 0, slot 0-0.
As far as I know, the standard doesn't say so. The problem is that there might be more than one MAIN ROM on MSXes which use for example a MSX -> MSX2 upgrade cartridge. The MSX1 rom in such a configuration will indeed be located in slot 0 or 0-0, but the MSX2 BIOS -which is the BIOS that should be used in such a configuration- will be located in another slot. The issue of accessing the right BIOS ROM is quite crucial. Consider for example direct VDP access. In an MSX1 with MSX2 upgrade cartridge, there will be two VDPs. The MSX1 VDP can be accessed through the usual in- and output ports, but the MSX2 VDP will use other ports, in case of the adapter I know of #88 and #89. The address of these ports can be only obtained by accessing #0006/#0007 in the MSX2 BIOS. The slot containing the BIOS which should be used on a MSX computer can be found at location #FCC1. MSX1 documentation claims that this address contains a byte indicating whether or not slot 0 is expanded, but all later ASCII documentation -including the MSX Datapack- defines it as slot address of the BIOS/MAIN ROM. Regards, Bernard Lamers -- For info, see http://www.stack.nl/~wynke/MSX/listinfo.html
