On Fri, 10 Aug 2001, Armin F. Gnosa wrote: > That sounds like an interesting alternative to pulling the PROM out of > its socket. Then, a program running on a DECStation 5000/200 should be > reading from 0x1F81C0000..0x1F1FFFFF, right? One question about Byte > Merging: Does it mean that I don't have to read bytewise but instead > DWORD-wise? The system ROM is mapped from 0x1f800000 up to 0x1f83fffff (and repeated at 0x1fc00000) and is 256kB in size on my /240. Although I cannot verify it, docs state that the /200 contains the following ROMs: - the system ROM from 0x1fc00000 up to 0x1fc7ffff (repeated at 0x1ff80000), 256kB in size, - the PMAD-A ROM from 0x1f9c0000 up to 0x1f9fffff, 32kB in size, - the PMAZ-A ROM from 0x1f4c0000 up to 0x1f4fffff, 32kB in size. The system ROMs are presented on the whole data bus, while the option ROMs are only presented on 8 least significant bits. The merging can be switched off for I/O ASIC systems (I haven't tested the exact behaviour of this configuration) but it seems to be hardwired for the /200. -- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
