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 +
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