On 04-Sep-18 14:14, Lars Brinkhoff wrote: > Phil Budne wrote: >> I seem to recall VAX boot ROMs handled by doing "load -r kaxxx.bin" >> How are VAX boot ROMs done? At _some_ point I thought it was done >> with "load -r". Is that not available in the PDP-11 simulation? > I randomly checked one of the VAX models. It seems memory is modeled > with at least two arrays: M[] for RAM, and a separate rom[]. Digging > further, I see there's also NVRAM and some other memory regions. The > PDP-11 doesn't have this. > The Unibus/QBus can have multiple ROMs. Besides the various M9301 variants (on the Unibus), the 11/34 ASCII console can be loaded as can the M9312, M792 & M873 variants, MRV11, etc. And the corresponding QBus console & boot ROMs. There are dozens (literally) of ROM variants for different combinations of devices & consoles. Not just from the -11 world - LCG created quite a few custom ROMs for PDP-11 based ANF-10 nodes & communications front ends.
If a ROM device is added to the -11, I suggest that: a) It be capable of multiple units b) each unit with a start address (in I/O space) & length c) the unit accept "attach <FILE>" to provide the code/data d) the existing gt40 hack that Mark described be migrated to use the ROM e) preferably, provision be made for the other functions of a ROM module, mentioned below. Some ROM modules respond to power failure by forcing the trap to 24/26 to use the ROM's address (e.g. power-on boot). These usually provide a pin that allows an external switch to force a bootstrap - this is used by the console ROMs and also by the KL10(DTE)/DL10 to allow the host to control an -11. (It's also used by DMC/DMR11s, but in a slightly different way). There's a M9312 tech manual on bitsavers... There's also a commented listing of that ROM - http://www.bitsavers.org/pdf/dec/unibus/K-SP-M9312-0-5_Aug78.pdf Bitsavers also has an M9301 tech manual. And some M9301 ROM dumps turned up at http://ana-3.lcs.mit.edu/~jnc/tech/pdp11/PDP-11_Stuff.html Attach will accept switches, so you can provide loaders for straight binary, ASCII (e.g. S-record or Intel Hex), or whatever else comes to mind. I'd start with straight binary (byte 0 of the file maps to ROM address +0). With this architecture, adding a boot (or device) ROM becomes as simple as distributing the ROM image. And SimH doesn't have to compile-in every ROM. And it would bring us closer to being able to handle PDP-11 host and network boot.
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