Date   : Wed, 30 Jul 2008 12:14:49 +0100
From   : info@... (Sprow)
Subject: ROM type byte for PDP-11

In article <080728205504@...>,
   Jonathan Graham Harston <jgh@...> wrote:
> I have a requirement to specify PDP-11 code in the ROM type
> byte at rombase+6.

[snip]

> Any comments? Ta.

On the basis of the "ROM type byte inconsitancies" thread it seems a number
of clients AND with 13, so

         0 & 2=>  0
         1 & 3=>  1
         4 & 6=>  4
         5 & 7=>  5
         8 & 10=> 8
         9 & 11=> 9
        12 & 14=> 12
        13 & 15=> 13

I can imagine that the 6502 clients (6502, Turbo, !65Tube) did this as a
quick method of checking for 0-3 where presumably bit 0 set meant Turbo?
That would be consistent with the comment

In article <080708085502@...> wrote:
> Also, even though all documentation says x3 is 68000, the 65Tube
> client code recognises that as Turbo6502.

Then subsequent clients were derived by giving someone the 6502 source code
as a basis and they merrily translated it faithfully without realising the
deviousness of the origin of AND with 13.

That gives
              AND13   What            Aliases with
         0=>  0       6502 BASIC
         1=>  1       Turbo
         2=>  0       6502
         3=>  1       Turbo again     68000/6809?
         4=>  4       Free
         5=>  5       Free
         6=>  4       Free
         7=>  5       Free
         8=>  8       Z80
         9=>  9       32016
        10=>  8       Free            Z80 due to AND error
        11=>  9       80186           32016 due to AND error
        12=>  12      80286
        13=>  13      ARM
        14=>  12      Free
        15=>  13      Free

I propose:
That 68000/6809 (neither of which I've seen) was an assignment error - tough.

The Z80 2.00 client could be patched to free up number 10, but otherwise it
must be set aside, the 1.xx client was plain broken accepting 8-15.

The 32016 client could be patched so it doesn't clash with 80186, though
there were probably more 80186's made no one seems to have seen any language
ROMs for them so it's a little moot. 

This leaves 4-7 and 14-15 genuinely free, flip a coin?
Sprow.