[Coco] CoCo 3 MMU test for all
mark at cloud9tech.com
Sun Jan 20 20:43:00 EST 2008
You must be still sleep deprived or you don't understand the GIME.
I always thought programmers did it in hex? I know hardware designers do!
Per your table below. You can't look at it that way. Bits 6/7 ARE NOT
READABLE. That is why you AND out bits6/7.
128k: 112-127 s/b 0-$0f
512k: 64-127 s/b 0-$3f
1 meg: 64-255 s/b 0-$7f
2 meg: 0-255 s/b 0-$ff (only one you got right, think hex, it is easier)
Use the source Luke! CC3 Technical manual.
There is no gathering, it is how I described. Not sure how P-3 ever
worked based upon your table. You must have forgotten or wild things
will happen with the P-3 on systems larger than 512k.
I still follow Tandy's design guidelines. The SB is going to violate
a few of the rules but then Tandy isn't making the CoCo anymore. So I
don't have anything to worry about. I know the internal workings of
the CoCo, period. Spent many hours writing test code and watching how
the machine responds. There is A LOT of info missing or very vague in
the CC3 tech manual. Emulators are great but still don't beat the
real thing. Hard to create/test when one doesn't own a real CoCo3.
Reread my original post.
At 1/20/2008 07:06 PM, you wrote:
>At 03:49 PM 1/20/2008, you wrote:
>>I haven't been following this that close because it is something I
>>As james has indicated, basic CoCo understanding of the CoCo's
>>internal registers. A stock MMU is only 6 bits wide. 'AND' off the
>>upper two bits, bit6 & bit7.
>>Go to a 1 meg machine and bit0-6 will be used.
>>Go to a 2meg machine and bit0-7 will be used.
>>256 blocks of 8k sized blocks = 2megs.
>At least one of my comments were "sleep deprived"
>comments. ;) I've written programs like P-3 that take advantage of
>the full 512k memory map in a tricky way but using apparent blocks
>0-63. If 64 is added by the GIME for 128-512k CoCo's then I suppose
>it really means blocks 64-127 for 512k, and 112-127 for 128k even if
>you poke 0-63, while 1 meg upgrades *may* set the highest bit 7 by
>default to give the same behavior to push the blocks upward in the
>If so, what is now apparent for the actual hardware block #'s
>(regardless of what a PEEK reveals at the prompt for an MMU register
>for 128k-512k CoCo's):
>1 meg: 64-255
>2 meg: 0-255
>Somebody will correct me if I'm wrong, but this is what I'm
>gathering. For a stock CoCo 3, blocks are referenced as 48-63, though.
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