Memwatch not working for dff088

[kamelito]

I set a watchpoint like this w 1 dff088 2 all using an A500 config 1.3 KS launched a game and it is not trapped and stop what am I missing ?

[roondar]

Are you sure the game actually uses COP1JMP?

While many programs will explicitly strobe COP1JMP to (re)start the Copperlist at the pointer in COP1LCH & COP1LCL, this is not actually necessary. When Copper DMA is active, the Copper will automatically jump to the pointer contained in COP1LCH/COP1LCL at the start of each vertical blank.

So, it is possible that the game you're trying to analyse does not strobe COP1JMP, which would mean the watchpoint will never trigger.

[Galahad/FLT]

Maybe WinUAE gets confused because doesn't writing to $dff088 trigger a READ first then a WRITE?

[jotd]

it should work, unless the copper itself writes to this register. watchpoints only watch writes from CPU.

- ensure JIT is off
- make a simple test where you write into the register with the CPU, see what happens

[Toni Wilen]

Watchpoints can also watch DMA channels or reads only or writes only. Default is CPU only + RWI (any CPU access, including instruction prefetch).

Append "all" to enable all modes. (or "cop" for copper only, "blt" for blitter only, "blta" for blitter A only etc)

[Rock'n Roll]

memwatch works fine (CPU only is the default)
tested: w 1 dff088 2 also w 1 dff088 2 W
>w 1 dff088 2 W
1: 00DFF088 - 00DFF089 (2) W CPU
Memwatch 1: break at 00DFF088.W W 000028F6 PC=00022D28 CPUDW (000)

1. also COP memwatch should work:
>w 1 dff000 200 COP
1: 00DFF000 - 00DFF1FF (512) RWI COP

But how to find the copper instruction, what causes the break?
>g
Memwatch 1: break at 00DFF094.W W 000000D0 PC=00FC0F90 COP (08c)
VPOS: 043 ($02b) HPOS: 115 ($073) COP: $0001edc2
; it's dc.w $94,$d0

>o 1edc2 1
*0001edc2: 0000 010a ; BLTDDAT := 0x010a

2. and what makes a memwatch DMA validator?
>wl
Memwatch DMA validator enabled
>wlo
Memwatch DMA validator disabled

[jotd]

I learned something, didn't know that you could break with blitter or copper. Very useful!!

Someone should create a proper doc for debug one of those days. So many unknown yet useful features!

[kamelito]

True

[kamelito]

Originally Posted by Toni Wilen

Watchpoints can also watch DMA channels or reads only or writes only. Default is CPU only + RWI (any CPU access, including instruction prefetch).

Append "all" to enable all modes. (or "cop" for copper only, "blt" for blitter only, "blta" for blitter A only etc)

This mean it should always be triggered. I will check JIT.