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Re: Need a really good ram unit test program

On Thursday, April 19, 2012 9:32:34 PM UTC-7, BLuRry wrote:
> Not to test memory, but really what I need is the ability to test the behavior of the MMU and all the softswitches related to it.  I keep getting random crashes in JACE in games that use AUX memory, and sometimes Prodos as well.  Though it's speculative, I think the most prudent thing to do is assert what is proper MMU behavior with a software-based test and compare results to a running physical machine.  Since there are some switches (for LC) that require being accessed TWICE before they allow writes, these are the sorts of things that should be tested in all, or at least most, possible combination.
> 
> Specifically, I get the impression that aux ram is being switched back to main ram and the program counter is not picking up the right opcode at the right time, or from the right place.  But its only a hunch.  It could be a similar issue but with language card banks.
> 
> Before undertaking such a labor of pain.. er... love, I wanted to see if anyone knew of any good diagnostic programs that tested language card ram and aux ram -- I might get what I need from something off the shelf.  
> 
> Any advice or tips greatly appreciated!
> 
> -Brendan

Hi Brendan-

Can you isolate the failure to ether AUX RAM of LC RAM access?  The soft switches for AUX RAM are pretty straight forward.  When writing Appalm, Ultima IV gave me fits with its LC access (more from a performance standpoint than functionality).  It keeps its graphics assets in the second bank of the LC and ping-pongs constantly between the two banks.  I would think if you can run Ultima IV, your LC code should be pretty solid.

Sometimes writing a simple test to try out the combinations one at a time is useful.  I had to do this for the LC mode where LC RAM is write enabled, but reads from ROM.  ProDOS does some clever tricks to figure out how the LC is currently configured (no softswitches to read) before calling into the guts of ProDOS in the LC.

My second thought involves interrupts.  Is JACE emulating interrupts?  I have run into issues with the unenhanced IIe and interrupt interaction with AUX memory usage.

Sorry I don't have anything more formal.

Dave...