31 replies to this topic

[DarkLord]

ParanoidLittleMan, on Wed Mar 14, 2012 9:51 AM, said:

I just checked Blood Money (upped by DarkLord, I guess) - it works fine with USB HxC and STE. So, DarkLord, your effort was not for nothing :-)

Coolness! I uploaded 5 titles, I'll try to do that whenever I'm off work, at least until I've uploaded everything
that I do have that matches their list.

[CyranoJ]

ParanoidLittleMan, on Wed Mar 14, 2012 9:51 AM, said:

In any case, tracing on real ST(E) may help in finding what is exact point when fails on Steem. I will try with Blood Money, when will have some time.

We already did this, over 4 years ago, with Ijor.

You really do like re-inventing the wheel. Who knows, when you find out why it doesn't work (again) maybe you can take credit for it?

[ParanoidLittleMan]

And how I should know about it, when no info about it - googleable for instance.
Then, we now have Steem sources, so possibility to fix errors.
Fixing Steem bugs with Address/Bus error emulation will be not easy. And that's the point.
Considering Warp - tricky code jumps in PSG address space, and it is not correctly emulated too.
I guess that posting those few not working in emus STX images will not overload AM

[ijor]

Warp executes code from HW I/O space. This is specifically not supported by Steem. The same "protection" affects one or two other titles. There is (at least) one more bug in Steem, inaccurate CPU emulation, that prevents Warp to run.

Blood Money exposes two slightly different Steem bugs related to wrong handling of bus and address error exceptions.

[Bryan]

ijor, on Mon Mar 19, 2012 8:36 AM, said:

Warp executes code from HW I/O space. This is specifically not supported by Steem. The same "protection" affects one or two other titles. There is (at least) one more bug in Steem, inaccurate CPU emulation, that prevents Warp to run.

How on earth do you do that? And what protection does it really offer (other than emulator protection)? Do you just try to set up the read values so it jumps right back out?

[ParanoidLittleMan]

ijor, on Mon Mar 19, 2012 8:36 AM, said:

Warp executes code from HW I/O space. This is specifically not supported by Steem. The same "protection" affects one or two other titles. There is (at least) one more bug in Steem, inaccurate CPU emulation, that prevents Warp to run.

Blood Money exposes two slightly different Steem bugs related to wrong handling of bus and address error exceptions.

Right.
Here is what I found so far:  Warp  writes $60 to PSG reg. Then jumps there ($FF8800) . On real HW then $60FF executes, what makes address error .
In Steem it executes $6060 and jumps, but then makes address or bus error (don't remember at moment which exactly). But address/bus error is not perfect emulated.
So, at least 2 errors.


Blood Money:  first error is by  jsr (a6) with odd a6. Address error has 2x PC on top of stack instead 1 .  Additionally FC bits on stack bottom by address/bus error are not correct always.
Then comes bus error when code writes to $400000 - similar errors in emulation.
I set correct values on stack, according to tests on real STE. And reached loading of third sector, but it loads likely in wrong area .  Maybe because some bad value still on stack, maybe there is some DMA emul. problem too ?
It seems that FC (function code) bits are not well emulated in Steem. What may be biggest problem in all this.

I don't think that intention of programmers was to prevent running in emulators (which did not exist around 1990). But to confuse crackers, tracing SW.

[ParanoidLittleMan]

OK, here is another case of game not working in emulators, but this time with solution and explanation too.
http://atari.8bitchi...GA/M/mpgolf.php
There may DL STX images with patches for Steem, MSA images of deprotected and patched for emulators + hard disk installable (HAGA version soon).
The problem with emulators is not perfect MFP emulation - Steem, Saint, Hatari  -  all crash during intro.