Aztecs & Time Detectives

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ARandomDave
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Aztecs & Time Detectives

Post by ARandomDave » Sun Apr 14, 2019 3:22 pm

Hi all,

Recently I've been lusting after playing two educational games I remember playing in an IT lesson some years ago, "Aztecs" and "Time Detectives - The Victorians" by Sherston Software.

I managed to find a demo for Aztecs and was disappointed when it ended. I've been keeping my eye out on eBay (despite prices..) but haven't seen either pop up. Its sad really, as I'm sure so many copies were thrown in the bin when they were ripped out and replaced with Windows machines.

Thanks in advance!

Edit 2019-10-27: Victorians now working, just after Aztecs now.
Last edited by ARandomDave on Sun Oct 27, 2019 4:50 pm, edited 1 time in total.

ARandomDave
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Re: Aztecs & Time Detectives

Post by ARandomDave » Sun Jul 28, 2019 4:01 pm

After much waiting, I have been able to source "Time Detectives - The Victorians" - complete with all literature from eBay.

Even better, I have been able to image the disks using fluxengine, with the exception of one sector on disk 1 - the key disk. Application and fonts installed just fine, but the program wont load - reporting "Please put the Victorians startup disc in drive 0". fluxengine copies the data anyway, where it can, ignoring things like the CRC check.

Has anyone got any suggestions as to how to get this running in RPCEmu? - I've spent ages trying to get to this point and any help would be greatly received.
Last edited by ARandomDave on Sun Jul 28, 2019 6:51 pm, edited 1 time in total.

ARandomDave
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Re: Aztecs & Time Detectives

Post by ARandomDave » Sat Aug 17, 2019 2:10 pm

*bump*

If I uploaded the disk images somewhere, would someone mind trying them with a physical Acorn to determine if the images themselves are good (and perhaps it's just the emulation later)

Thanks in advance

ARandomDave
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Re: Aztecs & Time Detectives

Post by ARandomDave » Sun Nov 10, 2019 3:33 pm

After managing to successfully bypass the protection in "Time Detectives - The Victorians", I thought I'd have a go at circumventing the protections in ArcVenture and ArcVenture IV. Sadly, both used more comprehensive protection checks. However, armed with !DDT and !Zap I was eventually able to bypass the checks in both

ArcV I implements its protection in a standalone module (ShAlloc) and opens cleanly in !Zap allowing two calls to XADFS_DiscOp to be bypassed without the need for decent debugging tools. If you're looking to do the same the change I used is as follows:

Code: Select all

00000208 BL &00000178
Image


ArcV IV was significantly more complex. The protection is implemented in the main !RunImage binary, which itself is compressed with squeeze (compression version 4.00). After trying several tools to decompress, I was eventually able to unsqueeze using http://ftp.uni-stuttgart.de/pub/systems ... queeze.spk. This left me with a ~170KB binary file (this felt monstrous to step through).

After locating a close-enough relevant instruction at 0002f168 (adr r1, &0002f198 ; = "Please place the %s startup disk in drive 0"), I spent some time single-stepping through to identify where the call was taking place. This was made more painful by !DDT crashing fairly frequently. If you're looking to do this too, the change is as follows:

Code: Select all

0002F178	BL	&0002F184
Image

(You'll need to have the "Resources" disc in drive 0 to play still, but the protection mechanism wont complain about the startup disc).

If anyone can source me Aztecs I'd be certainly appreciate it and happy to have a go at circumventing the protections.

If what I've posted above breaks any rules, then my apologies - happy to amend the post.

OutlawMedalist
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Re: Aztecs & Time Detectives

Post by OutlawMedalist » Sun Dec 15, 2019 12:58 pm

Hey, is there any way you could send me the files for Time Detectives?

I remember playing it a bunch as a kid when I was at school but never finished it. I've been looking for it on and off for about a year or so now.

ARandomDave
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Re: Aztecs & Time Detectives

Post by ARandomDave » Thu Dec 19, 2019 7:54 pm

OutlawMedalist wrote:
Sun Dec 15, 2019 12:58 pm
Hey, is there any way you could send me the files for Time Detectives?
Get in touch and we can work out the details.

ARandomDave
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Re: Aztecs & Time Detectives

Post by ARandomDave » Thu Dec 19, 2019 7:56 pm

ArcVenture 1 through 4 are all now patched to bypass protection and back with the author for release. For completeness, the changes to bypass the protections are described below.

ArcVenture II
Image
For ArcVenture II, the protection check occurs in !AV2Start's "!RunImage" First, decompress the image using "UNSQUEEZE" and then modify the instruction at 0x81A0:

Code: Select all

  From 000081A0 BL &0000D84C
  To 000081A0 BL &000081A4
If the instruction doesn't match the above, be sure the unsqueeze completed successfully. Optionally, then re-squeeze the file again and put it back on the disk.

ArcVenture III
Image
The protection occurs in !AV3's !Runimage. First locate the DEFNpalset function (basic line 4314) then make the following changes:

On BASIC line 4316, change EQUD &EB000029: to EQUD &EB000025:
On BASIC line 4317, change EQUD &EB000025: to EQUD &EB000021:

Sadly, the copy of Aztecs that the CCH has is in poor condition. Two files on disk 2 are corrupt (TWO.map and TWO.guard). Disk 3 has corruption across multiple files. If anyone can provide disk 2/3 I'll gladly share how to bypass the protections for use in RPCEmu etc.

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