[game_preservation] Preservation of analogue game media

[Andrew Armstrong]

I'm interested in hearing more and how people can help. Responses on 
this mailing list widely vary, and there isn't as many institutions as 
I'd like to see involved here, we'll need to invite more people on :)

Andrew

Kieron Wilkinson wrote:

> I'm not sure how much interest there is in this, but I'll carry on 

> regardless. :)

>

> In my previous post, I summarised what I thought were the technical 

> challenges faces in preserving games stored on floppy disk media. I 

> them split those points into two categories, which I will now detail 

> further.

>

> a) Reading the disks in the first place

>  

> Getting hold of appropriate disk drives seems to be easy enough for 

> the majority of disk types, the problem is getting the raw data off 

> the disk. Floppy disks are an analogue storage medium, and data is not 

> directly stored as 0's and 1's like on Compact Discs and flash drives, 

> but as magnetic polarity changes ('flux transitions'). The problem is 

> that you cannot generally read these flux transitions through a 

> computer, as there is hardware in the way way to make accessing the 

> data "easier" (and did it's job well, but now is a problem for 

> preservation). This "raw" form is the ideal thing for preservation. 

> Once you have this, you don't care about disk formats or copy 

> protection - you are just doing a raw read of a disk - and it all 

> comes along for the ride.

>

> You might think that if the computer can read the data, there 

> shouldn't a problem. Unfortunately that is not the case, the only way 

> to get a computer to read particular things is to write it in a 

> special way on special hardware, a concept that underlies many copy 

> protection techniques.

>   

>  

> b) Knowing that what you have read is correct

>  

> Secondly, there is knowing whether the disk image you have made is 

> correct. There is little point of trying to preserve games if you 

> cannot be sure whether those disk images are okay or not. With most 

> types of storage media we use today, this is not a problem - the data 

> is checked as it is copied. But games on floppy disks are a special 

> case, you often do not know where the checksum/integrity information 

> is stored on the disk, and even for known disk formats, games 

> developers applied copy protection that deliberately wasn't covered by 

> the integrity data. The disks are old already, the data may already be 

> broken, and you won't know if you need to find another copy without 

> being confident in your disk images.

>  

> You cannot play the game to check it, the corruption may not be 

> apparent until, say, level 14. Also, how do you know the copy 

> protection passed? It is not always obvious. Borrowed Time on the 

> Commodore Amiga has very nice protection, if it fails, you can't find 

> some items to allow you to proceed in the game, they simply don't 

> appear - and that is not the only example.

>

> It gets worse, what if somebody modifies a game disk (virus, accident, 

> malicious intent, save games)? There will be no corruption, but it 

> certainly is no longer an authentic copy suitable for preservation.

>  

> I firmly believe that any disk images produced also require some sort 

> of checking to be confident in their preservation status. I'll drop a 

> small note here that The Software Preservation Society check for all 

> of above for every single game preserved (nearly 3000 so far).

>  

>

> I think all that covers the points raised in my last email.

>  

>  

> With these sorts of difficulties, it is no wonder that game 

> preservation (for computers at least) has historically been in such a 

> poor state. 

> In my next post, I will detail some new developments that I believe 

> makes the future brighter for everybody.

>  

> If anyone has any comments on any of this, please feel free to chime 

> in with your thoughts.

> Kieron

>

>

> On 13 Feb 2009, at 23:05, Kieron Wilkinson wrote:

>

>>  

>> Since I have been away for a while, I was trying to get a feel for 

>> how things have changed, and I thought this was a good place to 

>> start. I guess there doesn't seem to be many people here involved 

>> with that side of things, perhaps it is still very much an ad-hoc 

>> process.

>>  

>> As I said before, there does seem to be a number of common technical 

>> problems in preserving game media. Here are the ones I can think of:

>>  

>> 1) Devices required to read the disks

>> 2) The different and custom disk formats in use (I don't mean the 

>> physical disk format here, but how the software data is structured on 

>> the disk)

>> 3) The presence of any disk-based copy protection (the whole purpose 

>> of which is to hide itself)

>> 4) Degradation of original disks, leading to corrupted reads

>> 5) Authenticity (ensuring disks are original and unmodified)

>>  

>> I'd like to cover these points as two distinct problems...

>>  

>> a) Reading the disks in the first place (points 1, 2 and 3).

>> b) Knowing that what you have read is preservable (points 4 and 5, 

>> but also involves 2 and 3).

>>  

>> I don't want to go into too much detail in one post, so I will leave 

>> it at this for now, and follow up this two issues separately later.

>>  

>> If anyone has any comments on any of this, please feel free to chime 

>> in with your thoughts.

>> Kieron

>>

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