My A1200 2B

Jumping Anaconda

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I have opened up my A1200 quite a lot recently, but I keep on forgetting to check what the revision number is. I checked it today and was suprised to find that it was a revision 2B. The machine was purchased in the third month of release, early December 1992, marked as a UK produced unit, and arrived before retailers even had the 'Desktop Dynamite' pack. Does the same higgledy piggledy allocation of new and older parts that applied to the A500 series apply to the A1200? And were the 2B boards in circulation right from the initial release? And is 2B necessarily a progression from other numbered boards, or just a variant?

I have to admit that I have never been particularly happy with my A1200. I never found it to be that reliable, and the power supply that came with it was pathetic. While my A500 would crash every now and then, I always felt there were software reasons for this. With my A1200 I always felt there were underlying hardware issues that caused problems on top of the usual software issues. It was not until I picked up chunkier A500 power supply (I think one of the earliest ones that reuse a Commodore 128 power supply case?) that the machine really seemed to run stable at all. And by that time I had moved on to PCs.
 

tom2215

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Yeah, the 1200 power supplies were grossly underpowered, how could you expect to run a system with more powerful processors and a hard drive with a power supply of 25 watts? The amiga 500 had a 50watt power suppy and that's a weaker machine! I think there were some problems with the rev 2b board, bus timings or something. :dry:
 

Jumping Anaconda

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If I had known that about 2B's when I got it, I would have sent it back and asked for a replacement. I had so much trouble trying to do school work with that machine. I remember that Wordsworth had real problems with it.

An acquaintance of mine had trouble with his A1500. It never worked right from when he bought it, and it ended up going back to Commodore. In the end Commodore had it for about a year and never managed to send it back. In the end he wrote in frustration directly to David Pleasance, and a couple of days later a brand new A4000 turned up at his front door.
 

matt020

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Rev 2B is a progression. Modifications were made for the board to be ready for new version of the AGA custom chips, but those chips were never released.

The board works fine in stock form, but if adding an 040 or above CPU, "timing mods" need to be applied to the board.
 

Jumping Anaconda

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Like I said, early December 1992. I am guessing that they produced a run of 2B's expecting the corrected chips to be available, which they were not, and then they switched back to the 1D1. Seeing as they were running short of machiens for the Christmas 1992 period, maybe they dipped into 2B stock in order to meet demand?

I guess that Escom assumed that the 2B was the best available revision, and went with that. I would not be suprised if the 2Bs were either the first or second version to actually go into production.
 

Zetr0

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@Jumpy

Revsion 2B was out before the 'D' motherboards there is another version before the 2B but I cannot remember its designation at the moment. there was a few A1200 motherboards (not marketed) that only have 1MB of chip, not sure of that revision number either, but I know of thier existence.

the 2B by Commodore and the 2B by Escom are slightly different as Escom butchered the floppy drive controller to work with PC drives. (its all about the RDY signal)

have a look here are Ian Steadmans site, it gives you all the info you need to correct your A1200 version, I do beg that you make sure you know WHICH version of 2B you have and to ensure that if you are not sure, ask =D
 

Jumping Anaconda

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Thanks for the link, but there is no way I'll be carrying out any modifications to my A1200. I can't even manage to get my soldering on my guitar leads to last! I doubt I could even see those pins.
 

matt020

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I do beg that you make sure you know WHICH version of 2B you have and to ensure that if you are not sure, ask =D

Ok, Im askin' !

How do we determine which version of 2B we have?
 

matt020

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Ok. May I please have the name of a game (or demo) that uses a non-standard boot block so I can test my 2B?

Cheers
Matt.
 

TheCorfiot

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Matt

If it's an original A1200, ie not rebuilt from various sources then you can easily identify Escom 1200's by the Metal badge on the case.

If you have a look at BBoAH or Amiga resource you will find loads of piccys with both badges..

TC :)
 

Jumping Anaconda

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Well I know that mine is not an Escom board as I got mine in December 1992, several years before they bought the rights. But it is useful information for anybody else thinking about carrying out the hack.
 
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