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Old 12-02-2012, 02:42 AM   #1
Lord Aga
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Default A500 512KB Chip VS A500 1MB Chip

Are there any compatibility issues ?
Are there some games which would expect 512KB Chip RAM and then crash if they find 1MB Chip RAM ?

Both machines would have 8MB of fast RAM.
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Old 12-02-2012, 03:42 AM   #2
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Default Re: A500 512KB Chip VS A500 1MB Chip

If required you can add a switch to each the A19 jumper and the _EXRAM line to switch between both modes. I've very rarely used that switch if ever.
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Old 12-02-2012, 11:01 AM   #3
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Default Re: A500 512KB Chip VS A500 1MB Chip

Not sure if I follow...
I have a classic 512KB Chip RAM A500 (+512 Fast, but that's irrelevant). Now I have the opportunity to exchange the 512KB Agnus with a 1MB one.
Would that change somehow cause some incompatibility ? Is there a piece of software that is 512KB Chip RAM specific, and would crash if it finds 1MB of Chip RAM ? Or is that impossible ?
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Old 12-02-2012, 11:15 AM   #4
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Default Re: A500 512KB Chip VS A500 1MB Chip

Just changing to a your Agnus doesn't give you more chip RAM. It gives you the "ability" to have 1M.
You still have to add the other 512k TO chip.
That's usually done by modifying your MB a bit so that the 512k FAST you have in the belly becomes 512k more of CHIP.

I'm not sure if he's saying that that hack would let you toggle between the 2 configs or not? (sounds like it)

There are a FEW games that don't like more than 512k chip. Dragon's of Flame comes to mind....
But they are very very early games and generally not the good ones. ;-)
Also, there is a program called Degrader that lets you disable the extra 512K CHIP if you really want to play them. (Or if his hack works; I have extra CHIP, but haven't tried the above mentioned hack to the A19 jumper)

The bigger compatibility hit for older games is with kickstart upgrades.

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Old 12-02-2012, 11:23 AM   #5
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Default Re: A500 512KB Chip VS A500 1MB Chip

Here is how to do it rev 6 mobo

http://s2.postimage.org/8o0x83w69/A500_6a_1_MBCHIP.png

With this, you can use you slot expansion memory as a chip ram. You can also solder memory chips to directly to mobo

You have 8mb fast? Do you have harddrive controller?? If so you should use whdload
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Old 12-02-2012, 11:25 AM   #6
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Default Re: A500 512KB Chip VS A500 1MB Chip

Mhm, so this "IC 8372A, 1MB Agnus" isn't actually a 1MB upgrade. It is just a chip with a possibility to adress 1MB which must be obtained through further modification

@utri007
I don't have the 8MB fast yet. I was planning on buying kipper2k's 8MB fast + IDE combo upgrade for this A500.
But maybe I should leave this A500 intact for super compatibility, and just get an A500+ for whdload, as it was my plan all along
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Last edited by Lord Aga; 12-02-2012 at 11:32 AM..
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Old 12-02-2012, 11:40 AM   #7
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Default Re: A500 512KB Chip VS A500 1MB Chip

Most "ECS" game incompatibility I experienced were due to kickstart 2.04.

Last edited by alexh; 12-02-2012 at 11:42 AM..
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Old 12-02-2012, 02:05 PM   #8
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Default Re: A500 512KB Chip VS A500 1MB Chip

To change a 512/512 KB machine to 1 MB chip you need
- 1 MB Agnus
- change the A19 jumper to map the 2nd 512 KB to $080000 (instead of $C00000)
- cut the _EXRAM trace or jumper to disable the $C00000 RAM

The 1 MB Agnus by itself doesn't cause any incompatibility issues.
Some (extremely few) programs get confused by 1 MB chip RAM. For those you can add a switch to the A19 line (JP2 jumper) to switch between both jumper positions. $C00000 pseudo fast RAM will only be present if _EXRAM is active (usually closed by the trapdoor board), so you need a 2nd switch or a dual contact one.
Just don't set Agnus A19 to CPU A19 and activate _EXRAM at the same time - the machine will crash on boot-up. Also note that if you switch the A19 line while powered up the system will crash violently.

Last edited by Zac67; 12-02-2012 at 02:12 PM..
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Old 12-02-2012, 02:18 PM   #9
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Default Re: A500 512KB Chip VS A500 1MB Chip

Yup, everything perfectly clear now. Thank you
I don't think I'll be doing this. I'll go for an A500+ instead.
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Old 12-02-2012, 02:34 PM   #10
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Default Re: A500 512KB Chip VS A500 1MB Chip

Quote:
Originally Posted by Lord Aga View Post
Are there any compatibility issues ?
Are there some games which would expect 512KB Chip RAM and then crash if they find 1MB Chip RAM ?

Both machines would have 8MB of fast RAM.
of the very few that exist you can probably find a patched or whdload version of the game that will run...

I don't recall ever needing to set my minimig 1.1's chip ram to 512k. 1MB on a few things.

Last edited by bbond007; 12-02-2012 at 02:39 PM..
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Old 12-02-2012, 02:39 PM   #11
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Default Re: A500 512KB Chip VS A500 1MB Chip

Quote:
Originally Posted by Lord Aga View Post
I don't think I'll be doing this. I'll go for an A500+ instead.
If you can get an A500+, that's great.
But the mod is super easy.
I even did it. ;-) (Not with the switch, but just adding the 512k as CHIP.)

Good luck either way.

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Old 12-06-2012, 07:55 AM   #12
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Default Re: A500 512KB Chip VS A500 1MB Chip

That sucks. This whole time I thought my Amiga 500 had 1mb "chipram". Guess I have to do the damn hack.

Last edited by barney; 12-06-2012 at 07:59 AM..
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Old 12-06-2012, 12:46 PM   #13
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Default Re: A500 512KB Chip VS A500 1MB Chip

Quote:
Originally Posted by barney View Post
This whole time I thought my Amiga 500 had 1mb "chipram".
What causes your doubt?
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Old 12-06-2012, 06:32 PM   #14
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Default Re: A500 512KB Chip VS A500 1MB Chip

Quote:
Originally Posted by Zac67 View Post
What causes your doubt?
The reason I have doubt is because if the hack is absolutely necessary and I never did it yet, then I likely don't have 1mb chip Ram.
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Old 12-06-2012, 07:26 PM   #15
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Default Re: A500 512KB Chip VS A500 1MB Chip

Quote:
Originally Posted by barney View Post
The reason I have doubt is because if the hack is absolutely necessary and I never did it yet, then I likely don't have 1mb chip Ram.
Open up a SHELL and type "avail" to see.

Very few A500's came with 1M CHIP. The A500+ did, although I think some very early ones were 512k CHIP.

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