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Amiga computer related discussion => Amiga Gaming => Topic started by: Lord Aga on December 02, 2012, 09:42:20 AM
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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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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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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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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.
desiv
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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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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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Most "ECS" game incompatibility I experienced were due to kickstart 2.04.
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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. ;)
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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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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.
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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.
desiv
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That sucks. This whole time I thought my Amiga 500 had 1mb "chipram". Guess I have to do the damn hack.
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This whole time I thought my Amiga 500 had 1mb "chipram".
What causes your doubt?
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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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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.
desiv
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Very few A500's came with 1M CHIP.
I dunno if that is true. My "Flight of Fantasy" pack came set for 1M chip. Annoying when playing Lionheart
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1MB RAM was very common in New Zealand. Everyone I knew had at least that. Most of the packs that Commodore pushed had the 1MB as a selling point.
I remember drooling over a 2MB upgrade at the local PC store back in the day :-)
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I dunno if that is true. My "Flight of Fantasy" pack came set for 1M chip. Annoying when playing Lionheart
Not quite sure what that means.. :confused:
OH! I just re-read what I typed..
Duh!!
I know what you mean.. I was considering an A500 to be different from an A500+.
Even if you include the 500+ as an A500 tho, I still think very few A500's came with 1M CHIP.
Only near the end of life when they were stuffing a few A500+ motherboards in the A500 cases, as I understand it, and then the A500+'s.
I'm not saying it didn't happen. I didn't say that no A500's came with 1M CHIP. Just very few.
Of course, in that case, I'm assuming that very few of the total Amiga 500's that were sold were 500+'s.
desiv
(And by "very few" I mean in comparison to the Amiga 500's sold. It could well be many thousands. But compared to the (something over a million) 500's sold, I consider that very few.) I suppose I should have said a small percentage.
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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
Uh-Oh ! Cool ! Just what I was gonna google myself to. Thanks !
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Only near the end of life when they were stuffing a few A500+ motherboards in the A500 cases, as I understand it, and then the A500+'s.
I never heard of any revision 6 motherboards being shipped with 1mb of ram, even though they obviously designed it specifically for that. However it would conflict with memory in the trapdoor and they didn't include a clock on the motherboard. So I doubt they shipped any with the memory on board and I can't see them fitting a memory expansion to them.
The revision 8 in an a500 case was down to marketing as far as I can tell. For some reason they didn't launch the a500+ in some markets. It turned up in the UK early due to the last a500's being on a ship when demand stripped the supply in the run up to Christmas, all they ready were a500+'s that could be put on a plane. These did ship with 1mb of chip ram, and with kickstart 1.3. I wouldn't bother with an a500+ though, an a500 with trapdoor memory expansion is fine for floppy games. For anything else an a1200 is better.
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A - real - A500+ does support 2 MB chip ram though... ;)
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A - real - A500+ does support 2 MB chip ram though... ;)
You can get 2mb chip ram on an a500, but it's just not worth it.
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I suppose that depends..
It's not that difficult to get 2M CHIP on an A500. I have that.
The mod mentioned and a DKB miniMegaCHIP.
Wasn't that spendy...
But, is it worth it?
Interesting question.
If you're wanting to do more serious video/graphics or music/sound stuff, then yeah.
Those things can get CHIP hungry.
But for the average user? (Like me)...
Well, I'm glad I have a 2M CHIP A500. It was fun to get there, but I doubt I'll ever really use it....
Still, I got a decent deal on the DKB, so I think it was worth it. For the Amiga enthusiast in me... ;-)
desiv
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I was always under the assumption that if you installed the common 512kb expansion in the trap door, then you would then have 1mb chip ram.
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I was always under the assumption that if you installed the common 512kb expansion in the trap door, then you would then have 1mb chip ram.
Nope. Without A19 and _EXRAM being correct it's still $C00000 'slow' RAM.
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Nope. Without A19 and _EXRAM being correct it's still $C00000 'slow' RAM.
I've ended up selling my A1500, but that was setup for 1mb chip ram and loads of software refuses to run on it (it's kickstart 1.3).
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Not quite sure what that means.. :confused: I know what you mean.. I was considering an A500 to be different from an A500+.
Flight of Fantasy A500's were NOT A500+. They were half ECS A500's (ECS Agnus but regular Denise) and mine with a 512Kbyte trapdoor RAM was configured for 1Mbyte of Chip RAM.
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Flight of Fantasy A500's were NOT A500+. They were half ECS A500's (ECS Agnus but regular Denise) and mine with a 512Kbyte trapdoor RAM was configured for 1Mbyte of Chip RAM.
So, I wonder if those were some of the ones that were talked about where it was a 500+ MB in an A500 case?? I don't know enough about them to know whether motherboard revs are generally specific to 500+ or ?????
Otherwise, kind of weird that Commodore would bother to mod boards for 1M CHIP, but it is Commodore... ;-) :-)
I still think it's probably in the less common area, but that's just a guess.
desiv
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So, I wonder if those were some of the ones that were talked about where it was a 500+ MB in an A500 case?
Nope sorry. This was April 1990, over a year before the chipset for the A500+ was even invented. Months before the A3000 was launched.
I'm not sure there wasn't even an ECS denise at the time. Just this 1Mbyte Agnus.
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I know this is an old thread, but, if you are still around, can you provide a picture of this setup? I have already done the 1mb chip mod on my Rev6a board, but, want the ability to switch between 512k/512k configuration as you describe. I have a 512K expansion in the trapdoor port.
Would I use a switch like that in the link below?
https://www.adafruit.com/product/3220?gclid=EAIaIQobChMIjNaop8-K1gIVkrXACh1VLwIaEAQYAiABEgKPgvD_BwE
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. ;)
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@kirk_m
You need a DPDT switch (like the one you linked to).
DPDT = 1P [1T | 2T] + 2P [1T | 2T]
1P = pin 2 of JP2 then 1T = pin1 of JP2 and 2T = pin3 of JP2
2P = pin 2 of JP7A then 1T = pin1 of JP7A and 2T = unconnected
This way, the 1P1T + 2P1T setting will enable 512 chip + 512 ranger
and the 1P2T + 2P2T setting will enable 1 MB chip.
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Thanks! Do you know if such a switch setup will work if I have a megachip installed on this a500? Currently, I do, so there are really 2 megs of chip in there.
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Thanks! Do you know if such a switch setup will work if I have a megachip installed on this a500? Currently, I do, so there are really 2 megs of chip in there.
I don't, never tried it, but it doesn't hurt to try. You could even use a 3PDT switch, with the 3rd pole for the megachip wire to Gary.
DPDT = 1P [1T | 2T] + 2P [1T | 2T] + 3P [1T | 2T]
1P = pin 2 of JP2 then 1T = pin1 of JP2 and 2T = pin3 of JP2
2P = pin 2 of JP7A then 1T = pin1 of JP7A and 2T = unconnected
3P = wire from Megachip then 1T = unconnected and 2T = Gary pin36
This way, the 1P1T + 2P1T + 3P1T setting would supposedly enable 512 chip + 512 ranger (with the remaining 1 MB ignored)
and the 1P2T + 2P2T + 3P2T setting would enable the full 2 MB chip RAM.
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Before playing with hardware switches to undo the 1MB Chip mod (which was an official Commodore upgrade), try Degrader (http://aminet.net/package/util/misc/Degrader) for the very few programs that choke on 1MB+ of Chip RAM.
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Before playing with hardware switches to undo the 1MB Chip mod (which was an official Commodore upgrade), try Degrader (http://aminet.net/package/util/misc/Degrader) for the very few programs that choke on 1MB+ of Chip RAM.
+1
IMHO no reason to "degrade" any system in this way in 2017. But good luck with that, am kind of curious to know what will happen if you try it with the Megachip. I guess in theory you could set it to 2MB/1MB/512K. Interesting to try, I suppose? ;)
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Before playing with hardware switches to undo the 1MB Chip mod (which was an official Commodore upgrade)
Even though Commodore made the instructions available, and made a PCB revision tailor-made for the upgrade (6A/7), they also made it very clear that at least for the A500 it would not be a supported configuration.
On the other hand, 2 MB chip RAM on the rev6A A500 using the 8372B Agnus in its "natural" mode (single bank of four 1Mx4 chips) clearly had their blessings.
That said there's nothing wrong of course with the 1 MB chip RAM mod, Commodore not supporting it was just a marketing decision.
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Even though Commodore made the instructions available, and made a PCB revision tailor-made for the upgrade (6A/7), they also made it very clear that at least for the A500 it would not be a supported configuration.
On the other hand, 2 MB chip RAM on the rev6A A500 using the 8372B Agnus in its "natural" mode (single bank of four 1Mx4 chips) clearly had their blessings.
That said there's nothing wrong of course with the 1 MB chip RAM mod, Commodore not supporting it was just a marketing decision.
I suppose that depends on what the definition of "not supported" is. It was a *required* procedure in order to use the A570 and dealers would perform it under warranty.
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I guess so... but as far as shipments go, I don't think they ever shipped a 1 MB chip RAM configured A500. This held true all the way up to the last rev8A A500s which shipped with the trapdoor still configured for $C000000 'ranger' RAM.
There is mention of this "policy" somewhere but I can't seem to locate the document anymore :-(