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Old 17 August 2018, 09:59   #1
Sim085
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How to know if A500 is OCS or ECS?

Hello, I know that the A500+ is ECS. However when it comes to the A500 how can one determine if it is an OCS or ECS? Wikipedia says: "Amigas produced from 1990 onwards featured a mix of OCS and ECS chips, such as later versions of the Amiga 500". Can one determine this from the hardware, for example assume all rev 6A are ECS? Or this is something to be done through software only?
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Old 17 August 2018, 10:12   #2
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I have a spare 6A and its ECS Agnus. But there is reception for 1mb Chip. You have to look at the motherboard I guess. Or use some utility? The A500+ is rev. 8-something.
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Old 17 August 2018, 10:27   #3
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You can use software to determine your Agnus and Denise versions. Or crack it open and see. It is not very easy to be sure without booting it up or opening it.

1MB and 2MB Agnuses are ECS, Super Denise is ECS.

The only rough guide I can give is, that most A500s that shipped with a green power LED from the factory are half ECS, meaning a 1MB Agnus with the original Denise.
Another way of determining a half ECS machine: If the power LED goes dim instead of off, it may have a 1MB Agnus from the factory, standard Denise.
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Old 17 August 2018, 11:26   #4
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So if an A500 comes with 512bytes of chip ram and takes another 512 bytes from expansion port then it is ECS (since Agnus must support 1MB)?



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You can use software to determine your Agnus and Denise versions. Or crack it open and see. It is not very easy to be sure without booting it up or opening it.

1MB and 2MB Agnuses are ECS, Super Denise is ECS.

The only rough guide I can give is, that most A500s that shipped with a green power LED from the factory are half ECS, meaning a 1MB Agnus with the original Denise.
Another way of determining a half ECS machine: If the power LED goes dim instead of off, it may have a 1MB Agnus from the factory, standard Denise.
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Old 17 August 2018, 11:30   #5
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Quote:
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So if an A500 comes with 512bytes of chip ram and takes another 512 bytes from expansion port then it is ECS (since Agnus must support 1MB)?
Well, if the second 512KB is *Chip* RAM, then it's an ECS Agnus. On the A500 as standard it's mapped as slow-fast RAM, regardless of Agnus version, so that alone isn't a reliable way to tell.
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Old 17 August 2018, 11:41   #6
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Running WhichAmiga shows which chips are ECS:


Edit: I think that all Rev 6 are partial ECS and rev. 8 are likely full ECS (500+ spec). You won't find many full OCS machines any longer since they need to be the very first ones which usually had red power LEDs that turned off completely instead of becoming dimmed and were shipped with KS1.2.

Last edited by demolition; 17 August 2018 at 11:48.
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Old 17 August 2018, 12:42   #7
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I have a 5a/6a (can't remember which) with a red LED. Some of these machines are pieced together from whatever is lying around - i dont think you can really tell by looking from the outside. (reliably anyway).

Oh, i should add that I was the first to ever open it. (Which felt like opening lost treasure, i might add)
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Old 17 August 2018, 12:42   #8
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Quote:
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So if an A500 comes with 512bytes of chip ram and takes another 512 bytes from expansion port then it is ECS (since Agnus must support 1MB)?
This is an incorrect conclusion. Any Agnus can be configured to have 512k Chip/512k Slow. Rev 6 A500s all shipped like this from the factory, no matter whether they had the 512k OCS Agnus (rare) or the 1MB ECS Agnus.

The memory size here is in reference to the maximum Chip configuration that particular Agnus will support. If you have a 1MB Agnus, you can reconfigure it to have 1MB of contiguous Chip.

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Running WhichAmiga shows which chips are ECS:


Edit: I think that all Rev 6 are partial ECS and rev. 8 are likely full ECS (500+ spec). You won't find many full OCS machines any longer since they need to be the very first ones which usually had red power LEDs that turned off completely instead of becoming dimmed and were shipped with KS1.2.
Machines shipped with 1.2 are all full OCS, but there are also KS1.3 Rev 5 machines, full OCS + LED that goes dark.

It's quite difficult to determine this without looking at the chip or using a piece of software. These machines have come through many hands and many have been upgraded / repaired over the years.
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Old 17 August 2018, 13:44   #9
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Ok, mine are all have 1.3 kickstart. When I add 512kb ram expansion I don't get any fast ram reported, all is reported as chipRAM from Workbench 1.3. Would this mean that all ram is being recognised as chipRAM? (I am asking mostly out of curiosity as I never experiences slowRAM).

I will try whichamiga to get a definitive answer re ECS.
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Old 17 August 2018, 13:53   #10
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Quote:
Originally Posted by project23 View Post
I have a 5a/6a (can't remember which) with a red LED. Some of these machines are pieced together from whatever is lying around - i dont think you can really tell by looking from the outside. (reliably anyway).

Oh, i should add that I was the first to ever open it. (Which felt like opening lost treasure, i might add)
Indeed, I recently broke the seal on an A500 that had red power and caps lock LEDs and a totally different feeling keyboard to most A500s, but was mildly disappointed to find a standard Rev. 6A board inside.
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Old 17 August 2018, 13:59   #11
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Indeed, I recently broke the seal on an A500 that had red power and caps lock LEDs and a totally different feeling keyboard to most A500s, but was mildly disappointed to find a standard Rev. 6A board inside.
Whats the serial number? I'll check mine when I get home later on...

I wonder if they're closely batched, as i'm sure mine is a 6a and like you has the red caps lock LED as well.

I wasn't disappointed though - i'd gotten it for just 20 pounds a couple of months ago, and the absolutely immaculate interior of a never before opened 500 really put a smile on my face.

I think most of the chips in mine are 88/89 vintage?

John

EDIT: Should see the state of the 512k expansion board though... Talk about battery corrosion - even the ceramic caps had big holes in them. I'm currently working on it as a side project to see if i can restore it to working order. I was pretty lucky that none of the corrosion spread to the 500 itself.

Last edited by project23; 17 August 2018 at 14:08.
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Old 17 August 2018, 14:28   #12
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It wasn't my machine, I was doing some work on it for someone else but I'll find out the serial number. Sounds like they could be similar alright. I was only disappointed because I thought it might be a Rev. 3 board (which I've never before seen in the flesh), but was still nice to see such a pristine board.

Yeah, often it seems that the storage conditions (standing on the floppy end or front keyboard end) can be the difference in protecting the mainboard from corrosion from leaky expansions. Looks like you were lucky indeed
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Old 17 August 2018, 15:19   #13
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Could you not just check the new display resolutions with the right Workbench disk?
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Old 17 August 2018, 15:53   #14
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With 1.3 ROMs your best choice is to use Sysinfo to view the custom chip revisions, as the ECS Denise resolutions are not available under 1.3.
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Old 18 August 2018, 03:10   #15
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Surely there is some Amiga BASIC/AREXX code which you can type that peeks and pokes an adress to get the chipset value?
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Old 18 August 2018, 08:44   #16
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At least in AmigaBASIC it is possible to peek the registers.
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Old 18 August 2018, 15:55   #17
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Mine is half and half. It has the ECS 8372A Agnus chip but the regular OCS Denise.
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Old 19 August 2018, 05:25   #18
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Quote:
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At least in AmigaBASIC it is possible to peek the registers.
You can also read memory address's like $4 ExecBASE in AREXX???
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