A500 to A500+ production transition and quirks

Jumping Anaconda

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I just noted the post in the thread about A1200 motherboards that suggested that there was no stock rotation on some of the Amiga 1200 production runs. Hence the motherboard in your machine may not be predicted by the year of production or purchase of your machine. It reminded me of a question I have meant to ask on here for a few weeks.

I can recall seeing an odd Amiga 500, maybe two, probably at the 1991 World of Amiga show. This was the show where I first saw the A500+, and one of the most striking things about the case was the shortened return key to make way for the extra key. The thing was, While I was there, I saw a machine on display promoting a product, which was labeled as a straight A500 and running 1.3, but it had the extra key. I think the label was more in the style of the A500+ label too. I can not remember why, but I think I have had a snoop around this machine and noticed it had 1meg chip, but no trapdoor expansion, suggesting that it could have the A500+ motherboard, just with a 1.3 rom and a new A500 label stuck on.

Does anybody know if this was a known variant of this machine? I would be really interested to see anybody has come across one. It really did seem very white (but not as white as the A1200 case).

My A500 was an ECS machine, but I think it had an older case, a lot darker than this A500, and I do not recall it having a model label at all.
 

AndyLandy

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The big C= did all kinds of weird stuff where the A500+ is concerned. The transition phase included A500 machines with ECS Agnus and OCS Denise, or vice-versa, with either KS1.3 or KS2.04. It was something to do with the A500+ not being properly released until 1992, but they were desperately short of A500 stock for the Christmas period, so sold A500+es as A500s.
 

Jumping Anaconda

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So there were A500s that went out with Kickstart 2.0 in them? I know for sure there was a lot of A500+ stock about at the World of Amiga show in 1991. Commodore must have really fouled up to be running short, especially as there were dealers carrying stock of A500's they had bought for Xmas retail I would have assumed was still being sold well into 1992.

I can remember there being 1.3 A500s still being sold after the A600 came out. And we know there was versions of the A600 that went out with Kickstarts that did not even support the internal ide interface or cardbus...

I wonder if any machines labeled as A500+'s got sent out with 1.3 in them? Or even better, 1.2 :)
 

MagerValp

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I can recall seeing an odd Amiga 500, maybe two, probably at the 1991 World of Amiga show. This was the show where I first saw the A500+, and one of the most striking things about the case was the shortened return key to make way for the extra key.

Are you talking about these two layouts?

http://openbytes.files.wordpress.com/2008/09/amiga500.jpg
http://image2.ac7.org/image/1097.jpeg

That's just the US layout (first image) vs the standard international layout (second image).
 

Jumping Anaconda

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Now I am getting confused. The layout of my A500 matches what you say is the US layout (but obviously with the UK keymap) and that is what every A500 I had seen was like apart from the one I saw at the 1991 World of Amiga.

The one I saw at that show had a case similar to the A500 Plus, but without the Commodore indentation. Instead it had an oblong identation to take an embossed "Commodore Amiga 500" sticker, in the style of the one on the A500 plus.

When did the 8A motherboard go into production? I had a 1990 Screen Gems bundle machine. I would have been really curious to see what that had in it.

Also, has anybody ever come across a 512k A500 Plus?
 

PhilipMcD

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AndyLandy is correct.

There were some vanilla A500 machines which were pretty much just A500+ internally, due to low stock at one point. So a nice little upgrade there, at the time.

So there were A500s that went out with Kickstart 2.0 in them? I know for sure there was a lot of A500+ stock about at the World of Amiga show in 1991. <SNIP>
I wonder if any machines labeled as A500+'s got sent out with 1.3 in them? Or even better, 1.2 :)

What I believe happened, was: (in contrast to the above scenario) you had A500+ machines with the spec of a bog-standard A500 (this was assumed to be down to a transition period).

Interestingly these A500not-so-plus systems still had the the newer OS/Kickstart 2.04 version fitted!

The trick to telling them apart without breaking warranty seal is in the Power/Floppy status LEDs:

A500 (early)
Red Power LED / Green Floppy Drive LED

A500+
Green Power LED / Amber Floppy Drive LED.

This early A500s power light turned off to access the audio filters. Whereas the A500+ only dimmed its LED.
 

Jumping Anaconda

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Was it only the 8A A500s that had the Red light? I had the Green/Amber with the dimming light in my Full ECS machine. I thought the first release Kickstart 1.2 A500s had the red light too, and they switched to Green/Amber dimming when the 1.3 ECS A500s went into production.
 

Firthy2002

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I wonder how many of these A500-not-quite-a-plus machines were made?
 

AndyLandy

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The same was true of that-era A2000s too. r6.x boards sometimes had a mix of OCS and ECS chips.
 

Firthy2002

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But surely mixing the custom chips caused compatibility issues?
 

TheCorfiot

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Not really, apart from WB Screenmode.. No mainstream software really utilised the Super Denise in the A500+ / A500.
1MB ChipRAM AGNES was a different matter however and is the main requirement for ECS gaming.

Super Denise is a nice to have but If you are only interested in playing OCS / ECS Games, it's not worth bothering with

TC :)
 

Zetr0

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as far as I undersand it -

the last true incarnation of the Amiga A500 was the Rev 5 motherboard,

the Amiga A500 rev 6x was the pre-cursor to the A500+


heres a Rev 6 A500 motherboard

a500rev6a-2.jpg

(thanks to amiga.resource.cx)


here is a Rev 8 A500+
a500rev8a-2.jpg

(thanks to amiga.resource.cx)



quite close eh? with just a few minor routing details (and a pin-shifted agnus) these boards are pretty close to identical -

my guess is, that CBM during the transistion were *running the chips out* in the sense of running out of stocks of old chips - hence the A500 Rev 6a had various chips and kick-roms.

This is compounded by the fact of people opening their A500 chassis and finding an A500+ motherboard.



Here - let me show you an eariler A500 design -

here is a Rev 3 A500 (first release)
a500rev3.jpg

(thanks to amiga.resource.cx)

Quite different - now lets look at the last of the REAL A500 motherboad revision

the Rev 5 A500
a500rev5.jpg

(thanks to amiga.resource.cx)



To be honest, I submit upon the court of my peers that the A500 to the A500+ has a logical motherboard progression, hampered by CBM's cost reducing fancey and butchering boards with old stock or last model chips.
 

Jumping Anaconda

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Thank you for the extra info. Did the Rev 6's come with 1 meg of Ram on the motherboard? It strikes me that if they were running out stock on the Rev 6's then they would not have the RAM in the format used on the A500+'s in denominations to make 512k in the required slots?

Is the Ram those banks of chips at the bottom nearest the trapdoor connector?
 

quarkx

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Doesn't the A500+ have the battery on it also, the pictures don't show a battery (or I can't see one anyway)?
All my A500's have the rev.5 Mobo :( I don't think the "+" was even sold here in Canada
 

Zetr0

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Well this is interesting,


If every one has a look at this - A500+ Rev 8A that I posted earlier

here is a Rev 8 A500+
a500rev8a-2.jpg

(thanks to amiga.resource.cx)


You will note that only 4x HYB514256 (4bit * 256) is installed - in this configuration that is ONLY 512KB -

This revision A500+ is most certainly a transition board of sorts... interestingly its fitted with a 2MB Agnus as well (8375 / 3190544)



However now check out this 8A revision

a500rev8a.jpg

(thanks to amiga.resource.cx)


Notice how the chip ram is fully populated with 8x (4bit *256) = 1MB
 

Jumping Anaconda

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Does the 512k 8A have an NTSC chipset (I can't see from the image)? Maybe it was for a US A500 produced after the A500+ was released in other parts of the world?
 

quarkx

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Ah!, Now I see the battery (or lack of one) on that first motherboard.
Also notice the extra IC that I circled, I am not sure what it is, but it was left out on the other picture.
 

rkauer

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To quench the discussion:

In fact, rev6 A500 was not exactly a transition board, but in fact a cost-reducing one! It have 512kb on board with the first FAT Agnus (1Mb chip RAM support, which is not ECS in my pow) with lesser number of RAM chips.

Interestingly this board have space to solder the full 1Mb directly on it as an rev6 OCS A500 with full 1Mb from factory never saw the light of day. True C= style.

The 8A board revision is a very different beast!

It is the A500+ board and after big C selling the lot of remaining OCS A500 they start to ship the regular 500 with the 500+ boards, just sacking out the 4 extra chips who comprise the full blown 1Mb. Those few happy costumer with had the luck of buying one of those infact have a half-megabyte A500+.

More to come on this subject.

---------- Post added at 16:03 ---------- Previous post was at 16:00 ----------

Ah!, Now I see the battery (or lack of one) on that first motherboard.
Also notice the extra IC that I circled, I am not sure what it is, but it was left out on the other picture.

That "extra" IC is the one who gives the extra address lines to hook the last 512kb directly on board to A500+ models.
 

TheCorfiot

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I fully agree with Rogerio :nod:

The rev 6A is the last true A500 board, like the A2000's rev 6 series, These Rev's were a redesign to take the different larger RAM chips, reducing chip count & costs.. The Rev 6A is indeed an OCS board as it can only handle Max 1MB chipRAM without addon boards such as the MegaChip.

Of course Rev 6 A2000 boards also contained other fixes too.

TC :)

Dig the pr0n though Zeets :LOL:
 
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