2MB Chip RAM directly on A500 rev. 6 motherboard?

[Metalguy66]

A500+ is pretty damn rare in the states.

If I didnt already have 2 spare 8a boards, I'd pay the overseas shipping and buy that one.

[redrumloa]

P.S. I would never recommend an A2000. They are the worst Amiga. They have no redeeming features.

Are you Doomy's alter ego?  :lol:

I am just trying to urge people who might be reading this and considering paying those prices to stop and think again.

Why don't you open am eBay store and sell this hardware for what you think is fair? Like tested A500 motherboards for $3.

[alexh]

Oh come on! They dont :-)

No AGA, no scandoubler, no Zorro III, no IDE. Unless you already have one, or can get one for free, you steer clear.

I imagine that MegAchips mainly end up in CDTVs? It's what I bought mine for.

They are the only Amiga where there is no real upgrade alternative. (CD32 just isn't the same)

[redrumloa]

alexh wrote:
I imagine that MegAchips mainly end up in CDTVs? It's what I bought mine for.

I think they mainly end up in A500s, but that is a guess.

[alexh]

redrumloa wrote:
Why don't you open am eBay store and sell this hardware for what you think is fair?

Totaly off on a tangent, I dont understand the economics of eBay for most second hand vendors. I cant be arsed to sell any of my old stuff via ebay. I can make more money doing something else in the time it takes to compose the advert and go to the PO.

[redrumloa]

I can make more money doing something else in the time it takes to compose the advert and go to the PO.

That is my point :-)

[tabuhuso]

Note:
2mb DKB megachip no working on ecs PAL amigas...

[amigaksi]

I have an Amiga 500 with 2MB chip ram; don't recall which revision of motherboard it is but there's no DKB or any other expansion installed.  

[alexh]

tabuhuso wrote:
2mb DKB megachip no working on ecs PAL amigas...

Yes they do!! But you need a PAL version. (The ones being sold on eBay are mainly NTSC ones)

If you have an NTSC version you need to make a note of the EXACT model of 8375 Agnus in them and replace it with it's corresponding PAL version. They must be the same because the pinout changes between variants.

i.e. If your NTSC DKB MegAChip has a

8375 318069-11 replace it with 8375 318069-10
8375 390544-02 replace it with 8375 390544-01
8375 318069-19 replace it with 8375 318069-18

You can buy PAL 8375 Agnus chips from Amiga Center France for about €45 each (which is not cheap after you've already paid $89 for the MegAChip!) or you can scavenge them from broken A600's (if you have a hot-air gun) & A500+'s (which tend to break due to their battery leaking)

amigaksi wrote:
I have an Amiga 500 with 2MB chip ram; don't recall which revision of motherboard it is but there's no DKB or any other expansion installed.  

It's an A500+ (rev 8a)

[Metalguy66]

Wow, thanks for those part numbers, AlexH. As I understand it, the left column is NTSC and the right column is PAL?

Do you by any chance have documentation on exactly what pin changes are involved between serial numbers?

[alexh]

Yes, NTSC on the left PAL on the right.

I have *some* documentation on the pin changes between the different Agnus main variants (8370, 8372, 8372AB, 8375) but very little on the differences between the minor variants.

Not for trying, I've run several threads to try and nail down Agnus details. Of all the Amiga chips it is the one that changed the most and known the least.

Amiga.org thread

EAB Thread

EAB thread about pinouts

Newsgroup thread

[Metalguy66]

Well, soem differences can be seen in the schematics.. eg. A600 vs A500+ vs A3000...

Do we know which part numbers went to which machine?


heres another one.. from austrailia, I assume it's PAL.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=310092493455&ih=021&category=4598&ssPageName=WDVW&rd=1#ebayphotohosting

8372B 318069-03

[alexh]

8372B 318069-03 is on record as having been seen in an NTSC A3000D. But I do not think it is accurate to call it NTSC. I *think* all 8372 Agnii are dual standard supporting both PAL & NTSC (at least some are). So this board probably works with both although you might need to mod your Amiga motherboard depending on its PCB version to make it drive the NTSC/PAL select pin correctly.

There is no direct mapping between model numbers and machines.

Rule of thumb:

A500+ = 8375 390544-01/2
A600  = 8375 318069-10/11
A3000 = 8372AB / 8372B 318069-03

But it is just a rule of thumb and it doesn't always hold true. Later revisions of A500+ motherboards sometimes have 318069-10/11, early A600 motherboards have 390544-01/2 and later revisions of A3000 have 8375 318069-18/19

[czarek]

I've got couple of A500 plus, all dead due to battery leakage :-( but their Agnuses (8375) are working in rev 8a A500...

[Metalguy66]

Ok. According to the Commodore service manual schematics,

the A500+ and A600 agnus chips should be interchangeable.

The A3000 agnus has about 20 signals that are "shifted" by one pin number.

The service manuals list the A500+ and A600 AGNUS as part numbers: 390544-01(pal) and 390544-02(ntsc). The A3000 AGNUS is listed as 318069-03.

[alexh]

A600 use AGNUS part numbers 390544 only on v1.0 motherboard. They use 318069-10(pal) and 318069-11(ntsc) on motherboards v1.3, 1.5 and 2D. No idea what the pinout differences are (if any).

I found it difficult to read the pin numbers on the A600 schematics I could find online they are too blurry. The ones I found had no validation data either (i.e. you've no idea where they came from, which motherboard version they correspond to or which agnus chip is described on them)