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Author Topic: 2MB Chip RAM directly on A500 rev. 6 motherboard?  (Read 14487 times)

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Offline czarekTopic starter

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2MB Chip RAM directly on A500 rev. 6 motherboard?
« on: October 17, 2008, 12:56:31 PM »
Hi, I know it is possible as I saw few people did it. My question is - how?
I have already soldered whole megabyte onto motherboard and re-soldered jumpers so it's visible as 1MB Chip RAM. The possible problem may be that it's pre A500+ motherboard. It had space for 1MB ram and 8372 Agnus, but doesn't have space for RTC circuit and when I put 8375 Agnus it just gives me black screen. Was no problem with replacing Denise to full ECS though.
So all of you A500 experts - please share your secrets :-)
Thanks in advance!
 

Offline countzero

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #1 on: October 17, 2008, 12:59:05 PM »
it is not possible without some extra logic. And 2mb agnus has a different pinout I believe.
I believe in mt. Fuji
 

Offline czarekTopic starter

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #2 on: October 17, 2008, 04:21:57 PM »
Ok I just found out that my Agnus 8372A is full ECS Agnus that supports 1MB Chip RAM, only ones that support 2MB are 8372AB and 8375. I have two 8375 Agnus chips, both tested working in real A500+ but when I put them in my motherboard it just doesn't start up. Very strange. I'm wondering if it has anything to do with jumpers? When soldering my actual memory I had to cut JP4, and switch JP2 and JP7A. I just spotted there are 3 jumpers labeled JP5 just next to Agnus. I can't find any information about them - does anybody know what is this one for?
 

Offline Metalguy66

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #3 on: October 17, 2008, 11:23:56 PM »
There are no jumpers on a Rev 6a motherboard that pertain to 2megs chip ram.

The problem you are having with the 2meg AGNUS is that quite a few pins on the 8375/8372B (2meg AGNUS) are in different locations than they were in on the 8370/8372A (512k/1meg AGNUS).

You would have to seriously hack the hell out of your motherboard (I mean cut MANY traces and rewire the circuits, and also add quite a bit of additional circuitry that isnt even there) to put 2 megs of chipram on the motherboard.

What you can do is find a DKB Megachip which is a small board that plugs into the agnus socket and has an extra meg of ram already on it, along with a 2meg AGNUS and the additional circuitry to make it work.

http://cgi.ebay.com/DKB-MegAChip-2MB-CHIP-RAM-for-Amiga-500-2000-Toaster_W0QQitemZ320309731919QQcmdZViewItem?hash=item320309731919&_trkparms=72%3A1209%7C39%3A1%7C66%3A2%7C65%3A12%7C240%3A1318&_trksid=p3286.c0.m14

Your other option, of course, is to get an A500+ (rev 8a) motherboard.
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Offline redrumloa

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #4 on: October 17, 2008, 11:40:04 PM »
@Metalguy66

That is a seriously good price for a MegAChip, it will be snapped up soon. I just picked up 3+ of these, but I doubt I'll list them that low :-o
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Offline countzero

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #5 on: October 18, 2008, 12:09:00 AM »
@Red, you're kidding right ? (just to make sure  :crazy:  :lol: )
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Offline redrumloa

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #6 on: October 18, 2008, 12:11:31 AM »
Quote

countzero wrote:
@Red, you're kidding right ? (just to make sure  :crazy:  :lol: )


No, if I was to put one up straight auction I'd get north of $150, possible even north $200. While not rare, they are uncommon enough to command those prices.
Someone has to state the obvious and that someone is me!
 

Offline countzero

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #7 on: October 18, 2008, 12:15:47 AM »
How come I sold 2 (one in box) for 50$-60$ each last year ? (all scavenged from dead japanese a2000 boxes) and that's ebay prices. You will never get 150$ for that and even that buy it now price is a joke for me.
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Offline redrumloa

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #8 on: October 18, 2008, 12:20:24 AM »
Quote

countzero wrote:
How come I sold 2 (one in box) for 50$-60$ each last year ? (all scavenged from dead japanese a2000 boxes) and that's ebay prices. You will never get 150$ for that and even that buy it now price is a joke for me.


 :shrug:

Are you sure you are not confusing 2MB Agnes with Megachip?
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Offline alexh

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #9 on: October 18, 2008, 12:30:25 AM »
You'd never sell any at $150-200!

This vendor has access to the back stock and has sold several of these for $90 in the last year or two.

Plus who in their right mind would pay $200 for a MegaChip when you can get an A500+ for $3-10
 

Offline redrumloa

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #10 on: October 18, 2008, 12:34:02 AM »
Quote

alexh wrote:
You'd never sell any at $150-200 because this vendor has sold erm lots of these for $90 in the last year or two (probably has more).
 


What dealer? All I am going on is the last couple auctions I have seen.

Quote
lus who in their right mind would pay $200 for a MegaChip when you can get an A500+ for $3


Err, right :lol:

-Edit-
I just sold a reglular A500 with imperfect case for 10x more than $3 and it sold like lighting at that price.
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Offline alexh

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #11 on: October 18, 2008, 12:36:21 AM »
Same guy sold one recently for $99

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320282336765

I think I bought mine from this same guy 3-4 years ago for $59 which goes to show how many he's got / had.

Quote

redrumloa wrote:
Quote

alexh wrote:who in their right mind would pay $200 for a MegaChip when you can get an A500+ for $3


Err, right :lol:

Right.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=300266237314

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=300265527532

Wedge shaped Amiga's are practically worthless.

Quote

redrumloa wrote:
I just sold a reglular A500 with imperfect case for 10x more than $3 and it sold like lighting at that price.

Maybe the redrumloa in the auction makes it worth more. A sort of provenance?
 

Offline redrumloa

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #12 on: October 18, 2008, 12:43:45 AM »
Quote

alexh wrote:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320282336765

I bought mine from this guy 3 years ago for $59


That link shows a sold one for $99, which you just said was a joke. but anyhow, this conversation is getting boring. Whatever I list it for, if it doesn't sell, I lower the price. That's capitalism. Since you have so kindly pointed out them selling for less than I've seen, I'll take that into advisement.

Quote
Err, right  

--------------------------------------------------------------------------------
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=300266237314


Not a full A500+. I get your point, but I disagree. That is like saying, just get an A2000 or even just get a PC. If someone wants a certain piece of hardware, they want that hardware.
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Offline alexh

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #13 on: October 18, 2008, 12:49:06 AM »
I am just trying to urge people who might be reading this and considering paying those prices to stop and think again.

A500, especially in UK, is worthless. Millions were made and there is a large supply of them even the 2Mbyte capable A500+

Hold out for a bargain. I guarantee you wont have to wait long.

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

Offline Metalguy66

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Re: 2MB Chip RAM directly on A500 rev. 6 motherboard?
« Reply #14 on: October 18, 2008, 12:50:29 AM »
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.

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