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AuthorTopic: For A500+ : Mini Mega Chip 2.1 OR MegAchp 2000/500  (Read 648 times)

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Offline KLund1

For A500+ : Mini Mega Chip 2.1 OR MegAchp 2000/500
« on: March 28, 2022, 06:38:59 AM »
Hello,
  I have a A500+ (plus) this an Agnus(fat Lady) 8375R0 installed.
I also have a DCE Mini Mega rev 2.1 just like pictured below.
https://www.vesalia.de/e_megi.htm

and a

DKC(?) MegAchip 2000/500 with an 8372B installed
https://bigbookofamigahardware.com/bboah/product.aspx?id=1941

Which would be a better upgrade for the A500+ ?
I'm still a little new the Amiga and I'm learning as I run into things.
 

Offline zipper

Re: For A500+ : Mini Mega Chip 2.1 OR MegAchp 2000/500
« Reply #1 on: March 28, 2022, 11:25:22 AM »
Neither. You just need 1 MB memory expansion suitable for A500+

Offline Matt_H

Re: For A500+ : Mini Mega Chip 2.1 OR MegAchp 2000/500
« Reply #2 on: March 28, 2022, 04:40:34 PM »
Expanding on zipper's comment, you need something like this that slots into the trapdoor. There are lots of boards like this out there that can be bought from your preferred vendor or eBay.

The MegAChip and such are for the regular A500 (non-plus), which is only capable of addressing 1MB of Chip RAM (512K onboard and 512K in the trapdoor). The MegAChip makes those machines capable of addressing 2MB of Chip RAM: new Agnus and 1MB RAM on the MegAChip + 512K on the motherboard + 512K in the trapdoor.

Offline KLund1

Re: For A500+ : Mini Mega Chip 2.1 OR MegAchp 2000/500
« Reply #3 on: March 28, 2022, 08:08:35 PM »
Many thanks!
Understood.
Neither needed for a standard A500+
Looking at ACA500plus. This seem to be the  "Swiss army knife" type solution for p[resent and also further upgrade. I do not mind it being outside the case. 
Again thanks
 

Offline Matt_H

Re: For A500+ : Mini Mega Chip 2.1 OR MegAchp 2000/500
« Reply #4 on: March 28, 2022, 09:02:18 PM »
ACA500plus is a good choice, but you should still get a trapdoor RAM expansion. If you're new to the Amiga, note that it has two different kinds of memory: Chip and Fast. The ACA500plus will give you Fast RAM, but only the trapdoor bus can give you Chip RAM. A full 2MB of Chip RAM will make life much, much easier for whatever you're trying to run.
 

Offline KLund1

Re: For A500+ : Mini Mega Chip 2.1 OR MegAchp 2000/500
« Reply #5 on: March 28, 2022, 09:20:25 PM »
Wow, more info for my Amiga nube brain. Thanks.
Any suggestions for a reasonable 2mb trap door ram upgrade?
Or do i need just 1mb? my PCB has 8  256Kb chips on it. is that 1Mb on board?
Is there a upper limit for the amount of 'Chip Ram' a 500+ can access?
I will be running 1.3, 2.04, & 3.1 kickstart's in a switchable PCB I have.
 

Offline Matt_H

Re: For A500+ : Mini Mega Chip 2.1 OR MegAchp 2000/500
« Reply #6 on: March 29, 2022, 12:10:06 AM »
2MB is the limit for Chip RAM. Every A500+ has 1MB onboard and can take an additional 1MB via the trapdoor. Like zipper mentioned, you need a 1MB trapdoor expansion suitable for the A500+. There are lots of these on the market, vintage and new, like the one I linked (Individual Computers, maker of the ACA500plus, also has one). Just make sure it's an A500+/1MB expansion and not an A500/512K expansion. If it has a clock/battery on it it's for the plain A500 - the A500+ plus has a clock on the motherboard and so its trapdoor expansions don't include one.

Offline KLund1

Re: For A500+ : Mini Mega Chip 2.1 OR MegAchp 2000/500
« Reply #7 on: March 29, 2022, 12:30:25 AM »
Understood.
Again thanks for all the help.