Fatter Agnus

[ceaser]

oops is it Agnes?
Hi,

I have an Amiga 500 plus.  I just grabbed it off ebay.  I popped the bottom off and it has the socket for the RAM upgrade with no chip on it.  I kind of thought the "plus" meant it had the chip in it.  This is used off ebay and not even tested yet.  It was purchased from and probably made for sale in the UK.  I used to have an Amiga 500 that was made/sold in the USA back in 1990 when it was new stuff.  And I'd upgraded it with an easy to find chip at the local Amiga store (and of course I don't remember exactly what it was called on the box).  My friend Dan told me (back in 90') I was upgrading my Agnus chip to a fatter Agnus chip (512 KB to 1 MB of RAM).  What is the part # or best way to identify when searching stores online & ebay for the 512 KB upgrade?  Also, does the "plus" have 1 mb already without having to purchase a RAM upgrade?  Or did someone indeed remove the additional 512 KB chip out of the machine?  Most important to me is that it can play games that require 1 MB because a lot of the good Amiga games do require that.

If I was too lengthy in my description just note I'm talking about upgrading the RAM you put in the pop-off area on the bottom of the A500/A500+(in my case a +) that does not involve opening the whole unit.*:hammer:

also is that ami-pc toolkit worth buying?  i was going to get a null modem cable but i'm thinking it'd be awfully hard to find the Amiga side of the software on DD floppies.

[Jiffy]

The A500+ normally has a 2 MB Agnus inside, with 1 MB of ram on the motherboard, all of it chipram. To get 2 MB of chipram, you would need a trapdoor memory card with 1 MB. 2MB is the maximum amount of chipram you can get on an A500+.

The BBOAH can give you some extra info on the (relatively minor) differences between a normal A500 and an A500+.

[dougal]

The difference between the A500 & the A500+ are as said above , the A500+ has the Fatter Agnus supporting 2Mb Chip Ram which no other Amiga , not even the A4000 can support more than 2Mb Chip .

Also the A500+ has the ECS chipset which has a newer Denise chip supporting more screen modes than the A500 .

Also a RTC (Battery backup Realtime Clock) is standard in the A500+ as is Kickstart 2.04.

You might want to check out the battery inside it . **ALL** my A500+ machines suffered the notorious leaking RTC Battery and it WILL cause damage to the motherboard .

Even if the battery looks ok , please remove it right away . Its pretty easy to remove .
Some say you can desolder it , which is prob the best option , but i used plyers and gentley wedged it off the board .

[jj]

From the subject I thought this was news that burger king had released an even bigger angus burger.   Gutted now

[dougal]

From the subject I thought this was news that burger king had released an even bigger angus burger.   Gutted now

[ceaser]

thanks!  yes i'm going to open it up and put my spare cr2032 battery in there hopefully.  i hope that's the kind it takes because that's what i have :/  i grabbed the 1 mb of trapdoor RAM that i believe according to the BBOAH is compatible with a PAL 500+ which is what i got.  23-pin to 9-pin monitor cable along with probably a standard 9-pin PAL to NTSC converter will be all i need for display.  i don't think you could find a NTSC + and that's what i wanted so i grabbed it.:afro:

it needs 3x6v GP56K batteries and they're really jammed in there and in a blue binding of some sort.

also just to elaborate although i pretty much got my questions answered this A500 plus unit has a fatter agnus identified as such:
CSG
390544-01
8375
4391 20

[Matt_H]

You can use a regular CR2032 battery as a replacement if you add a diode to block the recharging circuit. Full info on this hack is on Aminet and elsewhere, and DJBase here at Amiga.org has made some PCBs with CR2032s and diodes that can be dropped in directly. The battery isn't critical to operation, though.

Make sure any trapdoor RAM you buy has 1MB onboard. Most of the trapdoor RAM cards out there are designed for the 500-non-plus and contain 512K, but are sometimes confusingly referred to as 1MB expansions since they bring the total RAM of a regular 500 to 1MB (500+ has 1MB out of the box). Vesalia has full 1MB cards.

[ceaser]

i was posting all that info because i'd just opened up an amiga 500 for the 1st time.  wanted to see mostly what battery it took and if it could be replaced and what the exact model #'s were on all the chips.  also was trying to replace some keys in a professional way but looks like Amiga 500 has the weirdest keys ever and they don't really pop in and out like keys on other keyboards.  that battery hack sounds interesting.  

that old one was stuck in there really well though.  it didn't appear to be corroded yet at all so i don't think replacement is critical, but im doing it anyway.  for the keyboard i saw at least 1 listing on ebay for just the keyboard part which is the easiest thing to replace in the amiga 500.  if i can't get it cheap then it's not going to matter much since i'm not using it for word processing.

after finding a battery: It's strange it's a rechargable rather than lithium.  Yes the crap that comes out of especially Ni-CD is really bad.  Also for the gentleman who made this suggestion I have a question; it has 2 metal things on either side that appear  like the 2 contacts that pinch the battery in place, but the battery didn't seem to want to come out of those and it didn't seem corroded so i didn't take it out yet.  but have ordered a definite, claimed to be brand new replacement for that horribly strange battery in there (horrible as in not at your local radio shack but id already seen a listing for it on ebay and it was like 5 bux shipped so i couldn't turn it down).

It looks like in the picture they show in the listing that what I thought were contacts are actually part of the battery.  Do you carefully but forcefully yank the old one out?  Then it comes out with a prong on either side sort of.  And no I definitely don't think solder is needed here at all like you say.