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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: save2600 on August 29, 2010, 11:24:44 PM

Title: Quick 1MB Agnus and OCS Denise question on A2000
Post by: save2600 on August 29, 2010, 11:24:44 PM: Okay - pretty much built a nice looking and complete A2000 from leftovers and parts from my own stock as well as Fester here (thanks man!), but something's got me momentarily stumped... 8372A Agnus, jumper setting to enable clock and extra 512KB as Chip, but... no matter what, I only have 512k Chip and 512k Fast. Actually, 8.5mb Fast with this other card installed. I do NOT have an ECS Denise in this machine. I could have sworn I've seen 1MB Chip before with the regular 8362R8 Denise and 8372A Agnus - but am I mistaken?

Must you have an ECS Denise in order to get more than 512k Chip?

BTW: Fester... that 6.x mobo you gave me does not work. Acid creeped up much worse than I thought. Got up 1/3rd of the way into the 68000. Since I had another mobo, I'm simply working off that now instead of tracking down traces on yours. Will simply keep that as my "new" spare. lol Kickstart 3.1 chip off that works great though :)
Title: Re: Quick 1MB Agnus and OCS Denise question on A2000
Post by: Matt_H on August 30, 2010, 12:27:26 AM: That Agnus should definitely give you 1MB of Chip. What revision motherboard is it?
Title: Re: Quick 1MB Agnus and OCS Denise question on A2000
Post by: save2600 on August 30, 2010, 12:35:39 AM: Yeah, that's what I thought. It's a rev. 6.2 mobo.

Alrighty... figured it out. J102, which was just a couple of solder pads, had solder splashed between 'em. Desoldered the pads, moved J101 to the right AND opened J500 - voila! There's my full 1MB Chip RAM :drink:

Totally goes against what I've read in English online (BBOAH), but after some German translating on other sites - got the desired results. Yay!
Title: Re: Quick 1MB Agnus and OCS Denise question on A2000
Post by: desantii on August 30, 2010, 02:22:08 AM: You beat me to it, its definitely a combination of J101 and J500.

J102 just chages teh deafualt from NTSC to PAL

ECS Denise will give you higher resolutions
Title: Re: Quick 1MB Agnus and OCS Denise question on A2000
Post by: save2600 on August 30, 2010, 02:28:33 AM: I tried the J100/J500 combo - didn't work until I desoldered what's supposed to only be the PAL/NTSC switch at J102. Strange as shit, but whatever. It's done! :drink:
Title: Re: Quick 1MB Agnus and OCS Denise question on A2000
Post by: Zac67 on August 30, 2010, 11:32:45 AM: Could only imagine the J102 jumper being a problem when the Agnus is no ECS afterall... Better check that all Chipram is functional.

You can also set up an OCS Agnus with 1 MB chip, but it'll crash the machine when the first 512 KB run out. (The missing bit in Agnus' address registers will make the address wrap around to the lower 512 KB and trash some other data there.)
Title: Re: Quick 1MB Agnus and OCS Denise question on A2000
Post by: Amiga_Nut on August 30, 2010, 01:00:29 PM: If you need an ECS Denise let me know, I have two available and only need one for when/if I ever find another A2000 motherboard.
Title: Re: Quick 1MB Agnus and OCS Denise question on A2000
Post by: joekster on August 30, 2010, 02:42:53 PM: I too have an acid dammaged A2000 rev 4.? motherboard. The 68000 socket is dammaged so that the machine doesn't boot. BUT, the fast slot (accelerator) still works. I was able to use the machine just fine with NO 68000 and an a2620 installed! Depending on the damage, this may work for you...
Title: Re: Quick 1MB Agnus and OCS Denise question on A2000
Post by: Fester on August 30, 2010, 05:12:40 PM: Hi save2600,

It was nice to meet you finally. Thanks for coming over. Glad you can use the equipment.
Title: Re: Quick 1MB Agnus and OCS Denise question on A2000
Post by: save2600 on August 31, 2010, 01:21:51 AM: Yes, you too Fester and thanks again for the Amiga goodies :)