AdRAM 540 with A500+??

[K7HTH]

Is this possible? Does it work? I tried it with no success and wondered if it was just me or is this the rule with the A500+?

[Cyberus]

I have no experience with that expansion, but I see absolutely NO reason why it shouldn't work.

[K7HTH]

Thanks for the encouragement Cyberus. I am eagar to know of anyone else's experience with this.

[doctorq]

I haven't tried to use this ram expansion in an Amiga 500+, but I had one that was working perfectly in my Amiga 500 with Kickstart1.3. IIRC there is a block on the ram card that is used for giving 1 MB chip ram, and since the Amiga 500+ already has this, this might be the problem. Look in your manual, I think the drawings says it all.

How much ram do you have on it? If it's fully populated I would try to stripping it down to only containing 512 KB, to see if the computer starts up. If it does, at least you know it's working.

Btw. I fried a 1.5 MB ram expansion for my A500 today :-(

[doctorq]

Maybe try to place your ram chips like on  this board. As the page says, the AdRAM should be able to run in your Amiga 500+.

[K7HTH]

Thanks for the tips! My A500+ has the standard 1MB Chip RAM. The instructions say to only jump the daughter board to the JP2 center pin to add 512Kb to Chip RAM if a Fatter Agnus is installed. I plugged the fully populated board into the expansion slot along with the Gary DB and the ram was not recognized. I connected the jumper to the JP2 from the DB and it did not boot. I then cut JP2 contacts 2-3 because the jumper must connect to the center (2) contact. Boot but not recognized. This rev 8A board is so sweet and clean and I am the only one to have attempted to mod it in any way. If I reduce the chips on the AdRAM 540 from 4MB to 512Kb then I defeat the purpose of the RAM increase and therefore should just get the 1MB chip RAM expansion for the A500+ but I want to have more, hence the AdRAM 540. The photo you show has chips removed to accommodate the AdRAM 560 2MB expansion to the AdRAM 540, I don't think that applies to my situation here. Thanks again!

[doctorq]

I was suggesting you to strip the board down to 512 K in order to check the board if it's working or not. If it works with 512 K you can add memory in sizes of 512 K, and when RAM isn't recognized anymore, you know where the problem is.

[K7HTH]

Hmmmmm, ok that makes sense. But this AdRAM 540 works like a champ with all 4MB on an A500 plain. I read somewhere on the net in a group discussion about this board that is does not work in the A500+. But I am not satisfied with such an unsubstantiated statement, hence my posting here at the home of Amiga hardware authority. I will consider the chip removal but I hate to do it.  

[Argus]

I believe the AdRam540 won't work at all on the A500+ because the memory addressing on the board is such that the first 512K on the board will only map to the second 512K of the first 1MB of chip ram (with Fat Agnus 8372A/B) or default to the slow fast mem 512K of unmodified Rev.5, 6A motherboards w/ 8370 Agnus.  Since the A500+ has this memory on board (addressed by Agnus 8375) the first 512K of physical memory on the AdRAM can't be recognized.  I don't know about the physical addressing of additional memory on the AdRam board but it is probably in the 4MB+/- limit that standard Gary can address via the trapdoor slot.  Though it is pin identical, the A500+ trapdoor slot differs from the A500 slot in that it was built to accept a 1MB chip ram card that Fat Agnus 8375 would address at a location unavailable to the slot of the A500.  For the same reasons A500 users need a MegaChip or like board in the Agnus PLCC slot itself to add an extra 1MB chip mem afaik.

[K7HTH]

Good point Argus. I suppose I need to remove the  bank 4 chips that support the 512K to Chip RAM. Looks like some more testing to be done, something that makes this hobby so fun. The link above describing the AdRAM board says A500(+) compatible so I must work with this to make it happen.

[K7HTH]

Well, when I remove chips, or add the DB jumper, or cut JP2 to reduce the 1MB Chip to 512Kb to allow the AdRAM 540 to add the RAM all the symptoms are the same, either a locked gray screen, or a guru meditation equivilant with 2.04 ROM. I think the problem lies in the Fatter Agnus 8375 that makes the AdRAM 540 uncompatible. Why does the A500+ need an 8375? Shouldn't an 8372A accommodate the same 1MB Chip RAM? Still working this out. Next experiment is to make the A500+ an A500 plain.  

[K7HTH]

Well, looks like the A500+ will not accept the 8370 or 8372A Fatter Agnus. The 8370 won't boot, the 8372A emits a solid green screen. So the task to make an A500+ an A500 plain is not possible because removing the chip ram and the Agnus does not effectively change the A500+ architecture. Back to the AdRAM board.

What I get with the AdRAM installed is the 2.0 ROMS WB prompt screen, so the system boots. The problems arise when I try to load WB. The system hangs before the WB loads. How the AdRAM causes this is unknown to me. Anyone have a guess why?

[K7HTH]

I tried booting with WB 1.3 and because the only Wb 1.3 disk I have has a read error, I could not access WB, but at least the read/write error stopped after Amiga DOS loaded so that is where my 1.3 kickstart disk left me. Well, from there I was able to enter commands and entered AVAIL and got the message that I have 1MB of chip ram with my AdRAM installed! I cut off 512Kb by opening JP2 2-3 to isolate connection to pin 2 from the DB in accordance with the instructions for an 8372A. Now if I could only get WB to load and see if the AdRAM will autoload as fast ram. Anyone willing to sell me a copy of WB 1.3?