A500 trapdoor memory: free design

[hooverphonique]

Originally Posted by toadnode

Looks like it says Kic TBE841684C 00434

With 18 years of experience, you should be able to google a datasheet yourself (hint: that code doesn't give any hits).

[toadnode]

Originally Posted by hooverphonique

With 18 years of experience, you should be able to google a datasheet yourself (hint: that code doesn't give any hits).

I wasn't blowing my own trumpet, just saying it's properly "assembled". I'm a tech, not an engineer. Google didn't return any results for these numbers so I thought I'd turn to the forum for a little help. Cheers.

[toadnode]

...and the numbers I've quoted could be wrong. Even with a high res camera it's difficult to make out after cleaning the sticker off the chip.

Anyway, should I just look for another chip or is there another reason why this may not be working for me?

[PeteAU]

Originally Posted by toadnode

...and the numbers I've quoted could be wrong. Even with a high res camera it's difficult to make out after cleaning the sticker off the chip.

Anyway, should I just look for another chip or is there another reason why this may not be working for me?

How you described the jumpers sounds all good and correct. And the "8M EDO" sounds right too (it was probably 4 chips on a SIMM stick). It's got to be something simple, one out of 42 pins not well joined? Is the RAS jumper above the DRAM chip joined to something?

You could run keirf's Amiga Test Kit and do a direct memory scan (bypass kickstart) and see what it throws up.

[toadnode]

Thanks for the feedback Pete. I'll try re-solder the chip. The RAS jumper is just default RASU1-RAS1. I did try the direct memory scan last week and ran into a Guru after a certain point but it was pretty late and called it a night at that point. I might look a bit further into that.

[Mathesar]

Originally Posted by toadnode

Thanks for the feedback Pete. I'll try re-solder the chip. The RAS jumper is just default RASU1-RAS1. I did try the direct memory scan last week and ran into a Guru after a certain point but it was pretty late and called it a night at that point. I might look a bit further into that.

Also, If I remember correctly: The gary adapter is responsible for making the Amiga "see" the extra memory. The fault could thus also lie there if you don't see any extra memory at all.

[Mathesar]

Originally Posted by toadnode

Hi guys, great thread here! Nice to see Amiga users doing what they do best...helping each other out :-) Hopefully someone can help me now...
I bought this kit (Bruktmoped edition board) off ebay recently. I've put it together but I'm not seeing either Chip or Slow RAM. The RTC is working fine however.
My A500 is rev 5 and the EXRAM line on motherboard is cut, JP2 changed and 8372A Agnus in place.
I consider myself fairly confident with electronics assembly having worked in the industry 18 years. I've checked for shorts and found none but I am curious about the RAM supplied, it had a sticker on top saying EDO 8M which I've now cleaned off to get a better look at the numbers. Looks like it says Kic TBE841684C 00434
Any suggestions appreciated! Thanks!

Why did you cut the exram line? On my rev5 I have it in place and jumpered to ground on the ram expansion. Otherwise it won't work.

[cmorley]

@toadnode: What kickstart do you have on the rev 5? Kick 1.2 will crash with a yellow (iirc) screen with Gary adapter RAM I think. Kick 1.3 is fine.

[majinga]

Originally Posted by cmorley

@toadnode: What kickstart do you have on the rev 5? Kick 1.2 will crash with a yellow (iirc) screen with Gary adapter RAM I think. Kick 1.3 is fine.

Works well with KS 1.2, just set the GA jumper to 1 MB slow

[toadnode]

Originally Posted by Mathesar

Also, If I remember correctly: The gary adapter is responsible for making the Amiga "see" the extra memory. The fault could thus also lie there if you don't see any extra memory at all.

OK, my kit didn't come with any Gary adaptor ;-(

[toadnode]

Originally Posted by Mathesar

Why did you cut the exram line? On my rev5 I have it in place and jumpered to ground on the ram expansion. Otherwise it won't work.

I followed various tutorials which said in order to make the upgraded Agnus (8372A) address 1MB chip ram, the rev5 needs EXRAM line to be cut and J2 switched(cut/soldered to other pad). Is this not the case?

[toadnode]

Originally Posted by cmorley

@toadnode: What kickstart do you have on the rev 5? Kick 1.2 will crash with a yellow (iirc) screen with Gary adapter RAM I think. Kick 1.3 is fine.

I have KS1.3 but also an HC508 with KS3.1.4 flashed.

[cmorley]

Originally Posted by toadnode

I have KS1.3 but also an HC508 with KS3.1.4 flashed.

HC508 manual says it is not compatible with Gary adapter RAM.
http://irixlabs.com/files/HC508%20qu...guide%20EN.pdf

[Mathesar]

Originally Posted by toadnode

I followed various tutorials which said in order to make the upgraded Agnus (8372A) address 1MB chip ram, the rev5 needs EXRAM line to be cut and J2 switched(cut/soldered to other pad). Is this not the case?

This is the case only when you want a standard 0.5MB trapdoor ram board configured as fast ram.
Not when you want to use this gary adapter to make 1MB chip (total) + 1.5MB slow.

To use the gary adapter you need to restore the EXRAM line (it should be grounded by the trapdoor board). The center pad of JP2 should not be connected to either outer pad. Instead, the center pad of JP2 should be connected to the Gary adapter via a wire.

The wire is needed because the gary adapter needs to control which 0.5MB bank on the trapdoor board is chip or slow ram. EXRAM is needed because otherwise the address decoding does not work correctly.

[toadnode]

Sigh... Ok, I stuffed that one up!

Reading the first post I got the impression the Gary adaptor was for 1.5mb chip only. And the tutorial for the 8372a was all I needed to make trapdoor RAM chip. Oh well, need to find an adaptor now I guess.

Thanks for clearing that up guys.

[PeteAU]

Originally Posted by toadnode

Sigh... Ok, I stuffed that one up!

Reading the first post I got the impression the Gary adaptor was for 1.5mb chip only. And the tutorial for the 8372a was all I needed to make trapdoor RAM chip. Oh well, need to find an adaptor now I guess.

Thanks for clearing that up guys.

I got the impression you want to add 512KB chip RAM, to make a total of 1MB chip RAM and nothing else, right? If that's so, no gary adapter required!

[toadnode]

Originally Posted by PeteAU

I got the impression you want to add 512KB chip RAM, to make a total of 1MB chip RAM and nothing else, right? If that's so, no gary adapter required!

Yes Pete that's correct, trying to get a total 1MB chip RAM on a rev5 A500 with an 8372a Agnus.
Your first comment was "How you described the jumpers sounds all good and correct"... does that still stand given I'm not using a Gary adaptor?

I actually did install the card prior to the Agnus upgrade + motherboard mod and found no extra mem present then either, I think there should have been 0.5MB slow at that stage.

[hooverphonique]

Originally Posted by toadnode

I actually did install the card prior to the Agnus upgrade + motherboard mod and found no extra mem present then either, I think there should have been 0.5MB slow at that stage.

The OE 0.5MB slowfast from trapdoor is only present with EXRAM connected through - this is the signal that is normally used to disable it (using e.g. a toggle switch).

[Mathesar]

Originally Posted by toadnode

Yes Pete that's correct, trying to get a total 1MB chip RAM on a rev5 A500 with an 8372a Agnus.
Your first comment was "How you described the jumpers sounds all good and correct"... does that still stand given I'm not using a Gary adaptor?

I actually did install the card prior to the Agnus upgrade + motherboard mod and found no extra mem present then either, I think there should have been 0.5MB slow at that stage.

Sorry about the confusion then . I was under the impression that you wanted the fast+slow ram expansion.
If you only want 512kb extra chipram using a 8372a Agnus you dont need the gary adapter and your jumper settings are indeed correct.

[toadnode]

No worries.... Well I have a Gary adaptor in the mail now, at least I know what to do with my jumpers/EXRAM if I end up using it. Just be happy to get 512KB extra anything for now.

I've resoldered my RAM but still not seeing it