add 1 MB onboard ram to A500 Revision 6A MB

[klx300r]

I had an old mod article that basically said you just had to add 4 more 256 dram chips to the board but I'm not sure if I have to modify any jumpers/ cut traces etc? also I understand that this onboard ram will interfere with the additional 512K on the trapdoor A501 and possible the clock??

anyone done this mod or knows where I can find some info on it?? I found the dram chips and hope to get the ol soldering iron going again soon
 ;-)

[klx300r]

hey thanks im gonna try this out & keep my fingers crossed ;-)

[klx300r]

ok please let me know when/if you find that old article as my soldering hand is getting itchy :-)

[klx300r]

thanks for the reply but the link is dead :-?

[klx300r]

Tenacious wrote:

If you have 1 Meg of chip (512K on the mb and 512K on the A501), whats the advantage of moving it all to the mb?  You still need the RTC.  If you add another 512K (1.5 meg total) with some kind of glue logic, that 512K wont be true chip nor true fast memory.

You probably know this, but Supra's 500 RX fast ram expansion is one of the best first moves you can make (if you're not going for a HD/ram combo).   I wish I had had one of these back in 1989!

I basically need the extra chip ram to help my create my own music samples and also when using sequencer and tracker programs...and of course a few games require at least 1 mb chip too ;-)  I already got a Supra 500 RX with 2MB fast ram installed along with a A590 with 2MB as welland a 2GB scsi drive....serves me just fine for my retro gaming and making music :-D

[klx300r]

Tenacious wrote:
I think I remember getting the plans from a magazine as well.  I did find a file on my HD that details a similar hack for the A2000. The URL was still in the file note.   I never tried this one since acquiring A2000s only a few years ago.

I didn't test this link: http://main.aminet.net/hard/hack/A2K_agnus_hack.lha

thanks for the reply but the link is dead :-?

[klx300r]

rkauer wrote:
http://www.savel.org/old/amiga/upgrade.html ...

 hey thanks im gonna try this out & keep my fingers crossed

[klx300r]

Tenacious wrote:
It would be interesting if rkauer's link will convert a NTSC A500 into a defacto A500+ (I came away from the link a little in doubt).  If it works, (and you have 2-Meg Agnus) then all you need is a European (1 meg) A501 mapped to the chip memory address space.

The mod I mentioned above puts all 2 megs on the motherboard, the A501 is retained for the RTC only and its memory is disabled.

The Aminet links are broken because the directory structure was consolidated.  The hardware hacks were moved under the docs.  aminet.net/docs/hard/A2K_agnus_hack.lha

Good Luck

ok thanks i'll check it out but I have a 8372A Agnus which is only 1 MB..i beleive the 8375 was 2 MB but im not sure

[klx300r]

Tenacious wrote:
@klx300r

You have 1 Meg of chip ram, right? Not 512K of chip and 512k of fast when the sidecars are all pulled off, right?

well right now without my sidecars I have 512 chip 512 fast but hopefully this mod will give me 1mb chip and  if I can still keep my RTK that would be great too :-D

[klx300r]

Zac67 wrote:
If you want to have 1 MB chip, the first thing you need is that your Agnus has to be able to handle it. Whether the 2nd 512K sits on an A501 or onboard does not matter a single bit.

With a 1 MB Agnus, you just change the A19 jumper and open the _EXRAM jumper, that's it.

whoooaaaaa  :-o ok (me shuts off soldering iron for now) now since I already have the 256 drams can I install them on the mb without any conflict  :-?

[klx300r]

Chain wrote:
http://eab.abime.net/showthread.php?t=31816

followed this thread and I'm more confused now then when I started out :-?  so did you ever get this mod to work to get 1MB chip soldered on board, 512k fast with RTC working fine on trap door on the Rev6A motherboard :-?

[klx300r]

Zac67 wrote:

Zac67 wrote:
Without somewhat severe modifications to the board, esp. Gary's address decoding logic, you can't use more than 1 MB chip/'fast' total.

Third try to explain:
You can't use the 2nd onboard 512K and the trapdoor RAM simultaneously unless you rework the addressing logic. If you don't understand what this is about, you won't be able to do it.

hey thanks for your help but I'm reading 10 different solutions from 20 different people worldwide :-?  so I guess now the safest bet is just to keep my trapdoor expansion slot and change a few jumpers to get 1MB chip I guess..i got enough fast ram with my supraram500rx and a590 anyhow :-)

say I already sucked the solder outta all the dram motherboard locations....is it safe to leave them open or do I have to resolder them closed??

[klx300r]

Zac67 wrote:
If you want to have 1 MB chip, the first thing you need is that your Agnus has to be able to handle it. Whether the 2nd 512K sits on an A501 or onboard does not matter a single bit.

With a 1 MB Agnus, you just change the A19 jumper and open the _EXRAM jumper, that's it.

change the A19 jumper to where :-?

[klx300r]

Tenacious wrote:
@ klx300r

You sucked the solder out of the MB?

Certainly, solder the chips back in.  Try to alternate between chips to prevent overheating any one of them.

Good Luck!

ya i initially was gonna solder 4 new 256 drams into the empty sockets on the 6a mb but now i'm gonna go on the safe route and just leave my 512 trap door expansion in and allocate that to chip ram so that i get a 1mb chip ram total an hopefully keep my RTC working...my supram500rx and a590 will take care of the fast ram.

saying that I understand I have to open jumper 7A and do something else to jumper 2..(can anyone confirm what I must do to jumper 2 please...i checked aminet with no concrete answers there...thanks for the help :pint:

[klx300r]

EXCELLENT :-D  Just finished the mod and it worked great !!! got a bit of a scare when I first booted it up & got greeted by a green screen but I troubleshooted the problem as being some extra flux on the board sooo after a good cleaning all was fine and peace was restored back in my Amiga land :lol:

thanks very much for your help :pint: