Ancient Amiga hackery showup: Bacterio's A4000 64MB Fast Ram mod

lostrego

Member
AmiBayer
Joined
Apr 4, 2011
Posts
706
Country
Spain
Region
A Coruña
Hi all:

I want to open this little thread to document an old achievement done by an Spanish technician on the late 90's, whose nick was Dr. Bacterio, sadly the source code can be considered almost lost as it was never released to the public.

As a fellow Amibay member developed his own variant from scratch (see here) It may be useful for further reference.




Here we go, the beast itself:

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Next, in detail view of Ramsey pull ups and cut circuit tracks, Note the Ramsey pinns 45 46 are wired to two pullups an the to pin 47 (Ramsey A24 and A25 signals wired to A26) :

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Back side, left wire is soldered directly to a track there that was not traced by us yet, right side wire is passed thru a via to underneath the GAL:

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Thru via wire goes there on the GAL chip:

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Detail of back side SIMM banks wire bridges and pull-up, if my notes are ok to pins 19 and 29 on the simm banks (must be signals A10 & A11 on the SIMMs):

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More detailed view of this:

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Final notes: This hack is somewhat restrictive in memory configurations as once done only two memory configurations are allowed and both fully autoconfig:

1) The traditional 2X8MB double sided SIMMs to get a total of 16MB (as any other A4000 can do by default).

2) The extended one using 4X16MB single sided SIMMs to get a total of 64MB.

Other configurations are forbidden.


Finally I want to thank two fellow members here than were lately trying to figure out and document more things about this old hack but due to lack of time nothing more was done:

Debvgger (who is also the author of the Pics, used with permission) and Crumb who along me tried to give some more light and unveil a bit more about this epic old achievement.

Hope you'll find it useful. :)
 

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Last edited:
nice.. this looks like it's basically the same as meutoxo's mod.. the simm A11 connection suggests that it also supports something to do with 64MB simms, maybe just to support them being used as 16MB simms, in which case I would think the wire would go to ground or VCC.
 
nice.. this looks like it's basically the same as meutoxo's mod.. the simm A11 connection suggests that it also supports something to do with 64MB simms, maybe just to support them being used as 16MB simms, in which case I would think the wire would go to ground or VCC.


Yes, only seems to differ in the gal's pins and in the second wire to the simms.
Nice post, thanks for the pictures.
 
nice.. this looks like it's basically the same as meutoxo's mod.. the simm A11 connection suggests that it also supports something to do with 64MB simms, maybe just to support them being used as 16MB simms, in which case I would think the wire would go to ground or VCC.


Yes, only seems to differ in the gal's pins and in the second wire to the simms.
Nice post, thanks for the pictures.


Thanks. (y)

Yep , the A11 I've not found yet where it was exactly soldered to on the mobo as the track was difficult to trace, one end goes to a via under fat gary.

And the other end, on the via where is the cable soldered on, it goes to the upper side of the mobo to a track that again is routed thru another via to the bottom side, and finally it leads to a last via that I suspect is located on the bottom side of U703 IC (next to super buster and SIMM banks).

However I haven't my A4000 dismantled to trace it more carefully or test if it's ground or VCC, I've done it following pictures of the mobo.
 
There is actually 64MB RAM patch done for me. And I will be running a A3660. No problem. But we should be looking forward to a 'native' memory expansion for the A3660 itself.
Anything other is just wasted memory speed...
 
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