Tabajara A601 memory expansion

[AeroMan]

When I've saw this name I was pretty sure this was posted by someone from Brasil...  :-D  :-D

[Chartus]

@AeroMan:

Nope.  Born right here in the great state of Texas. Thats not my real name, just a nic.

@rkauer

Couldn't get the hack to work with my 4 meg SIMM (nothing but yellow screens) so tonight I tried a 2 meg SIMM that I know is good.  Soldered it up and double checked the wiring. Looks good so I installed it.  Turned on the computer and SAME YELLOW SCREEN .  Took it out and rechecked the wiring.  Still looks good, no shorts or incorrectly routed wires.  So I went back and checked the tables and reread your notes.  Wait.  I missed pin 67 on the A600 trapdoor.  What does it connect to?  I also have pin 75 grounded with a 470 ohm resistor.  

Does pin 67 make a difference in this hack?  Will too long wires cause problems.

[rkauer]

 A600's trapdoor pin67 is 14.3MHz from the motherboard. Not connected in the SIMM. It uses the RAS/CAS signals as clock.

 Pin #75 is not connected to anything! It have a 470 Ohms resistor internally on the A600 board!

 I simply put the description of the pin assigns on bellow the document for people willing to make his/hers/theirs own hacks!

 Remove the resistor, leaving the pin floating. Then try again.

 If still not working, use A600's CASx(0) instead of CASx(1). Explaining a bit better:

 Use pin 43 instead 46 : CASU(0) instead CASU(1)
 Use pin 45 instead 44 : CASL(0) instead CASL(1)

 Oh, BTW: I think Aeroman was talking about me. You didn't notice my accent?

 :-)

[Chartus]

Still doesn't work :boohoo: CASU0 and CASL0 doesn't work at all. :roll: I switch the lines around (using the CAS 1 lines) and sometimes I can get it to boot but the extra memory never shows up. Sometimes a green screen. Thats about all I can get out of it.  Maybe my expansion slot is defective.

Damn.... I hate whining like this.  This a600 is going to drive me to drinking.

[rkauer]

 Then some more hints. If don't work, drop it, your A600 motherboard revision may not work with the hack.

 BTW: what revision it is? 1.0 (A300)? 1.3 (buggy)? 1.5? 2B or 2D?

 Green screen means "almost good", the Amiga found the memory but wasn't able to configure it. Check the traces/wires, specially the address ones. And be sure to use a working SIMM, too.

 What speed is your SIMM? It must be 70~80ns (like the RAM chips on the A601 itself). Faster SIMM are no good, since they could not hold the information for enough time (too slow refresh rate from the Amiga).

[Chartus]

I am using a 70ns SIMM which I know is good. I just poped the top of the computer and I found out it is a revision 2B A600.

I wonder if the PCI slot is good enough.  I would install it and turn on the computer and it would boot but no extra memory. I would turn it off unplug it and plug it back in and turn the comp. on and it would green screen.  Maybe its too loose.  I am using the complete slot; I just pulled the extra wires out after the first 80 pins.  I have been carefull to plug it in at pin 1 though.

I will try it 1 more time with another 2 meg SIMM.  I think this one is 80ns and I will solder on both sides of the SIMM.  Last 2 times I soldered all on 1 side.  Do you think it wold help if I installed a capacitor on the 5v rails.  The SIMMS have them also.

If that doesn't work I will try to score some memory off of a video card and do the mode from EAB.  

Now to go look at my machine now that I have the cover off.  Maybe I will see something new.

[rkauer]

 You need the caps on the +5V rail! Without it the voltage ripple will cause bad behaviour (from the Amiga, you don't wanna attack grandmas).

 One 47uFx10V will suffice. Install it in the middle-most +5V contact. Measure the voltage level before and after the modification.

 If the PCI slot is too loose, it could be the cause of no-working hack. Try to tight it a bit using a small "hook" shaped tool.

[AeroMan]

rkauer wrote:

 Oh, BTW: I think Aeroman was talking about me. You didn't notice my accent?

 :-)

Yeap, for sure. "Tabajara" is such a magic word... :-D  :-D  :-D

[Chartus]

SUCCESS :lol:  :lol:  IT WORKS. :lol:  :lol:   I started over with a new PCI slot and shortened the wires.  It has been running for about 4 hours now.  Seems to be stable so I will let it run for a day or so straight.  I got it playing Empire against itself and that will take a few days at least.  If it acts up I will put a capacitor on the 5v  but I counted 16 on it already.  I was thinking about running 5v from the power plug to the SIMM; 16 chips might need a little more power. Just a thought.

If all goes well I will be able to start work on my trackball.  Thats next.  Now to look at WHDload.  I got a hard drive to fill up.

[rkauer]

 Congratulations!

 Is good to hear about someone who was able to do my hack!

 For filling the HD, I suggest you start from here.

 Classic Workbench for A600 (ECS) is very good and you will not regret it!

 You need to tweak it a little after the set-up, and need a 50Mb or more boot partition, but it is a superb start.

[Protek]

I'm keen on trying this memory upgrade myself, since I'm packed with 72 pin SIMMs dunno, whether they're EDO or FPM, though. Would it be possible to design and fabricate a PCB for this? I guess the available space is the limitation?

[rkauer]

Protek wrote:
I'm keen on trying this memory upgrade myself, since I'm packed with 72 pin SIMMs dunno, whether they're EDO or FPM, though. Would it be possible to design and fabricate a PCB for this? I guess the available space is the limitation?

 Yeah, the space for the hack is tight. Better stick with the "wired" version. Just keep the wires short enough and only use FPM SIMM. 70~80ns are the best for it.

 If you don't know if the chip is FPM or EDO, look directly on chip and Google for "code-of-the-chip datasheet alldatasheet".

 The http://alldatasheet.com is simply the best site for information on semiconductors!