Tabajara A601 memory expansion

[Chartus]

I think I will try this hack since I can't find a real A601 trapdoor expansion in the US.

Just a few questions.

1. Does it have to be FPM simms or can you use EDO simms instead ?
2. Can you use 30 pin simms instead?
3. Memory size doesn't matter?

If these are stupid questions feel free to laugh  ;-)

[Chartus]

Thats good news.  I think I will give it a try.  Now to go dig out them old 1 meg 30 pin simms.

[Chartus]

Quick question.  Do I have to use 30 pin SIMMS in pairs.   What I'm asking is do I need 1 or 2 SIMMS.

[Chartus]

Just one?  Looking at the 30 pin SIMM pinout it looks like there are only 8 data pins.  Dont I need 16 data pins?  Or do I just connect the first 8.

[Chartus]

That clears things up.  I will go with 2 1meg simms since I have some on hand.  Thanks for all the help.

[Chartus]

So just wire up the first 8 data lines?  I notice that the a600 trapdoor has 16 data lines.  Do I just leave the unused address lines N/C ?
 

[Chartus]

I have found an old 4 meg 72 pin simm (IBM)that I can use so I will probably go with that.  The fun part will be building it to fit in the trapdoor without taking the machine apart.

It will be a tight fit but I think I can do it.

[Chartus]

I haven't tried the 30 pin simms yet.  First I tried to get the 72 pin simm version to work.  Wired it up and the machine would boot but the memory count didn't change.  I looked at the russian papers and there is a difference in your A600 table and his.  I tried his but just kept getting yellow screens at boot.  I think I read that this was caused by chipmem problems.  I am not that great at soldering and right now I am sick trying to get this working.  Maybe I will try again later.  It might just be a bad stick of memory.

Hmmmm..... My first rant (I think)

[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.

[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.

[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.

[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.