256k -> 512k Ram Upgrade

[classics]

I'm looking at the instructions for adding another 256k to an existing 256k upgrade here:

 

http://atrey.karlin.mff.cuni.cz/~pavel/atari/800xl512K.html

 

It requires a 74LS139 and all the connections seem ok, except that it feeds pin 12 (O0B) back into pin 3 (A1a).

 

The problem is that the inputs for O0B are pins 13, 14, and 15.

 

Pin 13 is tied to ground, pin 14 is a signal taken from the original upgrade, but pin 15 of the 74LS139 is never connected in the instructions. Has anyone actually done this upgrade?

 

Steve

[kenfused]

I'm looking at the instructions for adding another 256k to an existing 256k upgrade here:

 

http://atrey.karlin.mff.cuni.cz/~pavel/atari/800xl512K.html

 

It requires a 74LS139 and all the connections seem ok, except that it feeds pin 12 (O0B) back into pin 3 (A1a).

 

The problem is that the inputs for O0B are pins 13, 14, and 15.

 

Pin 13 is tied to ground, pin 14 is a signal taken from the original upgrade, but pin 15 of the 74LS139 is never connected in the instructions.  Has anyone actually done this upgrade?

 

Steve

859495[/snapback]

Did you do this line?:

 

"Attach another wire between pin 2 of the 74S139 and pin 17 that you lifted

on U23, the 40 pin PIA."

 

This has you connect PB7 from the PIA to a GND which seems wrong. I tried to get it working in '95 but kept failing (never was stable). But looking back at my usenet post I had swapped a couple pins (assuming the diagram matched what I did). I also labeled the chip wrong in the diagram.

 

so maybe try attaching the wire from pin 15 to the pia pin that was lifted.

Half of the circuit looks like it is intended to not enable the selft test when PB7 is low and you are in the second bank. The other half selects between the two ram banks.

[JR>]

I don't remember where I found this but amybe it will shed some light on your problem.

 

 

The 512k XL upgrade that works rev:2.b NOV 27/2002

Revised by Guy Ferrante -Atari8man-

 

 

 

 

First of All I would like to Thank Jeff Worley (Technoid Mutant) and Shannon Robbinson (Doctor Death) for Helping me Fix the 512k XL upgrade. Without there Help the 512k XL would not work at all.

 

**** Many thanks to Mathy van Nisselroy! he has encourge me to release this upgrade. ****

 

There's a 512k XL upgrade on the Internet at the British Underground web-site that dose not work, I tried 3 times and even spoke about that upgrade to Bob Puff (CSS) and he told me that he to could not get that upgrade to work either. I was ready to give up on the idea of having a working 512k XL but thought I would start researching the darn problem, and by talking to other's that have tried to fix the upgrade. Well after a few months of fooling around with it and gathering notes from other people, the Problem with the 512k XL was fix for good!

 

I then sent the XL to Atari Classic magazine for review, The Publisher Ben P. had a Ball testing the XL and Told me that its was the most XE compatible XL he has ever seen! and that he wanted to publish the upgrade in Atari Classic. Just a few weeks Later Jim Hood passed away and Bob Wooley took over Atari Classic, and the upgrade was never published.

 

 

NOTE: You must know how to read the pins on ic's and have some soldering skills to do this

Mod, if you smoke your XL's or yourself tobad. You can allways

find someone that will do this simple upgrade for you at any Atari user club.

 

When your done with this upgrade you will have a perfectly working 512k XL thats

more compatible with the XE than just the stocked rambo, a 448k ramdisk and that 10 second (rambo) delay is gone for good! you can now turn your computer on/off without counting to 10! Sparta dos and Mydos work perfect with this mod, Sparta dos-X recongnizes 320k of it, ICD never release enough info on SDX sorry. So if you want to use all the Ram use any binary version of Sparta dos and Mydos 4.5

 

 

First of all you must have a perfect working 256k Rambo or Claus Buchholz computer and you will need these parts:

 

256k Dynamic Rams (150 ns or better)

1) 74LS139

1) 33 ohm resistor 1/4 watt, but 1/2 watt will work also

1) Spool of wirewrap

 

 

INSTRUCTIONS: Open up your computer and remove the 8 ramchips then install the new ramchip and do a memory check to be sure that the new rams are ok and test fine. If they test good then remove them to. Now bend out pin 15 on 8 of them, clip in half all the pins you bend out. now you must pigyback the chips with a bend pin 15 ontop of the 8 chips that do not have a bent pin 15 and solder them together. Now replace the rams into the computer and daisy chain all the bend 15 pins together with hookup wire.

 

 

Bend out all the pins, except pin 8 and 16 on the 74LS139. clip in half all the pins you bend out. Now solder a small wire between pin 15 and 8 and another short wire between pin 3 and 10 now clip one lead on the 33-ohm resistor to 1/4 in lenght and solder it to pin 7.

 

Now locate the PIA (u23) part # CO14795 and bend up pin 17.

 

Locate R108, a 33-ohm resistor there are 2 immediately below the row of ram scockets on the board, heatup the inside end and pull it up (This resistor gose to pin 15 on the lower banks) so use a multi-tester to find the correct one.

 

Now solder pin 8 and 16 of the 74LS139 to any 16 pin chip on the motherboard I use u28 but there are others to use, this provides power to the 74SL139.

Now solder a wire from pin 1 on the 74SL139 to the pad where you just removed 1 lead of R108.

Now Solder a wire from pin 5 on the 74SL139 to the lifted lead of R108.

Now Solder a wire from the resistor on pin 7 of the 74SL139 to pin 15 on the top row of rams (the daisey chain)

Now Solder a wire from pin 11 on the 74SL139 to pin 6 on the MMU pal (U3 part # C061618) this use to be connected to pin 17 on the PIA before you pulled it up.

Now Solder a wire from pin 13 on the 74SL139 to pin 17 on PIA.

Now Solder a wire from pin 14 on the 74SL139 to pin 14 on the rambo 74SL153 (IC2)

Now Solder a wire from pin 2 on the 74SL139 to pin 2 on the rambo 74SL153

 

---------------------------------------THATS IT your done!-------------------------------------------------------------

 

Test the computer and if it works fine use HOT GLUE to tack down the wires.

 

If you computer dose not turn on then check for shorts and solder bridges you may have made and try again.

I have build 30 or more of these upgrades for Atari users with out problems.

 

NOTE: Best computer sell the Wiztronics 256k upgarde, there are problem when doing this mod on it.

It will work but puts lots of RF on the screen. Use Rambo or the Claus Buchholz ONLY!!

I will fix the Wiztronic problem at a later date.

 

Mydos user:

 

Here's what you need to do to setup the ramdisk:

At the Mydos menu press o

Drive number (return) enter nothing

Verify writes (y/n as you wish)

Number of file buffers (as you wish)

Ramdisk present? Y

[A]xlon or [X]E type? X

Use default config for 448k Y

 

Use Option H to write dos back to disk with the new configuration and reboot.

 

 

EXTENDED MEMORY BANKS:

 

EF EB E7 E3 CF CB C7 C3

AF AB A7 A3 8F 8B 87 83

6F 6B 67 63 4F 4B 47 43

2F 2B 27 23

 

Bits used of Port B - 765432

 

 

 

---Things to look for in the Future that we are working on---

 

320k XL even more compatible with the XE than the 512k XL! by (Atari8man) Comming soon

A revised Claus Buchholz compatible upgrade by (technoid Mutant) code name (Sly Stalone!) (done)

MIO Clone (1 meg version) in the works 75% completed

256k Ramcart (done) will soon be for sale

 

 

If you Need help with this mod I can be found on the CTH BBS or comp.sys.atari8bit newsgroup

 

guyferrante@cfl.rr.com

Atari8man9@netscape.net

 

[classics]

Thanks for the replies guys. If hooking up the PIA as the enable doesnt work I will try the revised instructions.

[Almost Rice]

Will this work with a Newell upgraded 800xl?

[Almost Rice]

Just to let everyone know. If you have a Newell 256k 800xl, there is a mod to make it Rambo compatible.

 

here's a link

 

I guess after doing this you can use the 512 upgrade above. I may do just that since I have a set of 256k chips.