tlz@druxu.UUCP (ZrustTL) (01/16/86)
I ran across an article someone got from Compuserve recently on how the soon-to-be released ROMs should be installed in the 520ST. As I was installing my 68 ohm resistors (yes, I'm paranoid) I thought I would see if my machine's ROM wiring matched what was stated in the Compuserve article by Keith Hope of Batteries Included. It doesn't. In all fairness to Keith (who I'm sure had a different vintage machine or something) the article mentions very early that any deviation in wiring in the machine the reader is upgrading from what was in the article would render the article unapplicable. He's right. Let me give some examples: > There should also be a jumper wire running from pin 3 of resistor > pack RP2 to a solder pad in the notch of socket U3. If not, your > on your machine is different than mine and you are on your own! No jumper on my machine. > Mark and remove the two EPROMS from sockets U4 and U7. Store them > in anti-static material. I've got two mask programmed ROMS in U4 and U7. > Install the 4 bypass capacitors in locations C1, C2, C4, C7. This > may require that the joles be desoldered first. C1, C2, C4, C7 are already on my board. > Remove the jumper from RP2 and U3. No such jumper on mine. > Remove the solder bridges from the underside of the EPROM sockets > joining pins 27 & 28. This is important! Check for solder splatter > and make sure that the pins are still properly soldered to their > own pads. No solder bridges on any pins of any of the sockets on my beast. Does this sound redundant? > Carefully jumper pin 3 of RP2 to pin 27 on all 6 EPROM sockets in > a daisy chain fashion. This finishes correcting the alterations > Atari makes to the board so they can use a pair of 2764 EPROMS > instead of the 27256's the board was made for. Ah ha! This is the root of the confusion! My board has ROMs, his had 2764's. This probably explains everything! The only thing I forgot to do was to check continuity between RP2 pin 3 and pin 27 of the sockets. I'll bet that connection is already there, too. My guess is that my system has ROMS with 27256-like organization (same as the final ROMS) and has all the right stuff already in it. The article continues with parts locations, etc. but the point I wanted to make was that perhaps on machines such as mine the ROM installation may be as simple as yanking out the two old ROMs and sticking in six new ones (in sockets no less). Wow! If you are reading this and really know what the installation process is for MY machine, please let us all know. -- Terry Zrust AT&T-ISL Denver, CO (303) 538-4547
stone@calgary.UUCP (Glen Stone) (01/17/86)
> > The article continues with parts locations, etc. but the point I > wanted to make was that perhaps on machines such as mine the ROM > installation may be as simple as yanking out the two old ROMs and > sticking in six new ones (in sockets no less). Wow! > I'd just like to comment that when I upgraded to one meg I noticed that the two ROMs currently installed had what looked like DIODES ( zeners ??) across power and ground. The empty sockets did not. Will these have to be added ?