U009@CCIW.BITNET (09/12/89)
Back in early May, I purchased and installed a Datafree Industries 4 MB upgrade card into my (old) 1040 ST. The installation went more-or- less ok (minor problem with the pins and connectors size and orientation on their card- 1 phone call fixed that up quickly) and the memory diagnostics showed the replacement 4 meg worked fine. Since I use the system about 95% in the Mac emulation mode with a Spectre cartridge, I didn't notice anything wrong at all. I could read and write floppies (Spectre and Mac format with a Translator-1) without problems. It appears, however, that there is a problem on the Atari side under GEM. If I try to copy files to the floppy, the system will most often re-boot (like I hit the RESET switch) at some point during the first file. I checked the +5 Vcc at the cartridge port and found it drifting around somewhat, depending on what the machine was doing. When idle in the desktop, 4.85V, floppy operations, 4.79 to 4.92, Power on (memory test?) between 5.0 and 4.95V. Voltage at the power supply itself remains relatively constant, indicating a current related voltage drop in the wires or on the traces of the board. I was considering several alternatives: adding parallel wires for some of the heavy current traces (if only I knew which they were: I know! I'll do 'em all!), adding wire from the PS to the other ends of these traces, or, if the power supply is really drooping, stealing a little of the +12V, thru a resistor, to the 5V supply to boost the current limit. (We used to bypass the IN to the OUT terminal on 3 pin regulators with 10 to 100 ohms to help it in cases where we wanted 1.5 amps from a 1 amp regulator but I'm not sure if the same technique would work on the switcher inside the 1040.) Is there a low-power sensor and trap implemented (NMI or something) in the ST causing this problem? What is the nominal operating Vcc of the various chips in the ST (I don't suspect the memory has any problems at slightly reduced voltages but what about margins on the others?). Any suggestions would be most welcome. (And soon: my wife wants those games I just downloaded!) Regards, Stu Beal, VE3MWM, (U009@CCIW.BITNET), National Water Research Institute, Burlington, Ontario, Canada.