How to connect a 2nd Harddisk to the NCR 3125: ---------------------------------------------- Important note: I assume no liability for any damage which may result from carrying out the below instructions. Everything you do is at your own risk! Prerequisite: The 1st harddisk which is already built into my NCR 3125 is a 2.5"-20MB- drive by Prairytech. It has a 2x50-pin-connector with a 2mm-grid and is a standard IDE drive. So the second fixed disk drive has to be connected parallelely, but it must be set to be the slave drive. This is normally done with a jumper. The slave drive can then be accessed as drive D in DOS and its parameters (user type, numbers of heads, sectors, Cylinders, Landing Zone and WP) have to be entered in the BIOS-setup as fixed disk drive 1 (the other is 0). Carrying out the modification: After having opened the Notepad and flipped the screen to the right, the board should look like this: +-----------------------------------------------------+ | +---------------+ +--------------+# | | | | | drive- |# | | | 2.5"-harddrive| | electronics |# IDE | | | | | |#connector | | +---------------+ +--------------+# | | # | | # | | option- # | | slot # | | # | | # | | | | | |power supply | +-----------------------------------------------------+ IDE-connector more detailed: 50--|# 48--|# 46--|# IDE pin 40 44--|# . 42--|# . 40--|# . 38--|# . 36--|# . 34--|# . 32--|# . 30--|# . 28--|# . 26 |# key 20 24--|# . 22--|# . 20--|# . 18--|# . 16--|# . 14--|# . 12--|# . 10--|# . 8--|# IDE pin 2 6 4-- 2-- The connector has two rows, here is only shown the upper one with the even numbers. Pins 1 to 6 of the drive electronics are not connected. The standard IDE-connection has only 40 pins, so pins 47 to 50 are additional, probably for the power supply. The pin numbers printed on the drive-electronics-board and those of an IDE-cable are not the same, they are shifted by 6. You have to connect all IDE-signals (1...40) to the external drive. I have wired them from the built-in drive to a new connector on the left side of the Notepad under the unused flap. Unfortenately, there is not enough space left to close this flap, so I have left it out. I can now plug in a standard IDE cable such as those of a normal desktop PC. The required connector has 2x40 pins in a 2.54mm grid. A good way to do the wiring is to connect the lower (odd numbers) and the upper (even numbers) row seperately. I have taken two 21cm long ribbon cables and soldered the right ends directly to the drive electronics of the 2.5"-drive. The 20 odd number wires are lying below the 2.5"-drive, the even number wires above. You will have to remove the drive first. Here's a side-view: male /------upper 20 wires (IDE 2..40)-----------\ female IDE / \ IDE- conn. / +---------------------+ +------drive----------+-\|# connector ---\ / | 2.5"-harddisk |==+-----electronics-----+-/|# on mother- ---/ \ +---------------------+ / board \ / \--------lower 20 wires (IDE 1..39)---------/ Note that the upper and the lower cable-layers have to be crossed, if you use a male IDE connector. This is because a normal IDE cable which can then be used has female connectors at each end. If you are not shure about this, follow the IDE signal 20 which is left out at a hard-drive and is labeled "key". However, pin 1 is always located at the side near the option slot. Normally, an IDE-cable has a red cable as number 1. The last thing to do is the power supply. I have first taken the +5V and the +12V from the option-slot (which is 95% the ISA bus). This worked, but I didn't have a good feeling with this. My 3.5"-HD consumes about 500mA/5V and 200mA/12V. I am now using an additional power supply, but plan to build one powering both the Notepad and my 2nd HD. The following pinout diagrams are taken from a hardware-FAQ-file: (Power Connector) Male __________ / \ | 4 3 2 1 | ------------ Power Connector Male pin assignment 1 +12V 2 +12V return 3 +5V return 4 +5V IDE Hard Disk Interface IDC-40 Male pin assignment pin assignment 1 -Reset 2 GND 3 Data 7 4 Data 8 5 Data 6 6 Data 9 7 Data 5 8 Data 10 9 Data 4 10 Data 11 11 Data 3 12 Data 12 13 Data 2 14 Data 13 15 Data 1 16 Data 14 17 Data 0 18 Data 15 19 GND 20 Key 21 (reserved) 22 GND 23 -IOW 24 GND 25 -IOR 26 GND 27 IO Chrdy 28 Ale 29 (reserved) 30 GND 31 IRQ14 32 -IOCS16 33 Addr 1 34 (reserved) 35 Addr 0 36 Addr 2 37 -CS0 (1F0-1F7) 38 -CS1 (3f6-3f7) 39 -Active 40 GND Well, I hope, that I didn't forget any essential information. Finally I want to tell you about a problem I have run across with my 3.5"-drive: The power saver of the BIOS switches off both drives at the same time. If one of the drives is going to be accessed, drive D is turned on again first, drive C second. As my drive D seems to be rather slow, this takes 10 seconds! Another problem is that sometimes the computer locks after the drives are on again. I do then have to turn off and back on the 3.5"-drive and press the reset button of the Notepad. I hope that this becomes better, when I have built my new power-supply. [Yes, it became better.] That's all. If you have any troubles or don't understand my poor English, please email me: kspeichl@cip.e-technik.uni-erlangen.de Good luck and have fun! Klaus