jonb@vector.dallas.tx.us (Jon Buller) (07/14/90)
Just a couple of quick questions as my board nears completion. Can +5V be applied without +12 and -12? And about how much current does it draw? It must be less than 2A, but that seems like a lot to me. And one other thing, does the monitor speak on any port that it gets some data, or on connector 3 first (or some other arrangement, and what speed too)? ---------------------------------------------------------------------- Jon Buller jonb@vector.dallas.tx.us ..!texbell!vector!jonb FROM Fortune IMPORT Quote; FROM Lawyers IMPORT Disclaimer;
dlr@daver.bungi.com (Dave Rand) (07/14/90)
[In the message entitled "pc532 power use" on Jul 13, 13:40, Jon Buller writes:] > Just a couple of quick questions as my board nears completion. Can > +5V be applied without +12 and -12? Yes - although you must connect the +/-12 before trying to use the board with a terminal. These voltages power only the 145406's (RS232 level shifters). > And about how much current does > it draw? It must be less than 2A, but that seems like a lot to me. The board running at 25 Mhz draws about 2.5 Amps of +5 (2.1 if you are using 2692 CMOS DUARTs). The +/-12 V supply only requires a few milliamps. Note that some switching power supplies will refuse to come up without additional load on the +12V rail - such as a disk drive. A typical IBM AT style power supply provides 20 to 25 Amps of +5, and 10 Amps or so of +12. -12 is usually 500 mA. Besides 2.5 A is about 12.5 watts - not back for a 12 MIPS machine! > And one other thing, does the monitor speak on any port that it gets > some data, or on connector 3 first (or some other arrangement, and what > speed too)? The monitor will talk on CONN3. Be sure to have _ALL_ of the DUARTs installed (or at least U60), as the 3.6864 Mhz clock is shared between all of the DUARTs. -- Dave Rand {pyramid|mips|sun|vsi1}!daver!dlr Internet: dlr@daver.bungi.com
jonb@vector.dallas.tx.us (Jon Buller) (07/14/90)
> The board running at 25 Mhz draws about 2.5 Amps of +5 (2.1 if you are > using 2692 CMOS DUARTs). The +/-12 V supply only requires a few milliamps. > Note that some switching power supplies will refuse to come up without > additional load on the +12V rail - such as a disk drive. A typical IBM AT > style power supply provides 20 to 25 Amps of +5, and 10 Amps or so of +12. > -12 is usually 500 mA. > > Besides 2.5 A is about 12.5 watts - not back for a 12 MIPS machine! Well put, I wasnt thinking of all that speed, memory, etc. (my projects are usually smaller. The modems I program at work draw about 150mA max. and my sound digitizer runs off my Mac's serial port drivers...) I got the 2A number by remembering the 2 1A fuses which power the SCSI busses not the board itself. But this tells me just what numbers to put into the power supply on the test bench before putting it in the pc case I bought. I'd much rather have my board pull 2.5A at 2V if I did something wrong rather than 20A at 5V and let all the smoke that runs everyting out of the system. I want to conserve all that magic smoke 8-) ---------------------------------------------------------------------- Jon Buller jonb@vector.dallas.tx.us ..!texbell!vector!jonb FROM Fortune IMPORT Quote; FROM Lawyers IMPORT Disclaimer;