Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!sdd.hp.com!hp-pcd!hpcvra.cv.hp.com!rnews!hpcvbbs!akcs.gak From: akcs.gak@hpcvbbs.UUCP (Eric Gakstatter) Newsgroups: comp.sys.handhelds Subject: Re: CMT RAM card - deficient? Message-ID: <27c1b440:1758.9comp.sys.handhelds;1@hpcvbbs.UUCP> Date: 19 Feb 91 23:40:10 GMT References: <153@caspian.dde.uucp> <27aaf227:1758.8comp.sys.handhelds;1@hpcvbbs Lines: 76 In response to inquiries about CMT cards for the HP-48, CMT has released the following information pertaining to the power consumption and low-bat characteristics: The SRAM cards have two power sources. The first of these is the battery that is installed in the card. The currents drawn from this battery are shown in Table 1. The other source of power is from the HP-48SX battery when the card is installed in the 48. The currents from this are shown in Table 2. TABLE 1 Card battery current of the HP 128K SRAM card versus the CMT 128K RAM card removed from the HP-48SX. Switch position is indicated as "READ" or "READ/WRITE". CARD READ CURRENT READ/WRITE CURRENT CMT 128K SRAM 0.2876 microamps 0.3003 microamps HP 128K SRAM 1.649 microamps 1.676 microamps TABLE 2 Current draw of the memory cards with 4.4 volts applied to the card and all address and control lines held at ground. This is close to the current draws that occurs when the card is installed in a HP-48 that is turned on. CARD READ/WRITE CURRENT CMT 128K SRAM 2.0 microamps HP 128K SRAM 845.0 microamps Assuming that the card is sitting on the shelf, Table 1 would be the current draw that is applicable. The batteries that are used in the card are 75 mA-hour batteries. Using this, the expected life of the battery in the two different cards is: CMT 128K SRAM -> 249,750 hours -> 28 years HP 128K SRAM -> 44,749 hours -> 5 years This isn't realistic because the lithium batteries decay by themselves in about 5 years. However, it does show that CMT's card battery will definitely last for two years and will probably last for 5 years. The extra battery life makes data stored in a CMT card more secure than the data in the HP card. Table 2 shows that the CMT card draws significantly less operating current than the HP card. This will result in a longer HP-48SX battery life. The HP-48SX low battery indicator works with the CMT cards if a battery is installed. Without a battery installed, the low battery indicator does not work. This is a side effect of designing the card for low power usage. We felt that the decrease in power usage was well worth the trade off. Based on these figures, CMT recommends that the battery in the card gets changed every 2 years. Since the power consumption is so low, CMT also recommends that the battery remain inside the card during storage and shipping. If there are any questions on this matter, please contact: Corvallis Microtechnology, Inc. 413 SW Jefferson Ave. Corvallis, OR 97333 503/752-5456 CMT is a firm believer that the customer should be fully informed of the products they are purchasing.