das9674@usl.edu (Stephenson Daniel A) (04/07/91)
I've read this newsgroup fro a while now concerning the Smith Corona 32K cards. I know something weird happens when the calcs batteries get low, and that they sell for about $30 (nice). But, What exactly happens if the calcs batteries get low? is there a way to tell when your batteries are dangerously low? All possible problems considered, SHOULD I buy one?? I kinda need one, but the HP brand is SOOO expensive! Also, if I for some reason found a relatively cheap HP 32K brand card, HOW much cheaper would it have to be before its somewhat higher cost would be worth avoiding the low battery problem. I read this group always, so please post your thoughts, or E-mail me. Thanks! Dan Stephenson ph. (318)-231-4824
darrylo@hpnmdla.hp.com (Darryl Okahata) (04/08/91)
In comp.sys.handhelds, das9674@usl.edu (Stephenson Daniel A) writes: > I've read this newsgroup fro a while now concerning the Smith Corona > 32K cards. I know something weird happens when the calcs batteries > get low, and that they sell for about $30 (nice). But, > > What exactly happens if the calcs batteries get low? is there a way > to tell when your batteries are dangerously low? This really needs to be part of an FAQ list .... If you're unlucky, and the battery gets low, you can damage your calculator (this isn't guaranteed to happen, but it's a definite possibility). I've included some copies of old messages that describe how/why. -- Darryl Okahata UUCP: {hplabs!, hpcea!, hpfcla!} hpnmd!darrylo Internet: darrylo%hpnmd@relay.hp.com DISCLAIMER: this message is the author's personal opinion and does not constitute the support, opinion or policy of Hewlett-Packard or of the little green men that have been following him all day. =============================================================================== From steveh@hpcvra.CV.HP.COM Fri Mar 1 17:00:00 1991 From: steveh@hpcvra.CV.HP.COM (Steve Harper) Date: Thu, 10 May 1990 22:46:09 GMT Subject: RE: HP48SX Memory Card Pricing Organization: Hewlett-Packard Co., Corvallis, OR, USA Status: RO There has been a substantial amount of comment regarding the memory cards for the HP48SX and their prices. My purpose in this response is not to attempt to justify any particular price, but rather to present the technical reasons why there is a substantial price difference between the memory cards and other types of expansion memory for PC's, for example, with which users are probably more familiar. Some users have correctly pointed out that the memory in the cards is static RAM rather than dynamic RAM commonly used in PC's. Dynamic RAM uses one transistor and a capacitor for each bit of memory whereas static RAM requires either four transistors and two resistors, or six transistors. The net result is that an equivalent amount of static RAM is much larger and therefore much more expensive than dynamic RAM. The advantage is that static RAM doesn't need to continually be running and drawing current (refresh cycles) to retain the contents of memory. In addition, the static memory used in the cards is not just any static memory, but is specially processed and/or selected for very low standby current. This allows the backup battery in the card to keep memory alive for a very long time, rather than requiring the user to replace it every few months. The special processing and/or special testing to select low current parts adds to the already higher cost of the static RAM chips. The standard molded plastic DIP package used for most integrated circuits, including memory chips, is relatively inexpensive because of its simplicity and the huge volumes. Unfortunately, these packages are too large to put into a memory card. Therefore, the card manufacturer mounts the individual silicon memory chips directly on a special thin PC board together with the memory support chips. Because multiple chips are being placed in a single hybrid package in a special process which has lower volume, yields are lower and this again causes the cost to be higher. Indeed, the yield becomes exponentially worse as the number of chips and interconnections increases in such a packaging process. In addition to the memory chips themselves, two more integrated circuits and several discrete components are required for power and logic control. A bipolar technology chip senses the external voltage and switches the power to the chips from the internal keep-alive battery as needed. A CMOS gate array chip protects the memory address and data lines from glitches/ESD when the card is not plugged in. This chip also generates the proper enabling signals when there are multiple memory chips in the card, as is presently the case with the 128 Kbyte RAM card. These chips must be designed for extremely low current, just as the memory chips are. In addition to the battery and the battery holder, the other mechanical parts are important, too. The molded plastic frame holds the PC board and provides the foundation for the metal overlays and the shutter-and-springs assembly which protects the contacts from ESD and from contaminants. The write-protect switch is also an important feature. It is quite expensive for the manufacturer to make the tools necessary to fabricate each of these parts as well as the tools to assemble and test the complete card. While the volume of memory cards is relatively low this tooling cost represents a significant part of the cost of each card. Admittedly, there are other alternatives, such as those presently used in PC's, to provide a memory expansion capability. To provide that kind of expansion would require the calculator to be much larger than it is and possibly more expensive. This is clearly very undesirable. Other features that were felt to be essential were the ability to distribute software applications and to share and archive/backup user-created programs and data. Other expansion alternatives do not provide these important benefits. The IO capabilities of the calculator provide these features only to a limited degree. One other item bears repeating here: Memory cards for use in the calculator will clearly indicate that they are for use with the HP48SX. Other memory cards exist which are mechanically compatible with the HP48S, but these cards cannot be relied upon to work electrically in the calculator. The HP48SX cards are designed for a lower supply voltage range. Use of the other cards may cause memory loss, and under certain circumstances may even damage your calculator electrically. From steveh@hpcvra.CV.HP.COM Fri Mar 1 17:00:00 1991 From: steveh@hpcvra.CV.HP.COM (Steve Harper) Date: Fri, 11 May 1990 16:52:07 GMT Subject: Re: Memory Card: Give Us *True* Facts! (Was Re: HP48SX Memory Card Pricing) Organization: Hewlett-Packard Co., Corvallis, OR, USA Newsgroups: comp.sys.handhelds Status: RO My previous statement that under certain circumstances the calculator may even be damaged electrically is not a ploy. If the calculator's internal power supply voltage happens to be near the low end of the range, say 4.1 V, and the voltage at which the card's voltage control chip shuts it down happens to be near the high end of its range, say 4.2 V (this can and does occasionally occur for the non-HP48SX cards), then the calculator will start to drive the memory address lines and the card will still have these clamped to ground (that's what it does to protect itself when there is not sufficient system voltage to run). This unfortunate situation may simply trash your memory, or if the calculator tries to drive enough of the lines high at the same time, several hundred milliamps may flow...for awhile that is, until something gives up... On the other hand, your calculator and a particular non-HP48SX card may work just fine if those voltages happen to be at the other end of their ranges. These voltages are also slightly temperature sensitive. It may work in the classroom or office and not at the beach, or vice versa. The voltage trip point of the HP48SX cards has been set lower (a different voltage control chip) so that this cannot occur, regardless of part and temperature variations. One other item was brought to my attention yesterday by Preston Brown that I should have included in my original posting here. While most of us recognize that comparing ram cards to a handful of dynamic ram chips to plug into your PC is apples and oranges, it may be more interesting to compare the HP48SX cards with cards for other products, like the Atari Portfolio, the Poquet, the NEC Ultralite, etc. I believe you will find that the prices on the HP48SX cards are not at all out of line. Steve "I claim all disclaimers..." the non-HP48SX cards From prestonb@hpcvra.CV.HP.COM Fri Mar 1 17:00:00 1991 From: prestonb@hpcvra.CV.HP.COM (Preston Brown) Date: Thu, 17 May 1990 17:26:53 GMT Subject: Re: Memory Card: Give Us *True* Facts! (Was Re: HP48SX Memory Card Pricing) Organization: Hewlett-Packard Co., Corvallis, OR, USA Newsgroups: comp.sys.handhelds Status: RO When the RAM cards detect that voltage is to low to operate they clamp the address lines to ground. This clamping is done by turning on the output drivers of a custom chip included on the card. The clamping current is speced at 2mA min at the Vol output level. Since the 48 can be trying to drive the line all the way high even more current is typical. 10mA per fight is not uncommon with totals of several hundred mAs. The VDD power supply is regulated at 4.1 - 4.9 with typical parts at the low end (4.3). The power to the cards is switched thru a transistor, creating up to a 0.1V drop. Standard Epson cards have a significant chance of seeing this voltage as to low and shutting down. We have seen cards do this in the lab. When it occurs the calculator locks up with VDD pulled down to about 2.5V and 250mA being drawn from the batteries. This current drain greatly exceeds the ratings for the power supply and can dammage your calc. The least that will happen is a loss of memory. Now, why didn't we regulate VDD higher? The 48 has two power supplies VDD at 4.3 and VH at 8.5. VH cannot be regulated higher without exceeding the spec for our CMOS IC process. VH is used as the + voltage for the I/O. In order to meet a +3V output level VH must be more then 3.6V above VDD. (VDD is used as I/O ground). Our power supply system increase the battery life and reduces the cost greatly for the wired I/O. Preston
dave@bgtys6.uucp (Dave Hubert) (04/09/91)
In article <28577@rouge.usl.edu> das9674@usl.edu (Stephenson Daniel A) writes: > > I've read this newsgroup fro a while now concerning the Smith Corona 32K cards. >I know something weird happens when the calcs batteries get low, and that they sell for about $30 (nice). But, > >What exactly happens if the calcs batteries get low? is there a way to tell when your batteries are dangerously low? > > >All possible problems considered, SHOULD I buy one?? I kinda need one, but the HP brand is SOOO expensive! Also, if I for some reason found a relatively cheap HP 32K brand card, HOW much cheaper would it have to be before its somewhat higher cost would >be worth avoiding the low battery problem. I just got a bat(s) warning on my calculator which means the calculator batteries were low. I have 2 smith corona cards in my calc, 1 merged, 1 independant for backup. I replaced the calc's batteries with no problem. As to your second question, I don't think there such a thing as a relatively cheap HP 32K brand card. Everything is relative, unless your $rich. -Dave. PS. Anyone know of any cheap 128K ram cards? As compared to HP???
HCLIMER%UTCVM.BITNET@CUNYVM.CUNY.EDU (Harold Climer) (04/13/91)
Do you think that as production increases on the RAM cards,and more units are s
old that the unit price will come down as did the prices for the HP41CV/CX.
It seems to me that the prices for what I call the HP "BASIC" products ie the
calculators come dow much quicker than the accessories. Good deals can be had
for the calculators but pay through the nose for accessories. Example the
overlay kit for the 48. Not near as good or as useful as the one for the
41 and $16.95 too.
Harold Climer