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Poqet PC Mailing List Digest
Volume 002, Number 010, 5 Sep 1997

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  1. SRAM, Flash, SunDisk, etc. by john s mercer <jmercer@xxxxxxxx>
  2. Re: Digest poqetpc.v002.n009 by Michael Fetterman <d005041c@xxxxxxxx>
  3. Re: Digest poqetpc.v002.n009 by Michael Fetterman <d005041c@xxxxxxxx>

Digest Articles

SRAM, Flash, SunDisk, etc. by john s mercer <jmercer@xxxxxxxx>


From: john s mercer <jmercer@xxxxxxxx>
Subject: SRAM, Flash, SunDisk, etc.
Date: Thu, 4 Sep 1997 23:22:27 -0400 (EDT)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
In-Reply-To: <199709042101.OAA20411@xxxxxxxx>

Bryan's explanation of the different cards is terrific: educational,
entertaining, and practical.

I have had a good deal of experience using an Atari Portfolio with a Flash
card.  When that card is nearly full, one needs to run a process freeing
memory since when you update or delete files they are not actually
erased, except by this special process.  It really is not as cumbersome as
it seems.  I remember just having to run the memory-freeing erase process
every couiple of weeks.

To trasnfer files to and from the Poqet, I use an SRAM reader in my
desktop from, I think, EduCalc. (I can find the details if anyone needs
them.)  The reader and software cost about $75.00 and work like a charm.
It's a painless and rapid way to transfer files, to keep data up to date
on both machines, and to back up the Poqet data.  For instance, I use
Brown Bag software's excellent PC-Outline to keep to do lists, goals
lists, phone lists, and addresses.  It turns out that I like it so much on
the Poqet that I use the same system on the Desktop, running it off the
SRAM card.  On the Poqet I also use AS-EASY (a Lotus 1-2-3 clone) for
expense reporting, for billing, and for class lists and use Eric Meyer's
excellent VDE editor for writing (I have been using various versions of
VDE since my Osborne 1 arrived in the early 1980's). With the card reader,
I can make a back-up of all informaiton on a one meg card almost
instantaneously; it's amazing.

But there is a rub to all this.  When traveling in South America recently,
I ended up hauling along a much heavier laptop since there was no easy and
reliable to transfer information from the Poqet to machines in the
offices where I was working.  I guess I need a Poqet floppy drive as well,
for such trips.  (I remember, with a good deal of pain, transferring data
from my Tandy 100 to other machines through serial cable.)

Having gone on at such length, I might as well ask if anyone has any two
meg SRAM cards for sale or could tell me where to get a couple.  I'm sure
I wouldn't need them if I were more concise.

John Mercer






Re: Digest poqetpc.v002.n009 by Michael Fetterman <d005041c@xxxxxxxx>


From: Michael Fetterman <d005041c@xxxxxxxx>
Subject: Re: Digest poqetpc.v002.n009
Date: Thu, 4 Sep 1997 23:56:54 -0400 (EDT)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
In-Reply-To: <199709042101.OAA20411@xxxxxxxx>

That was a pretty cool explanation, Bryan, and tied up some loose ends 
from the FAQ, for me. Bless you.




Michael Fetterman
d005041c@xxxxxxxx



On Thu, 4 Sep 1997 poqetpc-errors@xxxxxxxx wrote:

> 
> -------------- BEGIN poqetpc.v002.n009 --------------
> 
>     001 - Sabrodsky@xxxxxxxx         - Re: Digest poqetpc.v002.n007
>     002 - jdmorgan@xxxxxxxx (Justin - Looking for...
>     003 - sharriso <sharriso@xxxxxxxx - Re: Digest poqetpc.v002.n007
>     004 - Bryan Mason <bmason@xxxxxxxx - PCMCIA Discussion (was "Re: Digest poqetpc.v002.n006")
> 
> * This is a Poqet PC Mailing List digest.  Information on
> * replying to messages in this digest can be found at the
> * end of the digest.
> 
> 
> --------------- MESSAGE poqetpc.v002.n009.1 ---------------
> 
> From: Sabrodsky@xxxxxxxx
> Subject: Re: Digest poqetpc.v002.n007
> Date: Wed, 3 Sep 1997 16:34:01 -0400 (EDT)
> 
> Hi:
> When I had my Poqet I used to save files in text and then pop the card in my
> Omnibook 300 and read them with no problem.
> Regards
> By the way, anyone have a Poqet they are selling cheap?
> 
> 
> --------------- MESSAGE poqetpc.v002.n009.2 ---------------
> 
> From: jdmorgan@xxxxxxxx (Justin D Morgan)
> Subject: Looking for...
> Date: Wed, 3 Sep 1997 18:20:49 -0400
> 
> I'm looking for a used Poqet PC. Know where I can get one? It would be
> nice to have a new one, but I can't afford that.
> 
> That is, if I don't win one in an auction. I placed a bid on one for $45,
> and that includes shipping. It also has the serial cable, PC transfer
> software, and a memory card. Is that a good price or not?
> 
> Is there any place where you can still buy software for the 8088?
> ----------------------------------------
> Sent by Justin Morgan
> jdmorgan@xxxxxxxx
> Practice makes better.
> ----------------------------------------
> 
> 
> --------------- MESSAGE poqetpc.v002.n009.3 ---------------
> 
> From: sharriso <sharriso@xxxxxxxx>
> Subject: Re: Digest poqetpc.v002.n007
> Date: Wed, 03 Sep 1997 19:49:13 -0500
> MIME-Version: 1.0
> Content-Type: text/plain; charset=us-ascii
> Content-Transfer-Encoding: 7bit
> References: <199709030210.TAA09813@xxxxxxxx>
> 
> I have transferred files using both the serial null modem and via a
> pcmcia slot on a laptop I use at work.  The latter is vastly more
> convenient.  I understand it is advisable to format the memory card
> using the Poqet, or it may not be recognized by the Poqet if formatted
> elsewhere.
> 
> Steve Harrison
> 
> Ernest J. Yanarella wrote:
> > 
> >      Has anyone had experience using the PCMCIA slot on their laptop to
> > transfer and convert files to its floppy disk.  Mike Fetterman's recent
> > e-mail query elicited this question.  I find the present file transfer from
> > Poqet to Desktop PC so cumbersome and confusing that I have let me teenage
> > son do it.  Now that he started his first year of college, I am left high
> > and dry.  I like the Poqet for its convenience, small size, and
> > portability, but whenever I get a long file on it, I dread the prospects of
> > switching it to the desktop and to Word.  Help!
> 
> 
> --------------- MESSAGE poqetpc.v002.n009.4 ---------------
> 
> From: Bryan Mason <bmason@xxxxxxxx>
> Subject: PCMCIA Discussion (was "Re: Digest poqetpc.v002.n006")
> Date: Wed, 03 Sep 1997 23:38:31 -0700
> MIME-Version: 1.0
> Content-Type: text/plain; charset="us-ascii"
> 
> At 09:07 PM 8-30-97 -0400, Michael Fetterman wrote:
> 
> [...]
> 
> >Also, I know it is in the FAQ from Bryan, but could some knowledgeable 
> >person here initiate a discussion of the type and limitations of PCMCIA 
> >RAM cards (re: voltage, FRAM vs SRAM, linear, etc) as used in the Poqet ?
> 
> 
> Well, here's what I know about PCMCIA.  I hope it helps beyond what's in
> the FAQ.
> 
> Everyone please add what you know, clarify what might be a little
> confusing, correct me where I'm wrong, or pose questions to the rest of the
> group. 
> 
> SRAM CARDS
> ----------
> "SRAM" = "Static Random Access Memory"  SRAM is memory just like any other.
>  With static RAM, the memory does not have to be refreshed on a regular
> basis.  This is different than the kind of memory in your desktop computer,
> which is DRAM (Dynamic Random Access Memory).  In order for DRAM to hold
> its contents, it has to be actively refreshed from time to time.  Because
> SRAM doesn't require refreshing, it makes an ideal memory technology for
> portable PCMCIA cards -- you just have to provide a power source and the
> memory will keep its data as long as there is power.  SRAM is also good for
> PCMCIA cards because it is relatively low power and has very fast access
> times (relative to DRAM).
> 
> The bad thing about SRAM is that it is fairly expensive (relative to DRAM
> and Flash) and you can't pack as much capacity into a SRAM chip as you can
> with DRAM and Flash.  A single SRAM memory bit requires four transistors,
> whereas DRAM and Flash only require one transistor per bit (not including
> the addressing circuitry).
> 
> SRAM VOLTAGES
> -------------
> To read and write most SRAM, you need a 5 volt power supply.  If all you
> want to do is retain the data, but not access it, then all you need is 3
> volts.  All PCMCIA SRAM cards have a small 3 volt battery built in to them
> so that they will retain their data when they are not connected to a host
> computer.
> 
> The electronics inside the Poqet PC are designed to run at both 3 and 5
> volts.  The way the Poqet PC's circuitry works is that the system will run
> at 3 volts and a lower clock speed when it's not really doing anything, and
> then it will switch to 5 volts and a higher clock speed when it really
> needs to do some data crunching.
> 
> Before it tries to access an SRAM card, the Poqet PC switches to 5 volts,
> waits for the power supply to stabilize, and then begins reading from or
> writing data to the card.  The only problem is that, as the Poqet's AA
> batteries begin to die, it can't maintain that 5 volt level any more.  The
> system voltage begins to drop closer to 3 volts.  So with old batteries,
> the SRAM card is being accessed with a 3 volt power supply.  If the card
> isn't designed to support read/write accesses at 3 volts, then you'll get
> read errors or write errors -- data corruption and loss.  That's why the
> Poqet requires a "3 volt" SRAM card.  Unfortunately, the Poqet is nearly
> (if not completely) alone in this requirement, which is why it's so hard to
> find 3 volt SRAM cards.
> 
> FLASH Memory
> ------------
> Flash Memory (also called Flash RAM or Flash ROM) was invented by Intel.
> Flash Memory is a type of EEPROM (Electrically Erasable Programmable
> Read-Only Memory).  Flash Memory is like a ROM (Read-Only Memory) because a
> Flash Memory chip will store data even when power is removed from the chip.
>  But unlike ROM chips, you can also erase and reprogram the memory chip.  
> 
> Flash is much cheaper than SRAM (used to be about half the price, I don't
> know what it is today).  The limitation of flash is that you can't erase
> individual bytes -- you have to erase an entire block (like 512 bytes - 512
> KB).  So to change a single character in a file that's stored in a Flash
> Memory chip, you might have to erase and rewrite the whole file.  There are
> ways around this, however.
> 
> "Linear" Flash
> --------------
> The first kind of PCMCIA Flash cards were "Linear" Flash (I'm not 100% sure
> if that's what everybody called them, but that's the way we referred to
> them at Poqet).  Linear Flash cards were just a bunch of Flash Memory
> inside a flash card.  To put files on the card, you had to program the card
> all at once.  We used to use an old Databook PCMCIA card reader/programmer
> and a program that Databook wrote called "TCXCOPY" to program the cards.
> TCXCOPY did some magic where you could always add new files to a card, but
> if you wanted to remove files, you had to erase the whole card and start
> over.  
> 
> That's the way it worked on the Poqet.  You used TCXCOPY to add files to
> the card, and when it got full, you used TCERASE to erase the card and
> start over.  Not a great solution, but it worked pretty well when you could
> get 4 MB of Flash storage for the price of 2 MB of SRAM storage.
> 
> The other way you could use Linear Flash was to use a "Flash File System"
> (FFS).  The Flash File System drivers would run in DOS and would
> automatically manage the Flash card for you.  So if you wanted to replace a
> file, the Flash File System would automatically erase and rewrite the file
> for you.  With FFS, you didn't have to worry about the TCXCOPY/TCERASE
> thing.  
> 
> Alas, we never got a Flash File System working on the Poqet.  Actually, FFS
> didn't seem to be around very long because something much better came along
> -- SunDisk cards.
> 
> SunDisk
> -------
> SunDisk had a really cool idea.  They decided that the Flash memory
> technology was great, but that the hassle of managing the memory with
> TCXCOPY/TCERASE and/or FFS was a major pain.  So what they did was to take
> a bunch of Flash Memory and put it in a card with a microcontroller that
> had the task of managing the memory.  On the other side of the
> microcontroller was the newly standardized PCMCIA/ATA interface.
> PCMCIA/ATA is a standard that makes it so a PCMCIA card looks alot like the
> standard ATA disk interface that's in most PCs.
> 
> Anyway, the block diagram of a SunDisk card kindof looks like:
> 
> HOST COMPUTER <==============> MCU <====> FLASH MEMORY
>                (PCMCIA/ATA)
> 
> A SunDisk card is, in concept at least, identical to a hard disk drive.
> The host computer talks to a microcontroller which is responsible for
> managing a bunch of memory.  In a disk drive, the "bunch of memory" is
> located on rotating platters.  In a SunDisk card, the "bunch of memory" is
> actually a couple megabytes of Flash Memory.  The host computer just says
> "write this data to location such-and-such" and the microcontroller is
> responsible for doing all of the "program/erase/reprogram" stuff that we
> used to do with TCXCOPY/TCERASE.
> 
> Pretty cool (at least I think so).
> 
> Several years ago, SunDisk changed their name to "SanDisk."  The rumor was
> that Sun Microsystems felt that SunDisk was infringing on their copyrights.
>  I don't know if that's true, but that was the rumor.
> 
> The only problems with SunDisk cards are:
> 1) The amount of time required to write data is pretty slow.  Faster than a 
>    hard drive, but slower than an SRAM card.  This because of the whole 
>    program/erase/reprogram cycle that needs to be done -- the erase/reprogram 
>    cycle takes a relatively long period of time.
> 2) They don't work on Poqet PCs.
>    (Well, some actually work on Poqet PC Plus's -- but not on Poqet PC 
>    Classic's or Prime's.)
> 
> 
> ______________________________________________________________________
> Bryan Mason, Menlo Park, California, USA, Earth
> e-mail:                <bmason@xxxxxxxx>
> Poqet PC Home Page:    <http://www.best.com/~bmason/PoqetPC/>
> Poqet PC Mailing List: <PoqetPC@xxxxxxxx>
> 
> 
> --------------- END poqetpc.v002.n009 ---------------
> 
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Re: Digest poqetpc.v002.n009 by Michael Fetterman <d005041c@xxxxxxxx>


From: Michael Fetterman <d005041c@xxxxxxxx>
Subject: Re: Digest poqetpc.v002.n009
Date: Fri, 5 Sep 1997 00:01:05 -0400 (EDT)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
In-Reply-To: <199709042101.OAA20411@xxxxxxxx>

So besides the rare 3 volt SRAMs (what brands besides original POQET may 
be 3 volt ?), what brands of Flash RAM (FRAM ?) cards can we Classic users 
use with impunity ? FRAMs sound like a superior way to go to me. If 
SANDISK/SUNDISK pieces are a no-no, are most linear FRAMs cool ? Brands ?
Is the eraser/program software still available ? Is it included with a 
POQET programmer (and maybe now I can see why I want one) ?


Michael Fetterman
d005041c@xxxxxxxx






Filename: PoqetPC/mailing-list/cgi/show-digest.htmt
Date Created: 30 Nov 1996, Last Modified: 13 May 2009
Created by Bryan Mason - E-Mail: poqetpc<at>bmason<dot>com