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- Path: sparky!uunet!ogicse!reed!news
- From: rseymour@reed.edu (Robert Seymour)
- Newsgroups: comp.sys.ibm.pc.hardware
- Subject: Re: Ram Disk Drive (solid state)
- Message-ID: <1992Nov11.063558.29519@reed.edu>
- Date: 11 Nov 92 06:35:58 GMT
- Article-I.D.: reed.1992Nov11.063558.29519
- References: <1992Nov10.195126.8596@iscsvax.uni.edu>
- Sender: news@reed.edu (USENET News System)
- Reply-To: rseymour@reed.edu
- Organization: Reed College, Portland, OR
- Lines: 61
-
- In article <1992Nov10.195126.8596@iscsvax.uni.edu> simmons5275@iscsvax.uni.edu
- writes:
- > Hi, I was recently looking through some back issues of radio electronics and
- > found an interesting piece about a dsolid state disk drive made from static
- > ram. I would be very interested in thins product except that it has capacity
- to
- > store only 512k of info. Today 512k is nothing. I was wondering whether
- anyone
- > has heard of a larger version, perhaps up to 64 meg :) That would interest me
- > very much. The solid state drive must have ability to hold info when the
- system
- > is turned off though or it wouldnt be of much interest to me. Imagine the
- > access time on solid state static ram drive =). If anyone has info on either
- > the existence or lack there of, id appreciate if they would send me the info
- > withthe manufacturers name .. etc thanks.
- >
- >
- > Robert
- >
- > ======================================================================
- > | Snail Mail Address : | I just follow instructions. |
- > | Robert E. Simmons Jr. | After all my inteligence is only |
- > | 347 Shull Hall | artificial. :) |
- > | University of Northern Iowa | |
- > | Cedar Falls, IA 50614 | -> "Dare to know." from 'What is |
- > | Email Address: | -> Enlightenment' by Imannuel |
- > | Look at the mail header! | -> Kant. ca. 1850 |
- > ======================================================================
-
- Solid state RAM drives are usually made of banks of DRAM (dynamic
- random access memory) and placed on a single card which is put into the local
- bus. Most often the card itself is just a bunch of SIMM slots and a few pieces
- of additional curcuitry. An SRAM card would have to be on the system bus to be
- useful (i.e. to make use of the additional speed of SRAM [SRAM c. 10-30ns, DRAM
- c.70-120ns].
- Most RAM drives are used for graphics manipulation where reading from
- disk at high speed is critical. They are very expensive (per megabyte compared
- to disk drives), and the new DRAM tariff won't help. I wouldn't suggest a drive
- unless you use high speed graphics programs and have an EISA bus. A better
- solution is a SCSI-2 fast and wide card with a RAID level 0 disk array (i.e.
- data-stripping, although level 3 or 5 may be fast enough with the new 3.5"
- large capacity drives).
- Another type of RAM drives are virtual RAM drives. These are crated by
- a partition in the main system memory. They have the advantage of being
- transferrable to main memory, and the software is cheap. Both of these types of
- RAM drives do not have backup power, so any information is lost on power-down.
- There are also some solid state external RAM drives which have an internal UPS,
- but they are extremely expensive and I couldn't imagine an application where
- they would be useful to a PC (the're mostly for supercomputers or very fast
- servers and workstations).
- Another example of RAM drives are the memory cards used in some
- handhelds or pen computers (also in calculators). They use a bank of SRAM with
- a battery (lithium) backup. However, they aren't feasable in high capacity at
- the moment. I gather that a RAM drive is not really what you need, a fast disk
- could do everything you need and be as fast as the PC can handle.
-
- --
- Robert Seymour rseymour@reed.edu
- Departments of Physics and Philosophy
- Artificial Life Project Reed College
- Reed Solar Energy Project (SolTrain) Portland, OR
-