mead@uxh.cso.uiuc.edu (06/05/90)
This is a hardware query, bail out now if you're not interested. Sorry if this is vague, but at least I'm accurately communicating the contents of my working memory:( Anyway, my advisor mentioned seeing an ad (in, say, PC Magazine) for a piece of hardware (a card?) that boosted your effective disk space by 200% (or something). I could (probably will) hunt down the product name etc, but I was hoping someone out there can discuss the field in general or even offer experiences. Any advice would be appreciated (by email even more!), but the kind of things we're wondering are stuff like: Would it be as effective as PD software such as PKZIP? It would (de)compress "on the fly" (right?), so how would disk access time be effected? (Or, how bad is the damage?) How reliable is the technology (what happens if the power goes in the middle of compression?) ... Again, any help would be appreciated and thanks in advance. -alan mead : mead@uxh.cso.uiuc.edu
koziol@yoyodyne.ncsa.uiuc.edu (06/06/90)
I saw this article in this months issue of Byte (p.44): DOUBLE YOUR DATA STORAGE CAPACITY WITH $199 CARD The InfoChip Expanz! is a compression coprocessor card with a proprietary chip that compresses data on random-access data storage devices, such as floppy and hard disk drives. Expanz! offers transparent compression and decompression and does not slow down your access to the stored data, the manufacturer says. The method of compression is "lossless" as compared to video compression, where a certain amount of data can be lost but is not noticeable when you look at the compressed and decompressed video. The 8-bit half-length Expanz! will work with any DOS 3.x application and averages a 2.5-to-1 compression ratio. That means that your 20-MB hard drive will hold about 50 MB of data, and your 100-MB SCSI drive will hold 250 MB. The overhead for compression on a hard disk averages 3 percent of the size of the original hard drive, or less than 1 MB in the case of a 20-MB drive. Once you have Expanz! installed on your XT or AT and you are ready to compress the files on your 20-MB hard disk drive, the compression process takes about ten minutes. Thereafter, Expanz! will compress and decompress files as you use your computer. And because you are them reading compressed files (e.g., three sectors of the disk now map to one), the read time is somewhat faster than it was with uncompressed files. The time will not be substantially less for hard disk drive reads, but floppy disk drive reads are said to be about three times faster. PRICE: $199 CONTACT: InfoChip Systems, Inc. 2840 San Thomas Expy. Santa Clara, Cal. 95051 (408) 727-0514 ============================================================================= I haven't called them yet, but some of the information I would like to know would be: What about DOS's 32MB drive partition, how does their card deal with large drives, etc..? What about caching disk controller cards, how are they dealt with? Is their some way to uncompress your data again (say to distribute a floppy to someone without this card)? If they can deal with these potential problems realistically, I may pick the card up. Quincey Koziol Programmer NCSA koziol@ncsa.uiuc.edu