ted@blia.BLI.COM (Ted Marshall) (11/13/86)
There is a ram disk driver on the VMS 4.2 and later distribution. It is called PDDRIVER. DEC uses it in SYS$UPDATE:STABACKIT.COM when building stand-alone backup kits for micro-VAX media. However, DEC didn't want users to be able to use it so instead of including the required initialization code in a separate file, the MACRO code is in-line in the .COM file. It assembles it, uses it and then deletes it. There was also an article on PDDRIVER in either DEC PROFESSIONAL or VAX PROFESSIONAL magazine within the last two months. Check out the files and/or the magazine. I haven't actually tried to use the driver but I know that it is used by the command file. Also, I don't have any performance figures. The story I heard at fall DECUS was that someone asked a developer what PDDRIVER is. The developer responded "That's not supposed to be on the tape!" Hope this helps. Ted Marshall @ Britton Lee, Inc. (408) 378-7000 [ I would put my network address here, but I'm a new net user and I haven't figured out what it is yet! ]
sasaki@endor.harvard.edu (Marty Sasaki) (11/18/86)
There is a problem with PDDRIVER, the inner loop (moving bytes from the "disk" to the user's address space) uses MOVB, which on a uVAX II is increadibly slow. We haven't tried it on other processors. Just a warning. ---------------- Marty Sasaki uucp: harvard!sasaki Strategic Information arpa: sasaki@harvard.harvard.edu 80 Blanchard Road bitnet: sasaki@harvunxh Burlington, MA 01803 phone: 617-273-5500