Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!lsuc!jimomura From: jimomura@lsuc.UUCP Newsgroups: comp.sys.m6809 Subject: Re: 512K RAM upgrades Message-ID: <1997@lsuc.UUCP> Date: Mon, 17-Aug-87 23:37:17 EDT Article-I.D.: lsuc.1997 Posted: Mon Aug 17 23:37:17 1987 Date-Received: Wed, 19-Aug-87 01:39:33 EDT References: <5013@milano.UUCP> Reply-To: jimomura@lsuc.UUCP (Jim Omura) Organization: Consultant, Toronto Lines: 36 Keywords: OS9 CACHE SDOS Summary: Caches and stuff In article <1607@tekgen.TEK.COM> jonh@tekgen.UUCP (Jon Howell) writes: >+>You're right, Pete--we'd LOVE that cache! Also, that nice effect of open key- >+>board during disk access. Also, does that mean the chars show on the screen, >+>or are just read? >*Keyboard 'lockout' is ususally caused by the way the floppy controller >*is set up and used. As delivered, the standard RS controller (and most >*of the clones) are programmed to actually HALT the 6809 during data >*xfer.. the only thing that gets the 6809 out of the loop is a NMI >*(non-maskable interrupt), if I recall correctly. >So, what does this mean? Can Level II read keyboard ahead well? Can the ACIA >also be read ahead? (I will write a BBS when I get my copy of LII) Well, I have to disagree with the trend here. I don't like full cache for OS-9 systems. There are a *lot* of different approaches to speed and system integrity. Full read/write cache adds speed but at substantial risk of data loss and file corruption in the case of power failure or other hardware flakey failure. Thanks guys, but no thanks. Data integrity is too important for me to risk that. Read cache--which was done by TLM on the Atari ST OS-9 port was, in my opinion, the best compromise. Keep in mind that OS-9 allows you to *preload* object files. This is much more efficient than cache. Secondly, for datafiles, it's faster to throw intermediate files and reasonably small files into a RAM disk. If a file won't fit in, say a 512K RAM disk, a cache isn't likely to help that much either. A RAM disk has most of the same problems for data integrity as a cache, but at least you have an inherently better chance of retaining the "old copy" intact even if you lose the copy in RAM disk. A partially updated disk copy when the power goes down (or other "bad crash") is generally worthless. Cheers! -- Jim O. -- Jim Omura, 2A King George's Drive, Toronto, (416) 652-3880 ihnp4!utzoo!lsuc!jimomura Byte Information eXchange: jimomura