In <Bxn4nM.Msu@fc.hp.com> chuckc@fc.hp.com (Chuck Cairns) writes:
>: >To make a long story short "if you get a caching
>: > disk controller YOU LOSE THE OPTION of where the memory gets used."
>:
>: I disagree. I have a IDE cache-ing controller on my new PC (486DX-33). At first I was dubious of the benefits of a hardware cache over the software option, but not now.....
>: The main advantage is that your main CPU is not burdened with the mundane cache control functions and can get on with pushing Windows (or whatever) along.
>: It is particularly noticeable to me when I'm compiling, I save then compile my source code, with the IDE cache this is done in parallel, software cacheing could not do this.
>: A further advantage is gained if you use "write-back cacheing" (disk writes are cached as well as reads). If you use software chaching and your machine crashes (not so unusual even under Win 3.1) bang goes your new data... This does not happen in hardware chaching.
>
>This is not necessarily true! Certainly there are cases where a software crash
>can occur and the hardware controller will save you. BUT a power glitch, for
>example (unless you have a an UPS) could just as easily lose date on the card
>as in main memory. Non-volatile hardware cache would be super.
>Don't confuse adding more CPU power ( i.e. the CPU on the controller)
>with a direct hardware cacheing "advantage". If you spend X dollars
>more for a cacheing controller, what extra CPU power could you have
>gotten instead. Buying the faster CPU instead gets you the power to use in a
>broad range of areas not just to move bytes onto the disk. This is also
>why I am a fan of SCSI with bus-mastering. Here the CPU doesn't ((may
>not )have to move the bytes at all since the SCSI card does all the
>work. Moreover, one can have several seeks/writes/reads all in process
>at once.
EXACTLY what I meant by suggesting he get an intelligent controller.
I'm using a 32-bit SCSI bus-master. Just tell it to get the stuff off
disk and put it somewhere, then the CPU can go on and not have to
worry about it because the drive takes care of all the details.
>In short, probably the most effective is to add memory and CPU speed
>with straight IDE and then go SCSI if you need more performance.
Yeah, it's really kind of funny that people are concerned about all
these speed issues and then they go to using IDE and Local Bus stuff
that requires constant direct CPU attention. If you want speed,
BALANCE THE SYSTEM. Offload all that I/O processing to an intelligent
controller like a SCSI and to a processed video board (instead of a
dumb frame buffer hanging right off the CPU bus).
--
"Insisting on perfect safety is for people who don't have the balls to live
in the real world." -- Mary Shafer, NASA Ames Dryden
