howard@amdahl.UUCP (02/27/87)
In article <6341@mhuxu.UUCP> davec@mhuxu.UUCP (Dave Caswell, sorta) writes: > .....From an engineering >standpoint, SuperMac's souped-up SCSI manager is *worse* than the original: >it has more timing dependencies and works correctly with fewer SCSI devices. > . > . > ....If you >move too fast, you suffer over-run while writing or under-run while >reading, and the Mac dies a confusing death. SuperMac's big speed-up >comes from tweaking their data transfers so that they're precisely tuned >to their disks. It's risky as hell, but they don't tell their customers >that. Apple's blind transfers are deliberately slower so that they'll work >with a larger variety of devices. > Ok. It all makes sense. But, how come my Mac hasn't died a confusing death? I've run both a DF20 at various initializer levels as well as my current DF20XP. Here's the rub; I have a Monster Mac board giving the Mac an extra performance kick. If the timing was so tight, how come the whole thing hums along without so much as a glitch. Did Ephriam actually disassemble the Supermac driver to figure all this out? Will newer Macs have sensible hardware? Will they have a sensible price? Will the Natl. Enq. cover the new annoucements? I have an enquiring mind. I wanna know! -- "Plan for the future because that's where you Howard C. Simonson are going to spend the rest of your life." {hplabs,ihnp4,nsc}!amdahl!howard - Mark Twain - [ The disclaimer for this message may be found in my next article ]
dwb@well.UUCP (02/27/87)
The reason the DataFrame XP20 works fine on your MonsterMac even though it is timing dependent and the Monster gives you a performance improvement is that the DataFrame XP driver jumps into the ROM. This solves two things. First, the timing is consistent between the two because the Monster only executes out of some ram faster, the ROM code runs the same. Second you don't have to worry about your dataframe still running under newer roms or machines. It flat won't... By the way, another vendor that do the same thing (jump into the rom) and therefore perhaps ought to be seriously thought about is MDIdeas with their TDBK tape drives. David -- David W. Berry dwb@well.uucp dwb@Delphi dwb@GEnie 293-0752@408.MaBell
naftoli@aecom.UUCP (03/01/87)
In article <2666@well.UUCP>, dwb@well.UUCP (David W. Berry) writes: > Second you don't have to worry about your dataframe still running > under newer roms or machines. It flat won't... By the way, another > vendor that do the same thing (jump into the rom) and therefore perhaps > ought to be seriously thought about is MDIdeas with their TDBK tape > drives. Although you are probably correct in saying that it might not run with newer machines, this is perhaps not as big a deal as one would think. Given that a new machine comes out and won't run with the XP series, how long do you think it would take Supermac to come out with an upgrade to make it work? They'd be stupid not to put it on the top priority list. -- Robert N. Berlinger Systems Analyst, Scientific Computing Center Compuserve: 73047,741 Albert Einstein College of Medicine Easylink: 62956067 UUCP: ...{philabs,cucard,pegasus,rocky2}!aecom!naftoli GEnie: R.Berlinger