dillon@CORY.BERKELEY.EDU (Matt Dillon) (07/24/88)
Well, I have successfully connected my microbotics SCSI controller to an Adaptec ACB4000A, which is in turn connected to two seagate 4096's (You might wonder how I could get along without HDs until now). Yes, that's 80x2 = 160MB. For those who have the microbotics controller and are thinking along the same lines, it doesn't work out of the box... you have to use their undocumented send-SCSI-command in the StarDrive.device to send some configuration info to the Adaptec before it will accept a format command. I wrote some code to do it... feel free to email me if you want it. My exact configuration is: -Microbotics StarBoard II w/ SCSI controller, realtime clock, 2MB -Home Made 25pin->50pin SCSI cable -Mail Order duel full-height disk drive enclosure w/ power supply -Adaptec 4000A (mounted inside and powerd by the enclosure) -Cables for connecting the Adaptec to the drives -Two Seagate 4096's, placed in and powerd by the enclosure. Fortunetly, Adaptec has *very* good technical manuals, Kudos. Once I had figured that out I was able to low-level format the two drives, set up my MountList for four 40MB partitions, and then format them. It works great! BUT There appears to be a problem when you tell it to seek long distances (inherent seek in the read and write's). The Adaptec 'freezes' for up to 3 seconds when I want to seek more than a dozen cyls. This results in fine operation in a given partision, but accessing between two partitions on the same drive cause incredible delays. I.E. (1) send command that causes long seek, (2) Adaptec freezes for up to three seconds WITHOUT seeking the drive, (3) the drive seeks to the proper place quickly (tens of ms, like it should). (Actually, this delay appears to be proportional to the # of cyls, the more cyls, the longer the delay) Does anybody know if this is a problem with the microbotics driver? or the Adaptec? or what! Thanks! -Matt P.S. Oh yah. I don't really like the microbotics driver... it freezes the computer up for short (or long) periods of time when accessing the disk. To put it mildly, there are absolutely no timing constraints on the SCSI controller they are using (non DMA) to warrent this.