cotner@BRAHMS.BERKELEY.EDU (Carl Cotner) (12/22/88)
I have an AT clone that runs at 12MHz; unfortunately, I think the bus speed also runs at that rate. I've tried to install a Western Digital hard disk controller WD-1003-WA2 on my motherboard, but I'd get write errors on my hard disk which end up corrupting the file I was trying to access. I also have an NCL controller which runs fine at 12MHz, however this controller doesn't seem to run Xenix. I can never get pass the Xenix installation; as soon as it tries to scan the hard disk (an ST 251-1) for bad sectors, Xenix belches "PANIC TRAP", displays the contents of the 80286 registers, and then dies. This is getting mighty aggravating. Can someone please recommend to me a disk controller card that will operate at 12MHz, and will run Xenix? Carl cotner@brahms.Berkeley.EDU
dave@micropen (David F. Carlson) (12/22/88)
In article <8812220135.AA04469@brahms.berkeley.edu>, cotner@BRAHMS.BERKELEY.EDU (Carl Cotner) writes: > > I have an AT clone that runs at 12MHz; unfortunately, I think the bus > speed also runs at that rate. I've tried to install a Western Digital > hard disk controller WD-1003-WA2 on my motherboard, but I'd get write errors > on my hard disk which end up corrupting the file I was trying to access. >I also have an NCL controller which runs fine at 12MHz, however this controller > Carl > cotner@brahms.Berkeley.EDU I have had a prominent clone maker give a fairly reasonable explanation for the failure of certain disk controllers at high speed EVEN if the bus is run at 8MHz compatibility mode. Particular among the failures is the most common of all AT boards: WD1003-WA2! It seems the bus precharge cycle is a function of bus length (reasonable given capacitance over the bus, etc.) When the bus is speed up, the precharge cycle must remain relatively fixed (as capacitance would also remain fixed) however, certain boards (WD1003 among them) calculate the precharge timing themselves and access the bus at inappropriate times. Ouch. We thought it was us for a long time and I got quite far into tech support before this little gem leaked out. (And yes, UNIX installs gave the most troublesome operation.) This manufacturer claims that *EVERY* high speed AT bus computer will have the problem because it is one of physics and incomplete specs. That includes 12/16MHz 286, all 386 and even 386SX. Certain cards that were made for high speed operation do work: the new WD1006-V is a good bet if you can get one! (1:1 interleave controllers are almost all better than 3:1 for high speed buses. This is a gross generalization but essentially correct.) -- David F. Carlson, Micropen, Inc. micropen!dave@ee.rochester.edu "The faster I go, the behinder I get." --Lewis Carroll