Hi,
> On Wed, 26 Jul 2000, Ron Farrer wrote: > > > What would work better in an Alpha; an Adaptacrap 1542C or 1520B? > > Don't think either work. I tried an Adaptec 1542C in the past and it > never worked due to horrid dma/memory mapping and, from what I understand, > it's not fixable. The problem is, that DMA transfers can't go beyond 16Mb on ISA native. However, I have seen drivers using bounce-buffers below 16mb, moving data to/from the target memory-space. A ( guick ) glance through Linux' scsi drivers revealed, that the ISA Buslogic cards seem to make use of this method. However, looking at the aha1542.[hc] revealed no clear picture ( to me ). It seems, that *any* transfer beyond 16Mb results is a panic() call. ( see macro BAD_DMA in aha1542.c ). Actually, I found it hard to believe, that this is actually the case. This problem has been fixed in numerous x86 *NIX implementations ( at least Solaris and SCo did, to my knowledge ). Also, I assumed, that modern PCI-ISA bridges woudl fix this problem "automagically". However looking at the generic isa-dma code for Alphas, there appears to be a limit at 48Mb. > I haven't tried the 1520B, but I'm assuming it's more of the same. In my > experience, it's much better to get a PCI SCSI adapter (I've got a Tekram > 390F...only like $70). The 1520 uses polled I/O, not DMA. I've never seen one - it was said to be an awful slow dog at the time it was introduced. But I assume, it *could* work. Also, if you ( Ron Farrer ) has the option of choosing, I would probably go for a BusLogic. At least the driver uses bounce-buffers. Anyway, it's very late now ( in Germany ) and i'll finish now. Just my $.02 Sincerely Thomas Weyergraf > -- > To UNSUBSCRIBE, email to [EMAIL PROTECTED] > with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED] > -- Thomas Weyergraf [EMAIL PROTECTED] My Favorite IA64 Opcode-guess ( see arch/ia64/lib/memset.S ) "br.ret.spnt.few" - got back from getting beer, did not spend a lot.
