On Fri, Apr 09, 2004 at 02:01:56PM -0400, Louis A. Mamakos wrote: > > Those cards are just what they are - cheap. > > They have very small FIFOs and they don't use DMA. > > IRQ sharing makes them even worse than traditional ISA stuff. > > My advise for cost efficient and fast serials is getting USB ones. > > Even noname USB serials do much better then puc(4) based. > > E.g. the FT232BM (uftdi(4)) has 128 bytes send and 384 bytes receive > > buffer plus your USB controller does DMA. > > At best you would add a cheap OHCI card if your onboard USB is UHCI > > based as OHCI is less CPU intensive. > > I used to use 9600 bps serial links on LSI-11/23 systems 20 years ago > to run SLIP over. This was with dumb DL-11 serial adapters on way > slower CPUs and busses than we have today. The difference was a > much lower interrupt latency. You'd think that running serial links > 10 times faster on CPUs that are a few hundred times faster wouldn't > be too hard.
I'm not saying that interrupt latency is OK and that it's impossible to get things running with this kind of hardware, but it's very questionable that you have a fast CPU with fast IO bandwidth just to waste cycles for cheap hardware while you can easily get much more efficient hardware for your money. 16550 design is ancient - having them addressed via PCI doesn't change very much. You are also not running your Fastethernet with the same mechanisms as you did with your 10 times slower ISA NIC. -- B.Walter BWCT http://www.bwct.de [EMAIL PROTECTED] [EMAIL PROTECTED] _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
