skl@van-bc.UUCP (Samuel Lam) (09/24/89)
In article <17680@bellcore.bellcore.com>, karn@jupiter.bellcore.com (Phil R. Karn) wrote: >I recommend that you try replacing the 8250 or 16450 chips with National >NS16550 chips, which have 16-level FIFOs built into the receiver and >transmitter. > >These chips function just like 8250s unless they are explicitly put into >FIFO mode by software. Do you mean I can physically replace the 8250 on my serial board with a 16550? Wouldn't there be some trouble with the difference between edge and level triggered interrupts? Has anyone actually tried this, and how did the 16550 perform compared to the 8250? I am interested in this because we use KA9Q as an SLIP-Ethernet IP router here and it runs wonderfully at 2400 but not at all at 9600, and we would like to run it at the higher speed. Thank you very much for your time. ...Sam -- Samuel Lam <skl@wimsey.bc.ca> or {uunet,ubc-cs}!wimsey.bc.ca!skl
karn@ka9q.bellcore.com (Phil Karn) (09/24/89)
In article <302@van-bc.UUCP> skl@wimsey.bc.ca (Samuel Lam) writes: >Do you mean I can physically replace the 8250 on my serial board with >a 16550? Wouldn't there be some trouble with the difference between >edge and level triggered interrupts? Yes, I've done this in my two PCs (one AT and one XT). They work just fine with amateur packet radio TNCs, but I haven't actually tried it yet in gateway mode with real SLIP. I set up the receive FIFO in the 16550 to interrupt at the 1/4 full point, so at 9600 bps the code has an extra 12 ms to respond to the interrupt. This is a big improvement. Phil
larry@nstar.UUCP (Larry Snyder) (09/27/89)
> Do you mean I can physically replace the 8250 on my serial board with > a 16550? Wouldn't there be some trouble with the difference between > edge and level triggered interrupts? The 16550A is a direct replacement for the 8250 and 16450. > Has anyone actually tried this, and how did the 16550 perform compared > to the 8250? The 16550A chips are worth the cost of the chip in high speed applications (greater than 9600 baud). My machines' throughput on the serial lines increased by 40% after replacing the 16450 chips with 16550A's. -- Larry Snyder uucp:iuvax!ndcheg!ndmath!nstar!larry The Northern Star Usenet Distribution Site Notre Dame, IN USA