🚀 go-pugleaf

Ivo Clarysse (soggie@starlab.net) wrote:

: - Active ISDN ISA/PCI cards has the least computer impact.
: - External ISDN TAs don't eat up a lot of CPU-cycles, but
:   every byte on the serial port triggers an interrupt.

Modern UARTS have fifo's for xmit en receive. A 16550 for example has 16bytes 
fifo, so you won't get an interrupt for each byte. There are more advanced
UARTS which have a greater buffer size. There also exist serial cards with 
DMA (eg: Hayes ESP which is supported by 2.1.x).

: - Passive ISDN TAs have the most impact.

Depends on which mode you use them in. The HSCX has about 32bytes fifo if I 
remember correctly. So if you use HDLC or syncPPP, you will get less interrupts
then if you would use an external TA with a 16550 UART. So system load will
probably be slighty lower. There is also a very small amount of traffic on the
D channel to keep the EDSS1 connection alive, but this is neglible compared
to HDLC traffic during internet use. Things change when you would use V110
(which isn't implemented in Hisax afaik, so you would have to write it first :))
as the ISAC doesn't have a FIFO, you would get an interrupt for each byte.

: > I just whant to use the ISDN for surfing. (if possible also at
: > 128 Kbit/s).
:  

Ok. In that case, multilinkPPP should fit the bill. This works very nicely
on a teles card.

: > The box is a 120 Mhz. pentium (copmpaq prolinea 5120), with 32 Mbyte
: > of RAM and a '16550A' serial-port?

: I think the 16550A is limited to 115200 Kbps.

The 16550AFN variant can go higher, but the normal UART clock limits it to 
115200Bps. There exist serial cards with a higher UART clock, which allow
you to go up to about 400Kbps.

: I've used Teles 16.3 passive ISDN cards in a Pentium-120 with 8MB RAM
: (a long time ago) without problems.


We are using a Teles 16.3 passic ISDN card as well in a cyrix 486/66 machine
without problems.

In general I would recommend using a teles board, unless you need some features
it does not provide like a/b adapter or normal V series modem protocol support.
In that case you might be better looking at an external TA. 

Peter.