What are drawbacks to using an ISA NIC?

What are drawbacks to using an ISA NIC?

Post by Steve Snyde » Mon, 31 May 1999 04:00:00



I discovered (by trying to use it) that the last unused PCI slot in my
system is defective.  This forced me to add an ISA NIC (a 3Com 3C509B)
instead of the PCI device I had planned on.

The ISA NIC is working well.  I wonder, though, what the drawbacks are
compared to a PCI NIC.  This device is just attached to a cable modem,
which suggests that it will never be called upon to move more than
3MB/second anyway.

Is interrupt latency higher with an ISA NIC?  Increased CPU use?  The
initial install involves more work because you have to specify the IRQ and
I/O port address range.  Now that the installation is done, though, I'm
interested in runtime gotchas.

Thank you.

***** Steve Snyder *****

 
 
 

What are drawbacks to using an ISA NIC?

Post by Frank Sweetse » Mon, 31 May 1999 04:00:00



> I discovered (by trying to use it) that the last unused PCI slot in my
> system is defective.  This forced me to add an ISA NIC (a 3Com 3C509B)
> instead of the PCI device I had planned on.

> The ISA NIC is working well.  I wonder, though, what the drawbacks are
> compared to a PCI NIC.  This device is just attached to a cable modem,
> which suggests that it will never be called upon to move more than
> 3MB/second anyway.

> Is interrupt latency higher with an ISA NIC?  Increased CPU use?  The
> initial install involves more work because you have to specify the IRQ and
> I/O port address range.  Now that the installation is done, though, I'm
> interested in runtime gotchas.

the biggest gain is it's a 32bit bus, vs the 16bit ISA bus.  it's also a
nice feature that the PCI bios managed resources (I/O ranges, IRQs) and
provides a nice, easy, safe way to get at 'em.  i *think* the PCI bios can
also help move data around w/less work from the host CPU, at least on
bus-mastering cards, but if it's just hooked up to a cable modem you'll
probably never even max out the ISA bandwidth.

--
Frank Sweetser rasmusin at wpi.edu fsweetser at blee.net  | PGP key available
paramount.ind.wpi.edu RedHat 5.2 kernel 2.2.5        i586 | at public servers
`When you say "I wrote a program that crashed Windows", people just stare at
you blankly and say "Hey, I got those with the system, *for free*".'
(By Linus Torvalds)

 
 
 

What are drawbacks to using an ISA NIC?

Post by Tim Moor » Mon, 31 May 1999 04:00:00


ISA is clocked at 8.3MHz, PCI at 33MHz.  ISA has more CPU overhead too.

This card is 10bT if I recall correctly, so it won't move more than
about 850KB/s.  If you want 3MB/s you'll have to go 100bT which means
PCI.

Are you sure the slot is defective?  My PCI slots 4&5 share an IRQ which
could cause weird behavior under some circumstances.  Other boards that
have built-in SCSI, sound, etc are known to share IRQ's with particular
PCI slots.


> I discovered (by trying to use it) that the last unused PCI slot in my
> system is defective.  This forced me to add an ISA NIC (a 3Com 3C509B)
> instead of the PCI device I had planned on.

> The ISA NIC is working well.  I wonder, though, what the drawbacks are
> compared to a PCI NIC.  This device is just attached to a cable modem,
> which suggests that it will never be called upon to move more than
> 3MB/second anyway.

> Is interrupt latency higher with an ISA NIC?  Increased CPU use?  The
> initial install involves more work because you have to specify the IRQ and
> I/O port address range.  Now that the installation is done, though, I'm
> interested in runtime gotchas.

> Thank you.

> ***** Steve Snyder *****

--
direct replies substitute timothymoore for user name

"Everything is permitted.  Nothing is forbidden."
                                   WS Burroughs.

 
 
 

What are drawbacks to using an ISA NIC?

Post by Frank Sweetse » Tue, 01 Jun 1999 04:00:00



> ISA is clocked at 8.3MHz, PCI at 33MHz.  ISA has more CPU overhead too.

yep, i'd forgotten about the vast difference in speed.

Quote:> This card is 10bT if I recall correctly, so it won't move more than
> about 850KB/s.  If you want 3MB/s you'll have to go 100bT which means
> PCI.

knowing the cable modem speeds i've seen, he probably meant 3Mbits, not
3Mbytes.

Quote:> Are you sure the slot is defective?  My PCI slots 4&5 share an IRQ which
> could cause weird behavior under some circumstances.  Other boards that
> have built-in SCSI, sound, etc are known to share IRQ's with particular
> PCI slots.

other random thought - perhaps you're trying to put a bus mastering card
into a non-busmastering slot?  try swapping cards around, it may
mysteriously start working again.

--
Frank Sweetser rasmusin at wpi.edu fsweetser at blee.net  | PGP key available
paramount.ind.wpi.edu RedHat 5.2 kernel 2.2.5        i586 | at public servers
If this were Ada, I suppose we'd just constant fold 1/0 into

    die "Illegal division by zero"

 
 
 

What are drawbacks to using an ISA NIC?

Post by Tony Plat » Tue, 01 Jun 1999 04:00:00



>ISA is clocked at 8.3MHz, PCI at 33MHz.  ISA has more CPU overhead too.

Yes and ISA does 16MB/sec (thats 16 megabytes per second) 10 base T is 10
Mega BITS a second>>>>>big difference. So ISA should more than well cover
the requirements

Quote:>This card is 10bT if I recall correctly, so it won't move more than
>about 850KB/s.  If you want 3MB/s you'll have to go 100bT which means
>PCI.

There are ISA and EISA 100bT cards around

>Are you sure the slot is defective?  My PCI slots 4&5 share an IRQ which
>could cause weird behavior under some circumstances.  Other boards that
>have built-in SCSI, sound, etc are known to share IRQ's with particular
>PCI slots.


>> I discovered (by trying to use it) that the last unused PCI slot in my
>> system is defective.  This forced me to add an ISA NIC (a 3Com 3C509B)
>> instead of the PCI device I had planned on.

>> The ISA NIC is working well.  I wonder, though, what the drawbacks are
>> compared to a PCI NIC.  This device is just attached to a cable modem,
>> which suggests that it will never be called upon to move more than
>> 3MB/second anyway.

Thats right, does the cable modem run on 100 base T ????? or 10 base T

So a 10base T card will more than do you, unless you want to throw away good
money??

So how can there be any drawbacks

Quote:>> Is interrupt latency higher with an ISA NIC?  Increased CPU use?  The
>> initial install involves more work because you have to specify the IRQ
and
>> I/O port address range.  Now that the installation is done, though, I'm
>> interested in runtime gotchas.

The initial install (if you turn off the PnP on the card) deosn't need any
parameters passed at all with these cards !!!
Quote:>> Thank you.

>> ***** Steve Snyder *****

>--
>direct replies substitute timothymoore for user name

>"Everything is permitted.  Nothing is forbidden."
>                                   WS Burroughs.

 
 
 

What are drawbacks to using an ISA NIC?

Post by Steve Snyde » Tue, 01 Jun 1999 04:00:00


1. I mis-wrote the expected top speed.  The cable modem moves a maximum of
3 megabits, not 3 megabytes, per second.  That should be well within the
capabilities of the ISA bus.  Sorry for the confusion.

2. That PCI slot is definitely defective.  Using a PCI NIC in that slot,
packets can be sent but not received.  I tried 2 different NICs in that
slot and examined all the IRQs in the system before deciding the slot was
bad.

Thanks for the response.


>ISA is clocked at 8.3MHz, PCI at 33MHz.  ISA has more CPU overhead too.

>This card is 10bT if I recall correctly, so it won't move more than
>about 850KB/s.  If you want 3MB/s you'll have to go 100bT which means
>PCI.

>Are you sure the slot is defective?  My PCI slots 4&5 share an IRQ which
>could cause weird behavior under some circumstances.  Other boards that
>have built-in SCSI, sound, etc are known to share IRQ's with particular
>PCI slots.


>> I discovered (by trying to use it) that the last unused PCI slot in my
>> system is defective.  This forced me to add an ISA NIC (a 3Com 3C509B)
>> instead of the PCI device I had planned on.

>> The ISA NIC is working well.  I wonder, though, what the drawbacks are
>> compared to a PCI NIC.  This device is just attached to a cable modem,
>> which suggests that it will never be called upon to move more than
>> 3MB/second anyway.

>> Is interrupt latency higher with an ISA NIC?  Increased CPU use?  The
>> initial install involves more work because you have to specify the IRQ and
>> I/O port address range.  Now that the installation is done, though, I'm
>> interested in runtime gotchas.

>> Thank you.

>> ***** Steve Snyder *****

>--
>direct replies substitute timothymoore for user name

>"Everything is permitted.  Nothing is forbidden."
>                                   WS Burroughs.

***** Steve Snyder *****