Hello, Victor, Dave and all,
I read your comments below, and sorry to ask such a lo tech question, but
am planning to do a machine control RTL project (with EMC if you should know
it). With respect to hardware, I will be building a 366 or 400 Mhz MB Intel
architecture machine. What's an appropriate bus if not ISA for RTL? Or,
what's a good MB to use for a non-demanding and non mission critical RTL
application. This machine will not be RTL dedicated. I have thought about
dual processors for reasons other than RTL, but don't know how desirable they
would be to RTL.
Victor Yodaiken wrote:
> On Sat, Jul 10, 1999 at 04:15:51PM -0700, David Schleef wrote:
> > On Fri, Jul 09, 1999 at 07:47:56PM -0600, Victor Yodaiken wrote:
> > Personally, I think it is a hideous hack to use an 8254 in one-shot
> > mode, an/or to use the ISA bus on a 400 Mhz computer. And I've not
>
> what's really immoral is that non-x86 boards are being made with
> isa-bus 8254s as timers.
>
> > had someone show me that the IO-APICs are actually capable of decent
> > timing. IO-APICs have been on motherboards for several years, yet
> > Linux still does not have an earliest-deadline first timer interrupt
> > except with the UTIME patch, which uses the XT-PIC.
>
> See beta 10, to be released in a couple of days.
> The APIC timer is an on chip timer connected to the pentium "Advanced"
> PIC. The io-apic is off chip. SMP intel design uses
>
> i/o/devices -> io-apci -------serial irq bus----
> |
> on chip apic
>
>
> On non-smp motherboards, evil board designers _disable_ the apic
> so that the apic timer cannot be used. But, Manoj and others have
> discovered that the apic timer is available on smp boards, even when only
> one processors is installed. However, I don't think it makes things
> so much better, unfortunately. We'll see if tuning helps us.
>
> > timers are not adequate, since you might miss any number of timer
> > ticks between when you get the interrupt and when you reprogram
> > the timer, even if you have low latency.
>
> APIC is fast enough so that we treat it as one shot, even though we
> always leave it periodic.>
> >
> > dave...
> >
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Dick Skaggs
Orlando
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