Re: The Jumperless Pentium Mainboard

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Article #2031

#2031

From: Richard RUDEK
Date: Tue, 19 Nov 1996 00:00

26 lines
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"Peter E. Fry" <pfry@cyberramp.net> wrote:

>Videoman wrote:
>> Like everything else in the PC's "design", it's a bit screwed up.
>> Technically, the PC could support 64 IRQs using the same PIC chip that
>> it does now. The problem is, where do you put the IRQ lines on the bus
>> connectors? That's a lot of pins.

>  64 (or even 63) IRQs with two 8259s?  How?  And with level triggering
>available, why?  Edge triggered interrupts was a cost-related decision
>on the original PC, and a mistake, as it turns out.  But as far as I
>know the 8259 has eight channels, period.

[snip]

Cascading. The PIC has a private cascade buss: CAS0->2. Initialisation
command words can program a PIC to be a Master or a Slave PIC.

Problem is that both Slave and Master PIC's have to be sent EOI
commands. The AT already does anyway, but it is a chore.

  __   __   _______________________________
 //)) //)) | Richard RUDEK. MicroDek.      | Hey, Whadda ya
//\\ //\\  | Chatswood, Sydney. Australia. | want for nuting...
           `-------------------------------'

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<55j9q4$dtf@voyager.iii.org.tw> <32825a4d.6217654@NewsServer.cc.monash.edu.au> <32838f5c.910767@news.escape.ca> <32851A7B.7F5E@ix.netcom.com> <328520E4.215D@lehigh.edu> <32865b6a.585145543@news.zip.com.au> <3286A74E.5656@lehigh.edu> <3286F48B.2829@ocean.com.au> <328ab895.871183655@news.zip.com.au> <328BF96B.27BE@ocean.com.au> <1996Nov15.123714@eos.hitc.com> <328D54D3.5B77@ocean.com.au> <3290D06E.38DB@tiac.net> <32910690.3FE2@cyberramp.net>

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From: rrudek@zeta.org.au.NoJunkMail (Richard RUDEK)
Subject: Re: The Jumperless Pentium Mainboard
Date: 1996/11/19
Message-ID: <56sc3q$oqs@phaedrus.kralizec.net.au>
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references: <55j9q4$dtf@voyager.iii.org.tw> <32825a4d.6217654@NewsServer.cc.monash.edu.au> <32838f5c.910767@news.escape.ca> <32851A7B.7F5E@ix.netcom.com> <328520E4.215D@lehigh.edu> <32865b6a.585145543@news.zip.com.au> <3286A74E.5656@lehigh.edu> <3286F48B.2829@ocean.com.au> <328ab895.871183655@news.zip.com.au> <328BF96B.27BE@ocean.com.au> <1996Nov15.123714@eos.hitc.com> <328D54D3.5B77@ocean.com.au> <3290D06E.38DB@tiac.net> <32910690.3FE2@cyberramp.net>
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