Date : Wed, 01 Oct 2003 15:09:14 +0100
From : Andrew Hancock <Andrew.Hancock@...>
Subject: Re: BBC Micro lazy delayed boot!
> -----Original Message-----
> From: Sprow [mailto:info@...]
> Sent: 01 October 2003 14:17
> To: 'bbc-micro@...'
> Subject: Re: [BBC-Micro] BBC Micro lazy delayed boot!
>
> In article
> <6A4F555CEA3CD5118DBD0002E30AC0912C0854@...>,
> Andrew Hancock <Andrew.Hancock@...> wrote:
>
> Hi,
>
> [snip]
>
> > > >1. Outputs of IC 16
> > >
> > > All normal.
>
> Good.
>
> [snip]
>
> > > >WITHOUT 8271 installed.
> > > >
> > > >As above.
> > > >
> > > >Except IC 1 6502
> > > >
> > > >Pin 6 NMI PERMANENTLY LOW No transition observed.
> > >
> > > No, this is wrong. It should be pulled high by R81. Check this for
> dry
> > > joints. If ic27 is socketed, does it go high if ic27 is taken out?
> > > What is the status of link S2?
>
> A partially yanked out disc interface would cause this because of the
> inversion from IC27 (PC chips are usually active high interrupts).
> This is the purpose of S9: if you remove the disc interface you need to
> fit
> it to ensure the output of IC27 is high.
>
> [snip]
>
> > If DFS 0.9 and 8271 are installed, the machine still delays for 15
> seconds
> > at power-on, but rather than displaying a flashing cursor, it displays
> the
> > full
> >
> > BBC Computer 32k
> > Acorn DFS
> > _ flashing cursor here, long beep for 15 seconds then
> > BASIC
>
> With DFS 0.9 the absence of a disc when attempting to *CAT can't be
> Escape'd
> from (it should timeout with a disc error if you wait long enough).
> I might have missed it,but what's the state of nNMI and nIRQ during the
> 15s
> long pause?
>
> If one of the two is jammed on then almost all of the processor time will
> be
> spent entering and leaving the interrupt handlers - you can see the affect
> this has by reading the "Slower Downer" article on my webpages,
> Sprow.
DFS 0.9 Installed
8271 FDC Installed
No floppy drive connected
*CAT results in the following after 0.5 second
Disk fault FF at 00/FF
what's the state of nNMI and nIRQ during the 15s long pause?
Is this Pin 4 and Pin 6 of the 6502 CPU IC1?
Regards
Andrew