Subject: Re: Linux on CD

From: Andy Armstrong <[email-masked]>
Date: Wed, 20 Aug 97 08:18:35 +0100

>> The 16 bit card has a NCR 53C94 or equivalent. The hardware of that card 
>> is involved...
>
>How involved - there is generic NCR5380/9x/400 support in the Linux kernel
>that you basically provide the low level bits too

Oh, probably not that bad then. There's a bit of logic (4 pals) which 
implement a MEMC state machine with a timeout, the idea being that you 
can blat away at the chip without doing any handshaking; you get 
interrupted if a timeout occurs. You can however ignore that and just 
poll the FIFO on the chip. I assume that's an option which already exists 
in the code.

I'm quite happy to let people look at the source. It's old and convoluted 
and nasty and largely free from comments, so business as usual there :-)

-- 
http://www.wonderworks.co.uk --> Free RISC OS software
Andy Armstrong

---

From: Alan Cox <[email-masked]>
Date: Wed, 20 Aug 1997 10:58:35 +0100 (BST)

> poll the FIFO on the chip. I assume that's an option which already exists 

That sounds reasonably sane. The Linux driver base supports

1.	Polled I/O on the NCR5380/94 - thats best described as "treacle 
pudding mode".

2.	Pseudo DMA - which sounds like your state machine handles. The only
problem we've had there is the Mac - instead of an "it failed" interrupt
it bus errors on a timeout/disconnect and the bus error is a pig to clean
up ;)

3.	Real DMA - which is not relevant in this case.

Alan