Date   : Wed, 15 Mar 2006 10:39:02 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: SASI/SCSI <>IDE, distracting thoughts.

John Kortink wrote:
> On Tue, 14 Mar 2006 23:55:02 +0000, Andy Armstrong wrote:
> 
>> On 14 Mar 2006, at 21:50, Jonathan Graham Harston wrote:
>>> IDE interface: two ICs minimum.
>>>
>>> SCSI interface: six ICs minimum and lots of bus spaghetti.
>> I have upstairs somewhere a SCSI interface I designed (HCCS SCSI  
>> Micropodule) which is I think two chips, maybe three. It's an 8490  
>> and not much else if I remember rightly.
> 
> So, redesign it for the beeb and satisfy the SCSI
> craving patrons of this list. ;-)

heh heh. It's purely a software problem as I see it - the Acorn "SCSI" 
controller is OK, or would be with some sort of (dummy or otherwise) parity 
mod. Plus it's all built with TTL chips that are easily scrounged from dead 
old equipment; I'm not sure what the availability of the 8490 chip would be like.

Problem AIUI is that ADFS just won't cope with anything other than 256 byte 
sectors at the lowest level (although isn't the ADFS filesystem format 
permanently fixed at 256 bytes/sector too?)

Out of interest, how's this been addressed with the various IDE projects out 
there? Presumably IDE drives have the same sorts of problems, and are probably 
fixed at 512 bytes/sector without a LLF? Is half the disk being thrown away, 
or has ADFS been patched so it can address a high/low half of a 512 byte 
sector as a 256 byte one?

cheers

Jules