Date   : Thu, 08 Jan 2004 23:25:56 +0000
From   : Mike Tomlinson <mike@...>
Subject: Re: IDE Interface for BBC

In article <4c6dc16465info@...>, Sprow <info@...> writes

>The problem now is that harddrives are too big, and in order to coax BIOS'
>they falsely claim they're 4G drives. The beeb will need to have a load of
>interrogation code to work out their real size, or just give up and assume
>it's a 4G drive.

There's lots of small (<2Gb) 2.5" IDE drives floating around used from
PC laptop upgrades.

[5v current draw]

>Eek! Please look at the current requirements from 5V, especially the surge
>required to spin the drive up.

I said 2.5" /laptop/ drive - hard to believe this would take more than a
couple of 5.25" floppy drives hung off the Beeb's auxiliary PSU.  500mA
max spinning up sounds about right, perhaps 250-300mA quiescent.

Anyway, you haven't seen the inside of my Beeb [1].  Those Astec PSUs
don't half take some abuse :)

>Also, you'd need to support two IDC cable densities as laptop drives use
>finer wire and smaller connectors.

I may not have made this clear - I suggested the interface provide a 40
way IDE conenctor at the standard pitch so that either externally-
powered 3.5" drives /or/ 2.5" drives using a low-density to high-density
adapter cable could be used.  Those are freely and cheaply available.

Mike

[1]  BBC B, Econet, speech upgrade, ATPL Sidewise (fully populated with ROMs, 2x
static RAMs and battery backup), Watford 32k Shadow RAM board, Watford 16k
battery-backed Disc RAM board, Torch Z80 second processor card, all inside the
Beeb's case running off the original PSU. :)