PC20-III IDE interface

From: Baltissen, GJPAA (Ruud) (ruud.baltissen_at_abp.nl)
Date: 2003-11-21 15:12:00

Hallo allemaal,

I'm still busy with disassembling the ROM of my PC20-III. The reason why I
started this work was to find out how I can replace its HD with another
type. The only thing I can say is that until now it makes no sense :( AFAIK
it only uses four I/O addresses: 0320h..0323h, not the six I expect for a
normal IDE-HD. Even stranger is the following code:

; [AA79]
FillDX322_326	proc	near
			push	cs
			pop	dx			
			cmp	dh,0FAh		; CS = $FAxx? 
			mov	dx,322h
			jz	loc_AA86		; yes, ->
			add	dx,4			; DX := $0326
			in	al,dx			; port 326h 
FillDX322_326	endp

The value used to fill DX depends on wether CS = 0FA00h or not! The only
time I know CS is 0FA00h is right after a reset when the PC is scanned for
"external" ROM with the well known "55 AA" identification code. For the
rest, I havent the faintest idea. The only thing I can think of adding
another IDE-interface with its own _same_ ROM which is executed on another

Other info: AFAIK the interface is initialized by writing 6 values to the
same I/O address. This sounds like initializing a floppydrive. The only
thing I can imagine is that C= developed a floppy-like interface that on its
turn outputs IDE-signals. Any comment on this subject is very welcome.

PS: I have some vacation for a week so it is possible I won't react on react
on amy email untill december 1st.

   / __|__
  / /  |_/     Groetjes, Ruud
  \ \__|_\
   \___|       http://Ruud.C64.org


De informatie in dit e-mailbericht is vertrouwelijk en uitsluitend bestemd voor de geadresseerde. Wanneer u dit bericht per abuis ontvangt, verzoeken wij u contact op te nemen met de afzender per kerende e-mail. Verder verzoeken wij u in dat geval dit e-mailbericht te vernietigen en de inhoud ervan aan niemand openbaar te maken. Wij aanvaarden geen aansprakelijkheid voor onjuiste, onvolledige dan wel ontijdige overbrenging van de inhoud van een verzonden e-mailbericht, noch voor daarbij overgebrachte virussen.

The information contained in this e-mail is confidential and may be privileged. It may be read, copied and used only by the intended recipient. If you have received it in error, please contact the sender immediately by return e-mail; please delete in this case the e-mail and do not disclose its contents to any person. We don't accept liability for any errors, omissions, delays of receipt or viruses in the contents of this message which arise as a result of e-mail transmission.

       Message was sent through the cbm-hackers mailing list

Archive generated by hypermail pre-2.1.8.