Re: Track/Sectors for older Drives, eg D9090

From: Marko Mäkelä (
Date: 2003-08-26 08:07:09

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Date: 25 Aug 2003 23:18:23 +0100
From: "Jacob Dahl Pind" <>
Message-ID: <>
MIME-Version: 1.0
Subject: Re: Track/Sectors for older Drives, eg D9090

on 25-Aug-03 09:53:07, ncoplin wrote:

>Hi All,

>I'm a little confused about the track/sector information given by various
>sources (including the Inner Space Anthlogy) for some of the older drives.
>They talk also about cylinders... and that confuses me.

>What I'm after is "logical" info, that is the layout a programmer would use.
>I am thinking that the D9090 is laid out as: 918tracks (1-918), 32 sectors
>(0-31). etc.

>Can someone confirm this, and also the layouts of the other drives of this
>era? is there a standardised detection routine for the D9060/9090? It seems
>you can stick any mechanism in the box and it will work... but...

>Regards, Nick

The following is taken from Commodre Disk referance manuale for D9090 D9060
8250 8050 4040 2031.

Model					D9090		D9060
heads per drive				6			4
formatted storage
capacity per unit		7,47Mb		4,98Mb

cylinders(tracks)		153			153
sectors/cylinders		128			192
sectors per track		32			32
blocks per sector		256			256

it doesnt say anything about how to detect 9090 or 9060, but a quick look at
its bam and then simply count how many BAM sectors you encount, should do the

D9060/9090 BAM block format 0 track 1 sector 0 (normal location)

Byte		Date		Definition
0-1				Track-sector pointer to next BAM block
				(hexdecimal $FFFF = last bam block)

2-3				Track-sector pointer to privious bam block
				(hexdecimal $FFFF = first bam block)

4				lowest track # mapped in the BAM block

5				Higest track #(+1) mapped in this bam block

6				nummber og blocks unused on the track

7-10				bitmap of avaliable blocks on this track

11-255				bitmap of next 49 track

Someday I`ll get that Commodre Disk referance manuale for D9090 D9060
8250 8050 4040 2031 OCR scanned.

Regards Jacob Dahl Pind

		CBM, Amiga,Vintage hardware collector

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