RE: D9060 Help Needed

Date: Mon, 7 Dec 2009 02:08:58 +0100 (CET)
Message-ID: <19089216.2011451260148138683.JavaMail.www@wsfrf1227>
Hi ...
Just reading this - Did anyone tried to directly use a SCSI 1 HDD in place of the SASI->MFM card ?

PS : A good source for 4 plates MFM HDD are Atari megafiles .... that costs nearly nothing on eBay.


SCSI and SASI are similar, in fact a the beginning SASI and SCSI were the same
Only the name changed. Later scsi evolved..

If you can find some SCSI I document it should work with a 9090 / 9060

In short the data SCSI I / SASI is a kind of bidirectional parallel port
There are 2 wires called REQ / ACK that are responsible of the data transfers
A wire called IO indicate the direction of the transfers.
C/D indicates if command or data are transferred

Another signal (forgot the name), was indicating the end of the command

There are several kind of commands
I don’t remember the exact command with the code associated
But I cant try to remember / find some documents

It was something like that 

00 check drive ready
01 read
02 write
03 ???
04 format

There are several set of command some short 4 bytes (don’t remember very well)
And somme long like 10 bytes

As far as I can remember it started like that

Signal select + 1 bit of the data set to 1 to select a device 
Device 1 to 8 or 0 to 7 sorry can't remember

Then C/D + I/O where asserted to COMMAND / OUTPUT (sorry not sure)
Then REQ from the disk then the 1st data byte of the command 
Then you had to assert ACK (not sur but still the same, verify on scsi 1 specifications)
Then all other byte of the command were sent with same mechanism
The C/D went from C/TO D and you had to send / receive the data
With the same req/ack mechanism

At the end a status byte (not sure how it worked)

I was able to connect the 9090 to direct sasi
Card, it worked without any problem.

-----Message d'origine-----
De : [] De la part de
Envoyé : lundi 30 novembre 2009 15:20
À :
Objet : RE: D9060 Help Needed

Hallo Jim,

> and any subsequent command gives "74, DRIVE NOT READY..."

At one time I had four 9060's and one 9090 at my place. Only one had a
working (what I call) "middle board" (the board is in the middle,
between the hard disk and the CBM board, the one equiped with the two
6502's). This middle board translates the SASI signals coming from the
CBM board into MFM. Just have a good look at it and you understand why I
didn't think about even to try to repair it.

This board is also the reason why I disassembled FDC-ROM to find out how
the SASI protocol works. The idea behind it is quite simple: replace
this "middle board" with a micro-controler and an IDE hard disk or SD
card. But so far I wasn't able to understand the protocol :( For those
who say "SASI is like SCSI", I know, but this knowledge didn't help me
very much.

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Received on 2009-12-07 02:00:04

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