Re: How to transform a Disk II card to handle 13-sec?

[dempson@actrix.gen.nz (David Empson)]

Toinet <antoine.vignau@laposte.net> wrote:

> Hi There,
> I recently purchased a set of 2 "boards" which allow to switch from a
> 13-sec to a 16-sec format (http://cgi.ebay.com/ws/eBayISAPI.dll?
> ViewItem&item=310290628060)

The detailed photos aren't available for some reason, so it is hard to
confirm some information.

> As I own two Disk II controller cards, I would like to move the 13-sec
> chips from the above switch card to one of the Disk II controller
> cards but I need help.
> 
> IIRC (because I am unable to get the exact page on hackzapple.com),
> there are two chips that must be changed (the bootstrap ROM and the
> LSS ROM) but two questions arise:
> - which ones should I move? I don't know if the info given on the
> auction page is correct

They only mention one set of PROMs (P5). Without photos, it is unclear
whether the second card has the other PROMs, or is another pair of P5
PROMs.

One of the PROMs contains the 256-byte firmware which appears in the
$Cn00-$CnFF area. The other is the logic state sequencer which is the
heart of the controller mechanism. You need to change both of them to
get a genuine 13-sector controller.

> - once changed, is that sufficient? I mean, will I get a 13-sec Disk
> II controller card?

The only difference between the 13-sector and 16-sector versions of the
Disk ][ controller are the contents of the two PROMs (P5 and P6).

See the description in the FAQ for csa2 (part 9, Q17):

From: Neil Parker 

017- How does one distinguish between a 13 and 16-sector Disk ][ 
     controller card? 

     For a while at least, new 16-sector Disk II cards shipped with a
little white circular sticker depicting a red Apple with the number "16"
in the middle. 

     But the sticker is hardly a reliable test.  A better test is to
look look at the part numbers of the P5 PROM (the lower left chip on the
card) and the P6 PROM (left column, second from the top). 

          13-sector    16-sector 
          ---------    --------- 
     P5   341-0009-xx  341-0027-xx 
     P6   341-0010-xx  341-0028-xx 

The 16-sector PROMs may also be labelled "P5A" and "P6A". 

A program can test the card type by looking at its slot ROM space.  The
signature bytes are as follows: 

     $Cn01: 20 
     $Cn03: 00 
     $Cn05: 03 
     $Cn07: 3C 
     $CnFF: FF if 13-sector; 00 if 16-sector 

For example, 

     1  REM Scan the slots for Disk II interfaces 
     2  REM By Neil Parker 
     10  FOR S = 1 TO 7 
     20 A = 49152 + 256 * S 
     30  IF  PEEK (A + 1) <  > 32 OR  PEEK (A + 3) <  > 0 OR 
        PEEK (A + 5) <  > 3 OR  PEEK (A + 7) <  > 60 THEN 100 
     40  PRINT "Disk II ("; 
     50 T =  PEEK (A + 255) 
     60  IF T = 0 THEN  PRINT "16-sector";: GOTO 90 
     70  IF T = 255 THEN  PRINT "13-sector";: GOTO 90 
     80  PRINT "other"; 
     90  PRINT ") in slot "S 
     100  NEXT 

-- 
David Empson
dempson@actrix.gen.nz