23/02/95 Archive maintainers note: ------------------------- The article below was not actually published in Acorn User, however it is included here for reasons of completeness and for its useful information. Dave Walker The Acorn Archimedes 400/1 series and the older pre June 1989 440 systems both had a Hard Disc interface designed and built on the PCB (Printed Circuit Board). On the Acorn Archimedes 300 series system Acorn offered the Hard Disc and Controller Expansion Card as an additional, optional upgrade. The interface type that has been supplied by Acorn for all the above systems is ST506 MFM (Modified Frequency Modulation). ST506 is the standard that any Disc Disc fitted to the system must conform to. It is possible to upgrade all the above systems to access two Hard Discs. The Hard Discs are not supplied by Acorn and will need to be externally powered. Acorn Archimedes 400/1 Series Approximately half way up the left hand side of the PCB (facing from front to rear of the machine, the backplane will need to be removed before a clear view of the sockets will be seen) are three sockets labelled SK8, SK10, SK11. SK11 is a 34 way socket into which the CONTROL cable is plugged and then runs to the Hard Disc. SK10 is a 20 way socket into which the DATA cable plugs and then runs to the Hard Disc. SK8 is a spare 20 way socket which used used to run a separate DATA cable to the second Hard Disc. The 34 CONTROL cable should be daisy chained to run to both the internal and external Hard Discs. The interface is normally linked to support up to eight heads per drive, by changing both LK12 and LK13 from the set position to their alternative position, up to 16 heads can be supported. This action removes the reduced write current capability, but this tends not to be used externally by larger capacity Hard Disc units. The Archimedes system will then require reconfiguring to show this second Hard Disc icon on the icon bar, the configuration command required is *CONFIGURE HARDDISCS 2. The Hard Disc will then need to be formatted. Acorn has always supplied a copy of the Hard Disc formatter 'HForm" with all systems. 440 Systems Much of the information required for the pre June 1989 440 systems is identical to the 400/1 system upgrade. The differences lye in the cable sockets and the link numbers. The two sockets used for connecting the Drive 4 Hard Disc are SK10 for the CONTROL cable and SK9 for the DATA cable. The seprate socket in which the DATA cable that runs to DRIVE 5 is numbered SK8. The two links that require altering are LK3 and LK4. LK3 should be set EAST and LK4 should be set WEST. The other details regarding the daisy chaining of the CONTROL cable is the same as above. Also the details of regarding reconfiguring and formatting of the hard Disc are the same as above. 300 Series (AKD52) Hard Disc Upgrade Expansion Card The cabling system applies equally to the 300 series upgrade. The socket for the CONTROL cable is labelled PL3 and the socket for the DATA cable is labelled PL4, however unlike on the other systems the extra 20 way DATa cable socket is not fitted to the board as standard although there is space for it. The link numbers that require altering are LK4 and LK5. The Molex pins a jumpers should already be fitted and therefore just require moving to their opposite positions which will be LK4 EAST and LK5 WEST as you look at the card installed in the machine with the backplane neareat to you. All the other details regarding configuration and formatting remain the same as the other systems. NOTES 1. It should be noted that it is necessary to have RISC OS fitted to any system that these modifications are carried out on, as ADFS in Arthur (Arthur is the previous operating system fitted to Archimedes systems before RISC OS) does not support 2 Hard Discs. 2. It is recommended that Hard Disc of an access time of 28ms (ms = Milliseconds) are fitted to machines. 3. Acorn Computers Limited cannot accept any liability for any loss or damage arising from the use of any information or particulars documented in this article. 4. Acorn recommends that if you are at all unsure abut carrying out these modifications that you contact your local Acorn Authorised dealer who is versed in the servicing of Acorn systems and will therefore be able to make all the necessary modifications required.