Eyetech Group Ltd

Amiga Technical Notes

    
Fitting 3.1 ROMs
To replace your 3.0 ROMs with 3.1 ROMs you must first remove the 3.0 ROMs. To do this you must have access to the motherboard. If your A1200 is still in it's original plastic case then you must disassemble it (see dismantling your A1200). Once you have access to the motherboard locate the two Rom chips. They are just to the left of the trapdoor edge connector, near the front edge of the motherboard. Use a small flat blade screwdriver to lever the chips out as shown below.

The following shows the ROM sockets after the 3.0 ROMs have been removed. Please note that each socket has 42 contacts and the roms only have 40 legs.

When fitting either 3.0 or 3.1 ROMs you must ensure that the ROMs ar fitted with 2 empty contacts to the left ( )

Eyetech supply 3.1 ROMs with white labels fixed to the surface of the ROMs to indicate the orientation and location each ROM should be fitted. It is very important that the right chip is fitted into the right socket - U6a and U6b are different! Chips marked 391774 should be fitted into U6b , closest to the rear of your motherboard. When fitted correctly they should be as follows.

Please be very careful when fitting new ROMs. It can cause damage if either the ROMs are fitted with the unused contacts to the right instead of the left or they are fitted the wrong way round. i.e. the notch ( shown on the left of each chip in the above photos ) is facing to the right instead of the left.

Common Problems

It is very easy to fit the ROMs and bend one of the legs of a chip underneath. It may look to be OK but will usually not work at all or may cause errors / crashing. If your A1200 does not work when you have fitted the ROMs carefully remove them and check that all legs are straight. If one or more were bent carefully straighten it / them. The legs of the chips are usually strong enough to withstand being bent and straighten , but take care as if it happens too often they may weaken and break off. If this happens new ROMs may need to be purchased!

If you do not find any bent legs then carefully inspect the contacts inside the sockets on your motherboard. It is also possible to bend / distort the contacts inside the socket. For the ROMs and your A1200 to operate correctly all of the contacts are necessary. If a bad connection is occurring between the ROM and the socket you will get errors or your system will not boot at all. This may explain why if you fit a new set of ROMs they do not work the first time, but if you remove and refit them correctly again they will then function.

Notes:

The A1200 uses different ROMs to those use in the A4000. They have different memory address's for the IDE port and therefore may should you the disk insert animation but will not boot to an IDE HD.

Also the 3.1 ROMs have some different characteristics to your previous 3.0. Firstly they can take substantially longer than your original 3.0 ROMs. If you have no HD fitted it may take upto 30s before you see any activity at all, it should then attempt to access your floppy drive and continue. The ROMs wait this long whilst trying to find a Hard Drive to boot from, if a Hard Drive is found then it will boot. If a HD is present and working it will boot and soon as it is found - it should not take as long before starting booting.

E&OE