From: robtu@itx.isc.com (Rob Tulloh)
Subject: Mega-Midget Racer install on Amiga 500 - Notes
Summary: I had some problems installing the board on my A500
Keywords: Amiga 500, MMR, CSA, Mega-Midget Racer, accelerator, 68030
Organization: Interactive Systems Corporation, Boulder, CO
Date:  7 Apr 92 00:59:20 GMT

Hello World!

I recently installed a CSA Mega-Midget Racer board in my Amiga 500 and
I wanted to pass along a few items I feel might be useful to those
souls out there considering a purchase of this product or who may be
in the same boat I was in last Friday night with my new board in hand.

A little background. I followed the installation instructions in the
CSA docs religiously. With the cover off my machine, everything booted
(except for a problem with my DRAM board), and looked to be OK. However,
I put the machine back together and blam! Dead. Nothing. Nada. Zippo.

-----

The problem has to do with parts of the MMR board which touch the
inside of the Amiga. More exactly, places where the MMR touches the
metal shield which covers the Amiga 500 mother board.

The problem turns out to be 2-fold. If the MMR board comes shipped
with a sacrificial 68000 socket attached to it, it will be too tall
for the 500's limited space under the internal metal shield. Any parts
of the MMR board which touch the metal shield will undoubtably cause
the board not to function, and the machine to go belly up. The extra
socket is shipped with the board to protect it's pins during shipment.
It also serves a purpose to raise the MMR board if you have other
3rd party products which must fit under the MMR.

If the board does not have the sacrificial 68000 cpu socket attached,
or you remove it, you will still have problems with the left front
corner of the board touching the metal shield and/or keyboard. The 1st
2 pins which come up from the 68000 socket to the MMR board will make contact 
with the metal shield thereby disabling the board.

-----

Here is a list of things I put together regarding installation of the MMR
on an Amiga 500. I have checked all these things with CSA who said that 
these are all OK. Hope it helps!

Signs of shorted/grounded/non-functional MMR:

1. Machine is dead. Power light does not come on at all. 3-finger salute
   does not even illuminate the capslock key.

2. Power light comes on very dim, screen flashes purple/yellow or does
   not flash at all. Machine may start to boot and then die during boot
   or shortly after.

3. With cover and metal shield off, position of keyboard seems to
   affect how machine works. Striking a key suddenly fries the
   machine.

Checklist of possible fixes:

1. 68000 feed pins touching the metal shield need to be insulated by cutting
   the metal shield away and/or using electrical tape to buffer the pins which
   are exposed on the MMR from the metal shield. The feed pins are located 
   at the left front corner of the board.

2. If you have a stock/un-modified A500, take off the sacrficial socket
   adapter (i.e. you don't have any other 3rd party products in your
   machine). Don't be afraid to use a *little* force to seat the MMR
   board on the A500 motherboard. It does not sit completely down in the
   mother board socket like it does the sacrificial socket, but it will
   snap into place.

3. Use vellum and/or electrical tape to protect places on the metal
   shield where MMR chips might make contact. Check the chip/plug in U6
   and any oscillator in U5 (if it is as tall as the thing in U6 - I
   don't have one), to see if the metal shield (when compressed by the
   replacement of the outer cover) might touch.

4. If the sacrificial socket is needed to raise the board height for 
   other products, you will need to make holes in the metal shield to
   allow the MMR components to operate without accidental grounding
   on the metal shield. According to CSA, you can remove the metal shield
   entirely from the machine if you like.

5. If the board fails to operate after all the above steps, you might
   need to check the board voltage to ensure it is within the
   critical 5v +- .15v range. I am told the stock Amiga 500 power supply
   has a pot adjuster which will allow you to modify the amount of
   current delivered by the power supply.

-----

On my machine....

1. The height problem of the board was mostly eliminated by removing
   the sacrificial CPU socket from MMR plug. After removing the unneeded
   socket, only the SYS chip in U6 was threatened and I used black electrical 
   tape to protect it. I applied the tape to the underside of the metal 
   shield just above the chip/plug in U6.

2. I used tin snips to prune away a small section of the metal shield
   which would interfered with the feed pins on the left front corner
   of the MMR board.  I taped the edges of the metal shield with black 
   electrical tape and then put a protective piece of tape over the first 
   few pins on the MMR board so that nothing could accidentally make
   contact with them (keyboard/metal shield) would not hit them.

All in all, I am satisfied with the support I got. I wish the folks at
Memory World or CSA had included info with the product which stated the
pitfalls for A500 users. If I had known about the shorting problem,
I could have saved myself hours of hassle. A sheet of tips for A500
users would be worth a lot. 

I will be even happier when the DRAM board shipped with my MMR is
working (CSA believes a software problem and are sending me an update).

Maybe I'll submit this list to CSA and/or Memory World as additional 
installation notes. Anyone else want to add to the list?

I have to credit everyone I got e-mail from for the things on the list.
None of this would have been possible without them.  Having a usenet/email
connection can sure save the day!

Rob Tulloh
--
INTERACTIVE Systems Corp.         Tel: (512) 343 0376 Ext. 116
9442 Capital of Texas Hwy. North  Fax: (512) 343 1414
Arboretum Plaza One, Suite 700    Net: robertt@isc.com (polled daily)
Austin, Texas 78759                    robtu@itx.isc.com (same thing!)