Here is my A500+ specs:
2 megs chipram (soldered on motherboard)
Derringer 68030@50mhz 68882@50mhz 32megs 32bit fastram
Supra 500XP+ with 300meg SCSI drive and 2megs 16bit fastram
First of all, when considering a 68000 socket mounted accelerator, there are some definite mounting issues to consider. Most of these type of accelerators (the derringer included) have no provision for securing the card other than sitting in the 68000 socket and possibly having some rubber feet that rest against the motherboard. To make matters worse, there is very little (if any) clearance between the top of the accelerator and the keyboard assembly. If you dont have a VERY GOOD TIGHT connection where the pins of the accelerator plug into the 68000 socket, then anything from a moderate bump of the computer desk to vigorous typing on the keyboard can cause all manners of gurus, system lockups, spontaneous system resets, and general operational flakiness. I was able to fabricate a plastic bracket that bolts over the 68000 socket, and maintains moderate downward pressure on the Derringer, keeping it firmly seated in the 68000 socket, but there is barely room for this, and it took quite some work (half a day) to carve this thing out of plastic in exactly the shape it needed to be. It bolts to the 2 motherboard screw holes that are on either side of the sidecar expansion bus connector.
Secondly, with this type of accelerator, there is no room underneath it for a kickstart switcher board to reside in the rom socket. Some manufacturers have made kickstart switcher boards that hang on the end of a long ribbon cable (which in turn plugs into the ROM socket) for this purpose. I dont like the idea of hanging my system ROMs on the end of 8 inches of ribbon cable. I dont think this is a good step forward in the way of system stability.
For an A500 (or any OCS/ECS machine) it is often advantageous to be able to boot with Kickstart 1.3. Most of the floppy based games/demos that run best on these machines expect Kickstart 1.3. Kickstart "degrader" utilities work in some cases, but not all.
There are two possible solutions to this. First, you can put a 1.3 kickrom in the rom socket, and just employ a "soft-kicker" in your startup sequence on your hardisk. This way, when booting from floppies, you have kickstart 1.3, and when booting from the hardisk, the 3.1 kickstart image is loaded into a 512k chunk of fastram which is then remapped as the system ROM, allowing Workbench 3.1/3.9 to load and run correctly. I have done this in the past with many AMIGA systems, and it even works rather well with a stock 68000, despite the absence of an MMU. Unfortunately, I am unable to find a softkicker that works correctly using the Derringer's fastram.
The second possibility is to burn BOTH kickstart images onto a 1 megabyte EPROM and hook a switch between the highest adress line and ground, allowing it to "float hi" when the switch is open. This takes no more physical space than a standard Kickstart ROM, and allows you to switch between the upper and lower 512k of the EPROM (on which you will have your 1.3 and 3.1 kickstart images burned, respectively). I would like to avoid having to do this if possible, but so far it seems to be the only alternative.
Lastly, I'll say that the 2 megs of 16bit fastram which resides on the Supra Controller does work with MANY "soft-kicker" programs, but I have this ram disabled because it does not work (hangs the system on reset/bootup) with the Derringer installed. Also, I'd like to avoid using 16bit fastram if possible, for obvious performance reasons.
Anyone dealt with this issue before? Can you reccomend a softkicker that works using Derringer 32-bit fastram?
Anyone know of someone who makes custom dual-kickstart EPROMs? I do own MANY original kickroms of both the 1.3 and 3.1 variety, so there are no legality/licensing issues here.
Any advice is appreciated.
Thanks.
