A500 Upgrades

[Oldsmobile_Mike]

Haha, watch out, it's a money pit!  

Just kidding, I'm in the middle of the same thing myself, too many years of pent-up nostalgia for my A500 system back in the early 90s.  After picking up a complete, working system (including 1084 monitor) for $40 off my local craigslist a few months ago, I proceeded to dump a ton of $$ into the system, but love it more every day.  A rough list of some of the upgrades I've done, which I could recommend (starting in the order I did them)

- 68010 processor ($5, ebay)
- Modify the 6A motherboard so it uses the trapdoor memory as chip memory for a full 1MB (just a bit of soldering, instructions online)
- External floppy drive ($10, ebay)
- Kickstart & Workbench 3.1 ($15, ebay)
- Kickstart switcher, 1.3/3.1 ($10-ish, ebay)
- Parallel port ADF transfer kit ($15-ish, ebay)
- ECS Denise ($20-ish, ebay)
- Indivision ECS ($100-ish, AmigaKit), upgraded to latest 1.10 firmware for 800x600x16 color screens
- GVP Impact Series II A500+, which I upgraded from 2MB of memory to 4MB, installed the latest 4.15 ROM, then replaced the original 80MB drive with a MechWare SCSI card reader and a 4GB Transcend CF card, also soldered the pads on the GVP motherboard so it draws power from the expansion bus rather than a separate PSU... all-told probably have $300+ in this unit alone, with all my mods
- External black SCSI CD-RW drive (scored this for the princely sum of $2 on ebay, although the 25-pin to 50-pin Centronics cable to hook it to the GVP cost an extra $8!), I've also done some mods to this unit
- Registered WHDLoad ($30 as I recall, worth every penny!)
- MegaChip, 2MB of chip ram ($80, amibay)
- VXL-30 25MHz accelerator with 2MB fast memory (just added this this morning, $200, amibay)
- 25MHz 68882 math co-processor ($12 + $2 shipping off ebay in Germany, think the seller has a lot more)

Think that about covers everything!  Of course everyone's system is individual and unique.  If you just want to build something to play a few games I'd stop at the first part of the list, add the 68010 to make use of the quit key in WHDLoad games (it's also about a 5% speed improvement) and throw a bit of extra memory in there - you've got 1MB now, you can do the motherboard mod to make your trapdoor memory seen as extra chip memory (which is a lot easier than soldering the extra chips onto the board), then maybe add an extra meg of fast onto the sidecar slot with something like the SupraRam, and that parallel port ADF transfer kit... some new floppy disks and an extra drive, you'd be good.

Really depends what you want to do though, add a sidecar hard drive for more storage, or check out that new ACA500 accelerator + CF hard drive interface coming out in a few weeks...  Or if you want to be able to use modern monitors the Indivision ECS is a beautiful piece of hardware...

In any case, good luck and have fun!  

[Oldsmobile_Mike]

I am wondering, as I have the same SCSI setup as you, did you have to do anything to the motherboard to hook up the external SCSI CD-RW, in the way of termination?  I am not sure about this unit, but, I know you have to unsolder the terminating resistors on the a2091.  I have an external SCSI CD-RW I'd like to hook up to mine, but have never tried it due to figuring I'd have to mod the motherboard termination to use it.

Thanks

Hi!

On the GVP motherboard, no I did not.  I just plugged the drive in and it worked right away (well, as soon as I installed and configured CD0: in my Devs/DOSDrivers directory, anyway).  The CD-RW had two external Centronics ports, I plugged the cable from the GVP into one and the large terminator (came with it) into the other.  It was configured as ID 5 (my internal HD was configured as 0) and I didn't have to change anything for it to work.

The fun came when I removed the hard drive and replaced it with the MechWare card reader, was tough wrapping my head around but eventually I got it working again by removing the external terminator on the CD-RW and installing a jumper directly on the back of the drive inside the housing ("Termination") and removing the "Term Power" jumper.  CD-RW is now configured as 2, card reader as ID 1.  All works fine, no mods needed to GVP board.  Let me know if you'd like me to post any pics or any other details!  

[Oldsmobile_Mike]

Just don't let Mike replace your Agnus and you should be okay.

LOL, considering how many people responded to that thread that they'd cracked the socket using screwdrivers, I think I did a pretty wizz-bang job of it!  A little chip in the bottom, hey, it builds character!  

[Oldsmobile_Mike]

The 6A most likely has an 8372A Agnus, which can address up to 1MB of chip ram.  By default your 512K on the motherboard is chip and anything you add into the trapdoor is "slow-fast", which pretty much means that the computer sees it as fast memory but it doesn't provide the speed increase that real fast memory (whether attached to the side expansion bus or the processor) does.  There's boards out there that let you add several megs into this trapdoor slot, but your best option is to convert that slow-fast into chip memory by soldering a couple jumper pads on the motherboard (this is much easier than adding the chips into those extra spots on the board).

Having 1MB of chip ram accessible to the custom chips will allow you to open more screens, load more samples, more graphically intense operations, etc., then you can add some real fast ram onto the side bus slot or under the processor (sorry I forgot, those Kipper2K cards are a great deal also!).

Here's instructions:

http://aminet.net/docs/hard/a500chip.lha


(or if you're reading this on a PC, you can open that LHA archive with WinRAR and the instructions doc with Word, that's what I did, LOL)

[Oldsmobile_Mike]

Re: the joystick, try some contact cleaner maybe?  Or just hunt on ebay, that's the one thing I forgot - my A500 didn't come with any joysticks so I spent a couple days trolling ebay, next thing I knew I had a box full of joysticks for $20.  Don't know what I'm even going to do with 'em all, but at least I've got spares!  ;-)

[Oldsmobile_Mike]

Ah yes, I see now.  You've got 4 but they are 4 x higher capacity than the 41256.
 
Just search for 424256, needs to be DIP package:-
 
http://www.ebay.co.uk/itm/D424256C-80-NEC-DIP-20-IC-/290458263493?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item43a0a95fc5#ht_63wt_1161
 
£5 each isnt too bad, but means £20 for the chips you need.
 
Then sockets:-
 
http://www.ebay.co.uk/itm/DIL-DIP-IC-Socket-6-8-14-16-18-20-Pin-Sockets-UK-1st-Class-Postage-/290767443526?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item43b3171646#ht_1897wt_1161
 
You need 20 pin DIP sockets, which that seller has.
 
Simply solder the sockets in place, stick your chips in and I think you are away.  There might be a jumper or something, I will check in a min.

I believe if you're going to go that route you also need to solder in the resistors?  Might want to double check...