Amiga.org
Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Laughy on April 04, 2013, 05:18:12 PM
-
Hello,
I've got my Amiga A500 running, (thanks to GadgetUK), it has a 512K trapdoor expansion.
I'm just wondering what upgrades are recommended? I have seen kickstart 3.1 being mentioned. I don't need much more than I've already got, as I just use it for a few games. But it would be nice to make it as good as I could!
I don't have any skills in soldering chips onto motherboards, but have seen there is space for another 512K on the board.
If it's worth adding these chips, where can I find some, and what will it actually do?
Thanks!
-
I'd add an HD.
-
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! :D
-
Another option for the RAM expansion is the kipper2 design. Fits between the socket and the cpu.
You can also snag an CFIDE68K for the hard drive/CF card/microdrive expansion.
Of course if you add both of those, the cpu is going to be sticking up pretty high! Upper half of the RF shield is definitely going to be tossed!
Of course, most A500's don't know what the top of their cases feel like anyway as they're usually opened so the owner can tinker.
Curtis
-
http://kipper2k.com/amigaforsale/
Check here for some new products for your Amiga 500 :)
Maybe 4/8 mb Ram..
-
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! :D
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
-
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! :)
-
Just don't let Mike replace your Agnus and you should be okay. :P
-
Just don't let Mike replace your Agnus and you should be okay. :P
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! :)
-
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! :)
She's still working Mike that's the main thing...!
-
Wow, thanks for everyone's fast responses!
Haha, watch out, it's a money pit! ;)
I will try not spend too much at once Mike!!
I do already have an external floppy, so I'm on the way! Lots there I don't understand yet, so will start researching right away. I've got a Rev 6A board, and GadgetUK told me it already has a better Agnus than earlier ones. I'm a total novice when it comes to anything electronic, but enjoying learning about my Amiga!!
What I've got to do now is somehow find out why my comp pro joystick has stopped turning left! I have taken it apart and tried to test the switches for continuity, but not quite sure if that is what I should be doing? Need to find at least one more in any case.
Thanks again, if it's ok to ask a question or two anytime, I'll be very grateful!
-
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)
-
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! ;-)
-
Indeed it is an 8372A!
I'll have a look into soldering on those pads. When you say more graphically intense, do you mean that even for games I'm familiar with, the graphics will look better? Or for other things I might do on the Amiga?
I doubt I'll be doing anything like you, no way I will understand programming!
-
Would WD40 be good as a contact cleaner? Stupid question I know...:)
-
Would WD40 be good as a contact cleaner? Stupid question I know...:)
Yes! That's fine for joystick microswitches. What make is it?
Personally I would do the 1Mb chipram mod, thats easy. Then add a 4 or 8 Mb board from kipper2k. If you are going to get a HDD (which can be hard to find for a 500) then definitely get the 8Mb board, if you are just going to stick with floppies then 4Mb is all you need, and infact is probably an overkill - that said price difference is hardly anything so I would stick 8Mb in.
If you do get a HDD, then and only then, consider getting 3.1 ROM and a ROM switcher, and if you want to be able to press a key to quit in whdload (software that runs games from HDD) you might want that 68010, I wouldnt bother tbh as you wont be running at stock speed.
You can make that 1Mb chip RAM toggleable with a switch btw, if you dont permenantly want 1Mb chip ram.
ECS denise isnt really needed unless you want to play ECS games, which I think need kickstart 2+ (eg 3.1), so not much point in doing that chip unless you get HDD and 3.1 kickstart etc.
External floppy is a good idea, try to get a cumana - those thing run forever. If you need a new joystick, look for a good cruiser or zipstick. I prefer the cruiser myself as its easier to hold but zipstick tend to be more robust.
I would add more RAM to those empty sockets youve got then you would have 1.5Mb chip ram, but it would require soldering many pins. If you explore that idea make sure to get sockets and solder the sockets in place and not chips - stick the chips in the sockets. Getting those RAM chips could be tricky - try EBAY or aminet. I saw a cut off board section just last week that had those RAM chips on it, but they needed desoldering first.
I would be interested to know the model of the RAM on your board, the older revs like mine have 41256, or 51258, 81256 etc. And there are normally 16 of them, I think yours has 8 and 8 empty spaces?
-
Oh oh oh!!!! Before I forget!!! THE upgrade you MUST get in my mind is a HxC Floppy Emulator from Lotharek (google that name). It replaces your FDD with an SD slot, stick a 2gb SD card in for £4 with hundreds of games and you are away. For a 500 its easier than the HDD route imo. They cost around £60 ish but well worth it. There are different models, some with LCD and buttons etc. To get the best result you need to be handy with DIY but you can avoid fitting an LCD etc, its up to you how you mount the thing.
Heres the drive in my ST:-
See this thread for how I did this, and earlier up the thread is a pic of an amiga with an external unit:-
http://atariage.com/forums/topic/208925-hxc-floppy-emulator-where-to-mount-the-lcd/
(http://www.c5software.co.uk/atarist/fitted.jpg)
-
Yes! That's fine for joystick microswitches. What make is it?
Personally I would do the 1Mb chipram mod, thats easy. Then add a 4 or 8 Mb board from kipper2k. If you are going to get a HDD (which can be hard to find for a 500) then definitely get the 8Mb board, if you are just going to stick with floppies then 4Mb is all you need, and infact is probably an overkill - that said price difference is hardly anything so I would stick 8Mb in.
If you do get a HDD, then and only then, consider getting 3.1 ROM and a ROM switcher, and if you want to be able to press a key to quit in whdload (software that runs games from HDD) you might want that 68010, I wouldnt bother tbh as you wont be running at stock speed.
You can make that 1Mb chip RAM toggleable with a switch btw, if you dont permenantly want 1Mb chip ram.
ECS denise isnt really needed unless you want to play ECS games, which I think need kickstart 2+ (eg 3.1), so not much point in doing that chip unless you get HDD and 3.1 kickstart etc.
External floppy is a good idea, try to get a cumana - those thing run forever. If you need a new joystick, look for a good cruiser or zipstick. I prefer the cruiser myself as its easier to hold but zipstick tend to be more robust.
I would add more RAM to those empty sockets youve got then you would have 1.5Mb chip ram, but it would require soldering many pins. If you explore that idea make sure to get sockets and solder the sockets in place and not chips - stick the chips in the sockets. Getting those RAM chips could be tricky - try EBAY or aminet. I saw a cut off board section just last week that had those RAM chips on it, but they needed desoldering first.
I would be interested to know the model of the RAM on your board, the older revs like mine have 41256, or 51258, 81256 etc. And there are normally 16 of them, I think yours has 8 and 8 empty spaces?
Joystick is a comp pro, also have a quickshot that down doesn't work on. Sounds like it is also micro switched.
I'll give them a go with the WD40.
I'm ok with the few games that I have for now, they all worked fine before, but I may try to find some that I don't have anymore. But probably they would be fine with stock Amiga, with the trapdoor expansion. It would dbe great fun to add more RAM to the board though!!
The RAM is D424256C, does that sound right? There are 4 chips and 4 spaces on this board.
Here they are:
[ATTACH]2854[/ATTACH]
Would it be hard to find the chips and sockets?
-
Oh oh oh!!!! Before I forget!!! THE upgrade you MUST get in my mind is a HxC Floppy Emulator from Lotharek (google that name). It replaces your FDD with an SD slot, stick a 2gb SD card in for £4 with hundreds of games and you are away. For a 500 its easier than the HDD route imo. They cost around £60 ish but well worth it. There are different models, some with LCD and buttons etc. To get the best result you need to be handy with DIY but you can avoid fitting an LCD etc, its up to you how you mount the thing.
Heres the drive in my ST:-
See this thread for how I did this, and earlier up the thread is a pic of an amiga with an external unit:-
http://atariage.com/forums/topic/208925-hxc-floppy-emulator-where-to-mount-the-lcd/
(http://www.c5software.co.uk/atarist/fitted.jpg)
I like the sound of that! May feel a bit like a crime to cut a hole in my Amiga though!
-
Wow, thanks for everyone's fast responses!
I will try not spend too much at once Mike!!
I do already have an external floppy, so I'm on the way! Lots there I don't understand yet, so will start researching right away. I've got a Rev 6A board, and GadgetUK told me it already has a better Agnus than earlier ones. I'm a total novice when it comes to anything electronic, but enjoying learning about my Amiga!!
What I've got to do now is somehow find out why my comp pro joystick has stopped turning left! I have taken it apart and tried to test the switches for continuity, but not quite sure if that is what I should be doing? Need to find at least one more in any case.
Thanks again, if it's ok to ask a question or two anytime, I'll be very grateful!
To test continuity its easy:-
On each microswitch (take the joystick to bits so you can get at the switches), you will see 2 contacts on each switch with a wire going to each contact. Put your black wire on one contact and the red wire on the other, and put meter on continuity test or ohms. Press the switch and it should be a short circuit, or very low <= 10 ohms. Test the good switches first so you can see it going on and off correctly on your meter, then test the dodgy switch.
Some times those microswitches fail, you can salvage them from other joysticks, and I believe there are suppliers of new microswitches still depending on the size and type etc but they are pretty standard.
Same goes for the microswitches soldered onto Mice boards for left and right click, they tend to be standard and can be replaced pretty easily.
-
Joystick is a comp pro, also have a quickshot that down doesn't work on. Sounds like it is also micro switched.
I'll give them a go with the WD40.
I'm ok with the few games that I have for now, they all worked fine before, but I may try to find some that I don't have anymore. But probably they would be fine with stock Amiga, with the trapdoor expansion. It would dbe great fun to add more RAM to the board though!!
The RAM is D424256C, does that sound right? There are 4 chips and 4 spaces on this board.
Here they are:
[ATTACH]2854[/ATTACH]
Would it be hard to find the chips and sockets?
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.
-
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...
-
Get confusing readings from the joystick. I've got the multimeter set to 200 ohms, lowest setting. But when testing the good switches, don't get a constant reading when pressing the switch, might begin with 142.7 down to 0.14. But constantly changing. Strange.
Even the bad switch still give the same kind of changing readings.
Tested the fire buttons just in case. Right fire gives the same changing values, but left is completely dead, even though it's not a micro switch, just two metal contacts pushing together. They do make contact, just made sure!
-
I believe if you're going to go that route you also need to solder in the resistors? Might want to double check...
I reckon I could just about handle doing that. Well I'd give it a go...the resistors shouldn't be too hard to find?
-
Get confusing readings from the joystick. I've got the multimeter set to 200 ohms, lowest setting. But when testing the good switches, don't get a constant reading when pressing the switch, might begin with 142.7 down to 0.14. But constantly changing. Strange.
Even the bad switch still give the same kind of changing readings.
Tested the fire buttons just in case. Right fire gives the same changing values, but left is completely dead, even though it's not a micro switch, just two metal contacts pushing together. They do make contact, just made sure!
You aren't making firm enough contacts on the pins, that's all. Press hard and get someone else to move the buttons / directions etc and it will be more constant.
EDIT: If its metal contacts and they are definitely making contact then it could be the main wire. Sometimes the wire can work if you bend it certain directions, its worth trying that on the Amiga, plug it in, and hold the button or direction that's not working and bend the main wire at different points to see if it makes any difference at all.
Oh, i've just remembered - you swapped your CIA's around, if one was faulty (giving you flashing LED etc) then you could have put the duff one in the position that handles joystick input... If you dont get anywhere with the stick try swapping the stick into the mouse port and see if you can find a game that will use the mouse port and see if that's working with the stick (I suspect it will if your mouse is working), that will prove its the CIA, or you could just swap the CIA's around again and see what happens. If the stick has been working intermittantly it won't be the CIA it will be the stick btw. Ideally test another joystick in the port to rule it out but most likely problem is the buttons or the wire.
-
I reckon I could just about handle doing that. Well I'd give it a go...the resistors shouldn't be too hard to find?
Will be easy to find resistors, the really hard thing to find are the RAM chips at reasonable price. £5 is cheap really, I looked at the old 41256's for my model and they were £3 each and 16 are required for my version =O Luckily because I used to be in the industry I found 80+ of them in my IC collection =)
-
You aren't making firm enough contacts on the pins, that's all. Press hard and get someone else to move the buttons / directions etc and it will be more constant.
EDIT: If its metal contacts and they are definitely making contact then it could be the main wire. Sometimes the wire can work if you bend it certain directions, its worth trying that on the Amiga, plug it in, and hold the button or direction that's not working and bend the main wire at different points to see if it makes any difference at all.
Oh, i've just remembered - you swapped your CIA's around, if one was faulty (giving you flashing LED etc) then you could have put the duff one in the position that handles joystick input... If you dont get anywhere with the stick try swapping the stick into the mouse port and see if you can find a game that will use the mouse port and see if that's working with the stick (I suspect it will if your mouse is working), that will prove its the CIA, or you could just swap the CIA's around again and see what happens. If the stick has been working intermittantly it won't be the CIA it will be the stick btw. Ideally test another joystick in the port to rule it out but most likely problem is the buttons or the wire.
Damn! The Amiga is in bits as have been doing the retrobriting!
I'll put it together hopefully by Sunday and test the joystick ports, today's sunshine has done wonders, but there is still a bit more to do. The keys especially, casing is nearly there!
Had some help testing the switches just now, bit better readings, though some still changed no matter how hard I pressed.
Up - settled at 0.9
Down - 1.2
Left - No change, still infinity on display
Right - 0.9
Left Fire - stayed on infinity
Right Fire - 2.5
Could plug it all together now, but is it a good idea with absolutely no casing on?!
-
Will be easy to find resistors, the really hard thing to find are the RAM chips at reasonable price. £5 is cheap really, I looked at the old 41256's for my model and they were £3 each and 16 are required for my version =O Luckily because I used to be in the industry I found 80+ of them in my IC collection =)
Oh yeah, a fiver is absolutely fine! You can't buy that kind of luck!
-
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 might have missed something, but, I don't think this is a simple matter of adding more ram chips on the motherboard (even with resistors ;) ). Your Agnus addresses either 1 Meg of chip (preferred) OR 512K of chip and the trapdoor mapped as 512K of slow ram. It is my belief that any additional ram on the motherboard will have no refresh. OTOH, you could add the 2 Meg Agnus :).
The true fast ram boards mentioned earlier come with support circuitry for refresh.
Food for thought before you attempt this modification.
-
I would add more RAM to those empty sockets youve got then you would have 1.5Mb chip ram, but it would require soldering many pins.
Sorry, that is definitely not correct. You are not going to get more than 1 MB chip ram without upgrading to a 2 MB Agnus. And that is not simply finding a 2 MB Agnus an replacing the old 1 MB Agnus...
-
Sorry, that is definitely not correct. You are not going to get more than 1 MB chip ram without upgrading to a 2 MB Agnus. And that is not simply finding a 2 MB Agnus an replacing the old 1 MB Agnus...
Yes, you are correct, I had forgotten he has a 1Mb Agnus. Still worth doing to have 1Mb on board and 512Kb of fast(slow) RAM.
In addition to the chips you should probably put some decoupling caps on the there - 0.33uF (I've got some if you do decide to do it, just pay for postage you can have the caps - I got a bulk lot of 50 and i've only used 2 so far.)
-
Yes, you are correct, I had forgotten he has a 1Mb Agnus. Still worth doing to have 1Mb on board and 512Kb of fast(slow) RAM.
In addition to the chips you should probably put some decoupling caps on the there - 0.33uF (I've got some if you do decide to do it, just pay for postage you can have the caps - I got a bulk lot of 50 and i've only used 2 so far.)
The extra 512K on the board is mapped into the same address space as the 512K on the trapdoor expansion. You can not use both without doing a hack that allows you to map them to different address spaces.
-
think this will be fantastic upgrade for A500:
http://eab.abime.net/showthread.php?t=68459
-
Hi,
Thanks to everyone for their suggestions! I'm more confused now than before, mainly due to being at least 20 years behind you all in electronic experience!
I thought I was doing pretty good, when I put the trapdoor expansion in in 1990! Haven't done anything with computers since...
I will look up as many of your suggestions as my brain can handle, and definitely do some of them. I'd better start with the ones that don't require any soldering on the motherboard. I'd better keep it simple, I quite like using the floppies still, for the proper retro feel. But having a different drive with tons of games on it does appeal!
I'm just happy to be using my beloved Amiga again!
Thanks!