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Any Amiga fans around here? — Parallax Forums

Any Amiga fans around here?

cbmeekscbmeeks Posts: 634
in General Discussion
For those that don't know, I am a huge "vintage" computer / game console collector. I have around 60+ vintage computers and 30+ consoles.

I just landed me my first Amiga 1000. I'm a huge Amiga fan, BTW. This makes my sixth Amiga (500, 500, 600, 1200, 2000 too).

I'm itching to integrate a micro-controller (Propeller, hopefully) with it. Maybe as some storage medium. Might need an FPGA for that.

Anyway, just looking for any other Amiga fans out there. :-)
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Comments

  • kwinnkwinn Posts: 8,697
    The Prop should be able to interface an sd card to emulate tape, floppy, or a hard disk for the Amiga without having to use an FPGA.

    I haven't done this myself since I don't have much interest in vintage computers, but I did help a friend a bit as he built tape and floppy emulators for a couple of his systems using the propeller. As far as I recall the propeller chip handled all the interfacing.
  • cbmeekscbmeeks Posts: 634
    That's what I was thinking too. I remember some people over at Lemon64 (Commodore 64 forum) were saying that no way could a micro-controller reproduce a C64 floppy drive (1541). Which is true because the 1541 has a 6502 built into it.

    However, it could emulate the functionality and protocols. But pretty minimally.

    I was thinking the same thing could be done for the Amiga. But maybe even easier because the floppy drives (IIRC) aren't very advanced. Similar to the floppies of early Macs or PC's.
  • David BetzDavid Betz Posts: 14,516
    cbmeeks wrote: »
    That's what I was thinking too. I remember some people over at Lemon64 (Commodore 64 forum) were saying that no way could a micro-controller reproduce a C64 floppy drive (1541). Which is true because the 1541 has a 6502 built into it.

    However, it could emulate the functionality and protocols. But pretty minimally.

    I was thinking the same thing could be done for the Amiga. But maybe even easier because the floppy drives (IIRC) aren't very advanced. Similar to the floppies of early Macs or PC's.
    That statement makes no sense to me. Doesn't the 1541 just use a serial interface? Anything that can implement that serial protocol can emulate a 1541 drive, no? Doesn't have to be a 6502. However, even if you do want a 6502 for some reason, that could probably be emulated on the Propeller I guess.

  • cbmeekscbmeeks Posts: 634
    Maybe I wasn't clear.

    The consensus is that because the 1541 has a 6502 in it, and is much more advanced than a simple serial stream, it would be difficult at best to 100% reproduce it. Because you would have to reproduce the 6502 and all of the glue logic inside the 1541 to get a cycle accurate emulation.

    However, because the actual protocol for the C64 disk/serial bus isn't all that advanced a microcontroller could (and has) easily emulate the protocol.

    But, certain things haven't been emulated in a microcontroller that I know of. Such as the compression/fast loaders. Those rely on the 6502 INSIDE the 1541 drive to perform compression, etc.

    It probably could be done. But the gist is that a micro-controller cannot 100% emulate a CPU like the 6502 along with all of the other circuitry inside the 1541.

    That's all I meant.
  • David BetzDavid Betz Posts: 14,516
    cbmeeks wrote: »
    Maybe I wasn't clear.

    The consensus is that because the 1541 has a 6502 in it, and is much more advanced than a simple serial stream, it would be difficult at best to 100% reproduce it. Because you would have to reproduce the 6502 and all of the glue logic inside the 1541 to get a cycle accurate emulation.

    However, because the actual protocol for the C64 disk/serial bus isn't all that advanced a microcontroller could (and has) easily emulate the protocol.

    But, certain things haven't been emulated in a microcontroller that I know of. Such as the compression/fast loaders. Those rely on the 6502 INSIDE the 1541 drive to perform compression, etc.

    It probably could be done. But the gist is that a micro-controller cannot 100% emulate a CPU like the 6502 along with all of the other circuitry inside the 1541.

    That's all I meant.
    That's interesting. Are you saying that the 1541 protocol allows 6502 code to be downloaded into the drive and run on the 6502 in the drive? That's pretty cool.

  • cbmeekscbmeeks Posts: 634
    Yeah, exactly. In fact Woz got all kinds of accolades because the floppy drive for the Apple II was so simple. Most of the logic was handled in the main CPU of the computer.

    But the 1541 contained a complete computer inside running a 6502. Some software could actually pass code into the drive to get a poor man's multi-core system.

    However, due to Tramiel being so stingy, the serial bus on the C64 was severely crippled causing the 1541 to operate much slower than it could. The 1541 was pretty advanced for its day.
  • kwinnkwinn Posts: 8,697
    @cbmeeks

    I would be very surprised if the propeller could not emulate all the functions of the 1541 and floppy drive using an sd card, and probably much faster as well. I'm not saying that it would be a simple project, but the propeller has way more processing power than the 6502. Do you have a schematic or better yet, a manual for the 1541 controller?
  • David BetzDavid Betz Posts: 14,516
    kwinn wrote: »
    @cbmeeks

    I would be very surprised if the propeller could not emulate all the functions of the 1541 and floppy drive using an sd card, and probably much faster as well. I'm not saying that it would be a simple project, but the propeller has way more processing power than the 6502. Do you have a schematic or better yet, a manual for the 1541 controller?
    I think the problem is that one of the "features" of the 1541 is running arbitrary 6502 that gets downloaded over the serial connection. To do that requires a full emulation of the 6502 and the 1541 hardware registers. I would assume that a 6502 emulator is within the capability of the Propeller but I'm not sure anyone has done one yet. And the emulator would have to be cycle-accurate if any of the downloaded 6502 is going to be doing any bit banging.

  • cbmeekscbmeeks Posts: 634
    @DavidBetz

    That is correct. :-)

    Anyway, it's been done "good enough" for some cases. Arduino's can emulate the protocol but they are missing fast loaders, etc.

    For the Amiga, I'd be interested in seeing a floppy emulator. Most implementations use FPGA I would imagine.

  • potatoheadpotatohead Posts: 10,261
    edited 2015-12-15 20:51
    We have a lot of a 6502 in an NES emulation someone did on P1. I should go and find it again...

    It is missing decimal mode, and I am not sure it is cycle exact. Cycle exact is needed for disk I/O routines. Emulation of this is tough. Hardware 1451 simulators exist, but remain imperfect last I checked.

    The ability to run code on the drive was used to make fast loaders and copy protection, among other things.

    Re:Amiga

    I'm a fan, but I stepped away from 16 bit computing, and did not use many machines from that era enough to be familiar like I am with most 8 bit machines. Instead, I was doing manufacturing related computing on the DOS PC and later on, modeling / engineering on SGI IRIX.

    So, SGI is my "Amiga" type machine.

    And it's a bit much for hobby nostalga. 8 bits is enough for that.

    Great computers though. I am frequently tempted to set one up to better understand what I missed!

    Eric Ball also made a 6502 core in Spin. At one point, we were thinking of doing some emulation on the P1, but never got past building a few basic pieces. Additionally, a lot of 6502 machines do require cycle exact, and speed to do a reasonable job.
  • kwinnkwinn Posts: 8,697
    edited 2015-12-15 20:53
    David Betz wrote: »
    kwinn wrote: »
    @cbmeeks

    I would be very surprised if the propeller could not emulate all the functions of the 1541 and floppy drive using an sd card, and probably much faster as well. I'm not saying that it would be a simple project, but the propeller has way more processing power than the 6502. Do you have a schematic or better yet, a manual for the 1541 controller?
    I think the problem is that one of the "features" of the 1541 is running arbitrary 6502 that gets downloaded over the serial connection. To do that requires a full emulation of the 6502 and the 1541 hardware registers. I would assume that a 6502 emulator is within the capability of the Propeller but I'm not sure anyone has done one yet. And the emulator would have to be cycle-accurate if any of the downloaded 6502 is going to be doing any bit banging.

    Perhaps so, but after reading about the 1541 on wikipedia (https://en.wikipedia.org/wiki/Commodore_1541) why would you want to fully emulate it. Better to create an sd interface that is compatible with the C64 and actually works reliably and at reasonable speeds.
  • cbmeekscbmeeks Posts: 634
    You would want to emulate it in order to run copy protected disk images. Not all images have been converted to non-copy protected images.

    And you would also want to emulate it in order to use fast loaders.

  • evanhevanh Posts: 15,910
    I've still got an A3000 that's probably dead now.
  • cbmeekscbmeeks Posts: 634
    @evanh

    Want to sell it? :-D

  • kwinnkwinn Posts: 8,697
    cbmeeks wrote: »
    You would want to emulate it in order to run copy protected disk images. Not all images have been converted to non-copy protected images.

    And you would also want to emulate it in order to use fast loaders.

    Ah, that makes sense. In that case one may want to use a 6502 for for that part of the interface and leave the rest of the bit banging to the prop.
  • evanhevanh Posts: 15,910
    cbmeeks wrote: »
    Want to sell it? :-D

    Hmm, dunno, I had wondered if I'd ever find a SCSI-I to SATA adaptor and be able to put something bigger and quieter on the old girl. It's got a horribly noisy 1GB drive from back when PC's were limited to 800MB by the ancient CHS parameters. A friend tried an IDE to SATA adaptor on his A1200 but those adaptors don't understand pre-ATA data so are a dead-end.

    Have you pursued anything alone those lines?
  • cbmeekscbmeeks Posts: 634
    Unfortunately, no.

    I have ways of getting software on my 8 bit machines but I haven't tried with my 16 bit machines.

    I'm hoping to change that. Especially with my Amiga 1000 I just bought. There is something about that machine that I really enjoy. Maybe because it was the first.

    I just need to see if I can repair it. All I get on power up is a blank, green screen. Which means, IIRC, the Agnus chip is bad or not firmly in its socket.

    Hopefully this weekend I can tear it down some more and re-socket all the chips.

    Oh, and if you ever decide to sell that Amiga, I'd be a happy buyer. :-D

  • Bill HenningBill Henning Posts: 6,445
    Me too...

    I had one of the first Amiga 1000's in Vancouver.

    The Amiga 1000 was the inspiration in my designing Morpheus, as I figured that with two Props and 512KB-8MB of SRAM I should be able to emulate an Amiga.

    Life intruded, and I never even started that emulator.
    cbmeeks wrote: »
    For those that don't know, I am a huge "vintage" computer / game console collector. I have around 60+ vintage computers and 30+ consoles.

    I just landed me my first Amiga 1000. I'm a huge Amiga fan, BTW. This makes my sixth Amiga (500, 500, 600, 1200, 2000 too).

    I'm itching to integrate a micro-controller (Propeller, hopefully) with it. Maybe as some storage medium. Might need an FPGA for that.

    Anyway, just looking for any other Amiga fans out there. :-)

  • evanhevanh Posts: 15,910
    It's funny how the 68k got branded 16-bit yet was only ever 32-bit capable. I guess that's how arrogant the PC has always been. They can't be seen as out of date so they make Smile up.
  • msrobotsmsrobots Posts: 3,709
    Yeah, I really liked the 68k assembler. How simple and easy compared to 86xx with all them segment pointers.
    Just flat memory space. Quite orthogonal command set. Real fun to program.

    Of course I never had a Amiga. I had the Atari ones.

    Enjoy!

    Mike
  • cbmeekscbmeeks Posts: 634
    Bad news on my Amiga 1000.

    All I can get is a solid green screen at power up. I've done a little research and it appears it's because of bad chip RAM. Which isn't the easiest (or cheapest) thing to have to replace.

    Ugh.

    Oh well, maybe one day I will track more down and see if I can get it running.
  • kwinnkwinn Posts: 8,697
    cbmeeks wrote: »
    Bad news on my Amiga 1000.

    All I can get is a solid green screen at power up. I've done a little research and it appears it's because of bad chip RAM. Which isn't the easiest (or cheapest) thing to have to replace.

    Ugh.

    Oh well, maybe one day I will track more down and see if I can get it running.

    What is the part number of the ram chip. I have some oldies left in my old parts box. Perhaps one of them would work for you.
  • cbmeekscbmeeks Posts: 634
    I'm not sure at the moment. I will get the board back out and take a look.

    Thanks very much!

  • evanhevanh Posts: 15,910
    I've also got an even older A2000 (Known to have mice living in it when it was on a farm a long time ago) with 2MB fitted on an 8MB expansion board. Those DRAMs are probably the right sort. I can't remember if they were socketed though. Will try to dig it out of the pile of junk in the garage ...

    International freight will be a bit of cost if you want the whole A2000.
  • Heater.Heater. Posts: 21,230
    I'm surprised that suspicion is cast on the Amiga RAMs when the machine fails.

    I would expect the semiconductors, RAMs and such, to stand the test of time very well.

    I would be very wary of the electrolytic capacitors and other components after all these years.

  • cbmeekscbmeeks Posts: 634
    @evanh

    Thanks for the offer! I sent you a PM.

    @Heater
    The only reason I say the chip RAM is because that's what various websites have said based on the symptoms my Amiga displays.

    When I power it on, it is a solid, dark green screen. A few seconds later it changes the green to a very bright green. But that's it.

    The capacitors look good with just basic visual inspection. I have tons of pictures of the board if anyone is interested.

    I asked on Lemon Amiga but no one has responded yet. Not sure where else to ask. :-)

    Thanks!
  • kwinnkwinn Posts: 8,697
    Heater has a valid point. It is possible the electrolytic capacitors have dried out after sitting for a long time without power on them. If you have a scope take a look at the power rails near the capacitors or nearby chips. If there is noise there they need to be replaced.

    When I refurbish or resurrect old equipment for customers I make a point of replacing all of the electrolytic capacitors. Much easier than trying to hunt down one or two bad ones.
  • kwinnkwinn Posts: 8,697
    PS - Of course it is possible the ram or some other portion of the circuitry could be bad, but power supply is probably the best place to start troubleshooting. Bad power can produce a lot of strange and varied symptoms.
  • cbmeekscbmeeks Posts: 634
    @kwin

    Thanks for the tip! I will do that.

    My debugging skills are a million miles from professional.

    I do have an oscilloscope. So, I assume I would just put GND probe on (obviously) the GND pin of the cap and the signal to the other side?

    What would a "clean" working cap look like on the scope?

    Thanks!

  • Heater.Heater. Posts: 21,230
    edited 2015-12-22 16:19
    Well all this cap suspicion is just wild guessing of course. However caps are notoriously the most unreliable and short lived parts of systems.

    Connectors are of course even more unreliable, what with corrosion and mechanical jiggling.

    I would not discount RAM chip failure but silicon tends to live a long time unless it's abused.

    Anyway, rule number one is check your voltages. Are all the pwer supplies delivering what they should? Is ground actually ground?

    Then we can think about using the scope.

    Yep, ground to ground, signal to power rail.

    What we are looking for is any weird noise, spikes and dips, going appearing on the power rail. Look directly on the power pins of the chips.

    My experience of this is that power rails often look horrible. It's a question of how how horrible they are,

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