EEVBlog #438 - Amiga 500 Retro Computer Teardown - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: March 13, 2013, 10:16:39 am
content: Vintage Teardown Tuesday.What's inside the 1987 Commodore Amiga 500 computer.Dave.

author: JoannaK
author_rank: Frequent Contributor
timestamp: March 13, 2013, 10:28:37 am
content: Looks oddly familiar.. Like the A500 I used to own back then.For the record, under the Rock-lobster text, there are initials of A500 designers.For Amiga ASIC:s you'd need to check info of Jay Miner, since he did the design essentially on his own.http://en.wikipedia.org/wiki/Jay_MinerThere are so much memories, so much info .. A lot most likely forgotten by now.

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: March 13, 2013, 10:46:20 am
content: Cool, gotta love old stuff for still working (mostly) after all these years. Yet a newer monitor can't even keep it's backlight working.One thing you might want to check on the floppy drives though, if they're belt-driven, that the belts haven't rotted away... It's a common thing for old floppy-based systems.

author: moemoe
author_rank: Regular Contributor
timestamp: March 13, 2013, 10:54:29 am
content: Some months ago I disassembled one of these myself, because I had to fix an issue. Luckily with enough googling I could get copies of all third party expansions' datasheets/manuals."Sixteen of these Chips to get 512MB" – I think you probably ment Kilobytes @7m25And your Amiga is lucky, many of them have lost their knobs to eject the floppy.Btw, schematics are available athttp://project64.c64.org/hw/amiga.htm

author: JoannaK
author_rank: Frequent Contributor
timestamp: March 13, 2013, 11:22:49 am
content: Quote from: justanothercanuck on March 13, 2013, 10:46:20 amI think most of the 3.5" drives were made with direct drive motors. Larger ones were usually were belt driven (like 1541).I wonder though IF I should sell my A1000 and Apple 2e, most likely no-one willing to pay anythign out of those (assuming they still work).

author: Nack486
author_rank: Contributor
timestamp: March 13, 2013, 11:55:26 am
content: Those vintage computers are awesome! I'd love to get my hands on something from the eighties, even if it's a Pravetz (local Apple clone).I bought a couple of 6800 clones made here in Bulgaria and this video made me enthusiased again about making something with them.

author: sleemanj
author_rank: Super Contributor
timestamp: March 13, 2013, 12:10:03 pm
content: *sniff* /me wipes away tearOwned, used, repaired (and destroyed) many Amigas in my mis-spent youth. A500s, 2000s, 500+'s, 600's, 3000s, and a couple of 1000's (and of course C64s, 128s and even a 128D at one time).The heavy shielding on the "Fast Ram" expansion was I think really because it was sold as an optional extra and thus installed by hamfisted people who wouldn't take notice of static precautions.The expansion port on the left was used mainly for Hard Drives, CD-Rom Drives (somewhat later), and most amazingly what were called Bridgecards ("Sidecar") basically what was needed to turn your Amiga into a cross-breed of an MS-DOS running PC "inside" an Amiga, really whizzy bit of kit not too far removed in idea from VMWare and modern virtualisation/emulation, except mostly done in hardware.Taking apart your Amiga (500 especially) wasn't unusual at some point as upgrading the "Kickstart" ROM (or installing a "Kickswitch" and having both an old 1.x and 2.x series rom installed and switchable between the two) was basically a right a passage at least around here, I doubt there are too many 500's around with intact warranty seals.Sold off all my remaining Amiga a few months back for a song just to get rid of it, have kept an old dead A3000 and an A600, which one day (when I find that Round Tuit) I intend to transplant modern hardware into the cases.NB: If you come across a 1000, the case lids have signatures of the people responsible embossed on the underside.

author: dgarlans
author_rank: Newbie
timestamp: March 13, 2013, 02:06:25 pm
content: Ahh the A500... a good friend of mine from Finland gave me his and I brought it back home to the US, and ran into a serious problem with the output being either PAL, or an RGB format that I couldn't plug into anything.I had the same problem with the Atari ST he gave me too. Now they're collecting dust in my closet

author: nharrer
author_rank: Contributor
timestamp: March 13, 2013, 02:12:51 pm
content: Wow, that was wonderful. Thanks Dave, that made my day.So much nostalgia. Sigh.... And yeah, it's pretty painful to look at the crappy software compared to what we are used to nowadays. Best kept in memory.BTW. The Guru Meditation is pretty much what the BSOD is for windows. It means the system crashed seriously. The numbers tell you something about what happened.I looked up the error code. 81000005 stands for corrupted memory list. I guess the system ran out of memory. The OS (the Workbench) uses up a lot of memory. So games where usually designed to boot straight from the disk without using the OS at all. The system rebooted after you pressed the mouse button at the Guru Meditation screen. Since you had the game disk already in the drive. It loaded again. This time without the Workbench hogging up the memory, and it worked.I wrote my first programs on an Amiga 500. Mostly assembly stuff. Ohh. I saw that Guru Meditation screen so many times...

author: Skimask
author_rank: Super Contributor
timestamp: March 13, 2013, 02:20:24 pm
content: My 1084S JUST blew up a few weeks ago! More specifically a cap somewhere in there committed suicide. Much as I'd like to fix it...not worth it.Sad day. At least the old '500 is still running just fine.

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: March 13, 2013, 02:50:23 pm
content: Quote from: sleemanj on March 13, 2013, 12:10:03 pmCan't say I'm happy about hearing that, but to each their own...

author: baoshi
author_rank: Regular Contributor
timestamp: March 13, 2013, 03:18:54 pm
content: The solder mask looks like printed using silkscreen process hence the bumpy grids.

author: Winston
author_rank: Regular Contributor
timestamp: March 13, 2013, 03:25:48 pm
content: Quote from: JoannaK on March 13, 2013, 10:28:37 amJay was a really talented guy with chip design. A three-part series of articles about the Atari 400/800 chipset, very advanced for their time, in Byte magazine got me interested in Atari machines. Jay left Atari and designed the brilliant Amiga chipset. For a while, his company tried to fund development by selling a line of joysticks. When Jack Tramiel left Commodore (IIRC because they refused to hire his son onto their board of directors) and bought Atari, Commodore bought Amiga. Many engineers left Commodore with Tramiel, so the Atari 520ST and 1040ST line could be said to be a Commodore (engineer) designed machine while the Commodore Amiga could be said to be an Atari (engineer) designed machine.

author: obsoletemac
author_rank: Newbie
timestamp: March 13, 2013, 04:32:27 pm
content: For a good read about commodore, check out "On the edge" (http://www.amazon.co.uk/The-Story-Commodore-Company-Edge/dp/0973864907)//c

author: andersm
author_rank: Super Contributor
timestamp: March 13, 2013, 04:39:30 pm
content: Quote from: obsoletemac on March 13, 2013, 04:32:27 pmBe sure to get the second edition though, it contains some extra material. Thesequel, which deals specifically with the Amiga era, is due out later this year.

author: Kaluriel
author_rank: Contributor
timestamp: March 13, 2013, 04:55:07 pm
content: I love the graphical style of Amiga games, I'm tempted to get out my old Commadore 64 now, dust it off and play Ghostbusters

author: John Larsen
author_rank: Newbie
timestamp: March 13, 2013, 05:10:58 pm
content: THE computer where I learned to program assembler and C.I had the memory expandtion in trapdoor and CPV SCSI 120 MB HD in (sidecar) expandtion .... uhhhhh sexy

author: Ferroto
author_rank: Frequent Contributor
timestamp: March 13, 2013, 06:52:04 pm
content: That 4256 is a couple of months older then me. I was born in the last week of '87. I remember learning to code on a commodore 64 man that brings back memories.

author: jaycee
author_rank: Regular Contributor
timestamp: March 13, 2013, 07:01:05 pm
content: Ah, good old Amiga... what can I say about these, best computer EVER and if Commodore hadn't majorly screwed up, would probably still be around!Firstly, before Commodore owned the company, the designers were working in Silicon Valley and wanted to be able to talk about the development in bars etc, but without being overheard by possible competitors. So they named things after girls ! The A1000 was called "Lorraine", and then we had the chips Agnus, Denise, Paula etc. Amiga is apparently Spanish for "Female friend".The hybrid is effectively a triple 4-bit R2R video DAC. Presumably the reason the hybrid was used, was to get accurate matching of the resistors. In the later A600 machine, which uses SMD parts, they did away with this and just used 1% SMD resistors. For those of you interested, I've attached a snippet of the schematic which shows what the hybrid would've contained.

author: Plecharts
author_rank: Contributor
timestamp: March 13, 2013, 07:28:55 pm
content: I think I saw a bodgewire at 24 minutes and 50 seconds, check out the crystal's right side, probably a wire that is soldered to the crystal and to the trace right next to it.Code:https://www.youtube.com/watch?v=HKNVIgsbYrA&t=24m50sEDIT: The forum doesn't like linking in the exact time in the YT URL...

author: jaycee
author_rank: Regular Contributor
timestamp: March 13, 2013, 07:38:22 pm
content: Oh, the hybrid also contained some RGB+Sync -> Composite circuitry. I'm not sure why it was only mono. Pretty much all A500's came with an external "video modulator" that plugged into the Video port, and converted the RGB output into RF for a television, and also colour Composite. In the later Amigas, this stuff was implemented using a Sony CXA1145 video encoder, as many games consoles of the time also did.Technically thats not a bodge wire - just ensuring that the case of the oscillator is connected to shield ground.

author: Plecharts
author_rank: Contributor
timestamp: March 13, 2013, 08:25:33 pm
content: Quote from: jaycee on March 13, 2013, 07:38:22 pmPlease explain why it would need to be connected to ground, I don't see any reason why the crystal wouldn't work without it.

author: jaycee
author_rank: Regular Contributor
timestamp: March 13, 2013, 08:31:15 pm
content: Just for shielding purposes, a bit overkill since as the entire PCB is inside a screening cage anyway. Maybe this is only something they did on the early runs, I have never seen this on A500+ or later models.

author: Big_Al
author_rank: Contributor
timestamp: March 13, 2013, 09:21:21 pm
content: I remember first seeing the Amiga 500 on a TV show back in about 1985-ish I think it was.It was absolutely stunning at the time. They had it playing some sort of orchestral type audio sample, and compared to the rubbish sound of all the other computers of the time it was amazing.I instantly wanted one but couldn't afford one as I was only about 15.I eventually brought one in 1991 and loved it.As lots of other people I also learned how to program in 'C' on it, the best language ever as far as I'm concerned.From what I believe, the 68000 proc was designed around the C language.Nice one Dave.

author: MartinX
author_rank: Regular Contributor
timestamp: March 13, 2013, 09:34:57 pm
content: Start it up again and this time connect it to some speakers, lets hear the sound from that game! As Big_Al said the sound was one of the main selling points of this machine, most other computers of the day could just manage some blip-blop sounds.

author: Mike Warren
author_rank: Unknown
timestamp: March 13, 2013, 11:41:19 pm
content: That was a nice bit of nostalgia. I finally chucked my last 2 A500s and one A590 hard drive in the bin about 6 months ago.

author: AlfBaz
author_rank: Super Contributor
timestamp: March 14, 2013, 03:16:43 am
content: Here in australia Keno was run on an amiga for years.Commodore stuffed up by not monopolising on there CD32 console. I think it was only a year or two after its release that sony released the play station and pretty much took over the world...I remember seeing the CD32 demoing in shops with signs underneath it saying "this is not a video"... The first lifelike photo I ever saw on a PC was a photo of a ladies face on the Amiga 1200, it came on a floppy with a magazine. I ran out and called the entire family in to see this amazing wonder

author: pbendel
author_rank: Contributor
timestamp: March 14, 2013, 04:16:05 am
content: Nice machines. I noticed the second machine had an expansion card in it with a toggle switch. Perhaps that was a kickstart ROM?

author: gnif
author_rank: Unknown
timestamp: March 14, 2013, 04:22:05 am
content: That is a common LCD fault, the mosfets driving the inverters often fail, and the circut protects itself and shuts down he back lighting when it detects over current. Just replace the drivers and it will work again

author: sleemanj
author_rank: Super Contributor
timestamp: March 14, 2013, 06:06:41 am
content: Quote from: pbendel on March 14, 2013, 04:16:05 amThe Kickstart ROM is the Commodore branded chip next to the CPU, the "kickswitch" devices plugged into that socket after removing the ROM (either directly or some had an IDC cable), and you plugged two Kickstart ROM chips into that board (your original and the new one). Some werecontrolled by a physical switch, andsome had a couple of extra flying wiresonto a couple of pins of some other chips and was triggered off of key hold at bootup, from memory.The second machine's expansion board is just a third party RAM expansion (as far as I remember, the trapdoor was only ever used for RAM & RTC expansion), the switch will be simply to enable/disable the ram expansion (back compatibility basically).

author: JoannaK
author_rank: Frequent Contributor
timestamp: March 14, 2013, 12:07:47 pm
content: Quote from: sleemanj on March 14, 2013, 06:06:41 amYes.. Some old programs were coded in a (wrong) way that extra memory cause them crash. So to be comptible with lame coding, you had to have switch option. I even added similar switch to my own 512K memory expansion.And that expansion is smaller cause it uses newer 256k*4bit Dram chips instead those 256k*1 that original Amiga has.Some things Dave forget to mention ... Amiga was the *first* home computer with build.in multitasking, good colors (and the pcm sound). Comparable quality Macs and Pc-clones were years away.It retrorespect it was kinda sad that Amiga was declared to be *toy* since it had those multimedia-capabilities inbuild.

author: Dazza
author_rank: Newbie
timestamp: March 14, 2013, 01:14:51 pm
content: Awesome blast from the pastI used to be Technical Editor of Amiga Computing magazine, a UK publication, back in the day and we were always tearing down new kit when it arrived for review. Loved it.Dave's tear-down has now given me the urge to dig out my old Amiga A1200 and my two Atari 800's. The A1200 is in good working order but one of the Atari's doesn't power up and the other has a problem with one of the ports. Might try my hand at scavenging parts from one to get the other up and running.Thanks Dave

author: iva
author_rank: Contributor
timestamp: March 14, 2013, 08:22:10 pm
content: Quote from: sleemanj on March 13, 2013, 12:10:03 pmHmm, I think that *mainly* it was to used to plug-in cards like the ActionReplay to hack/crack games at will, I had an Mk.I and an Mk.IIIhttp://amiga.resource.cx/exp/actionreplayPS I registered and presented myself 3 years ago and it took the Amiga teardown to give me the will to post a second time, ah the power of those memories!

author: JoeMuc2013
author_rank: Contributor
timestamp: March 15, 2013, 07:32:17 am
content: Hi Folks,thanks Dave, that brought back nice memories indeed.The expansion port could also be used to turn the A500 into something similar to an A2000. Look what this beast can do:http://www.amiga-hardware.com/showhardware.cgi?HARDID=1369.That put an end to the A500's portability but who cares? It was pretty cool and maximum geekPlus, A2000 hardware was often much cheaper than the A500 equivalent because manufacturers needed to add a case and a power supply for most A500 extensions.The RAM expansion bus could also be used for different purposes than just expanding the RAM and adding a battery backed up clock. There were some PC emulator boards for it, too:http://www.amiga-hardware.com/showhardware.cgi?HARDID=334The creativity these days was just amazing...Thanks again, keep up the good work!

author: RichardSim
author_rank: Newbie
timestamp: March 15, 2013, 11:27:44 pm
content: From the video @ ~38:45:QuoteHe's STILL at it. No longer (currently) directly working on games, but at NVIDIA on some of their third party libraries for games. He's pretty much legendary.

author: DimBulb
author_rank: Newbie
timestamp: March 18, 2013, 05:23:18 am
content: Thanks Dave for the great trip down memory lane. I spent a fortune (it seemed) on Amiga's back in the late 80's. Multi tasking. What a hoot.

author: AxelDominatoR
author_rank: Newbie
timestamp: March 19, 2013, 01:30:12 am
content: My first computer! NostalgyI had an A500 with RAM expansion (1MB) and an A590 external hard drive: 20 MEGAbytes!If things went differently, Amiga could still be here today. It was an awesome machine under every aspect.I still have all my disk images here on my pc with UAE!

author: KeithBrown
author_rank: Contributor
timestamp: March 19, 2013, 01:30:58 pm
content: Thanks, Dave. I'm an Amiga fan, I still have 4 of them...I actually use an A3000 to control my IR reflow toaster oven!The Rock Lobster references have caused me to have the tune running through my head since I saw your video!So for all the younger listeners, here it is:(purported to be the official music video, but the quality is poor)And a fantastic electro-mechanical rendition atSo now we all can share the brain sludge!

author: Thermal Runaway
author_rank: Contributor
timestamp: March 20, 2013, 08:48:32 pm
content: Commodore actually purchased MOS Technology, hence why lots of the chips in the Amiga were made by them. Commodore basically had their very own chip FAB, which as you can imagine was a major advantage for them at the time!Some people might recognise the name Chuck Peddle? Cool name I know. This guy worked at MOS Technology and then, after the Commodore buy-out, he became a prominent figure in Commodore computers. I think he mainly did the PET stuff though - I don't think he was still around by the Amiga era.BH.

author: Thermal Runaway
author_rank: Contributor
timestamp: March 21, 2013, 10:12:48 pm
content: Inspired by Dave's successful power-on and boot of a 25 year old Amiga 500, I decided to pull my old beauty down from the attic and give her a try as well. Unfortunately my attempts were met with a blinking power LED and cycling resets. Removing the cover revealed the obvious culprit:And...Also, bizarrely, the battery fuelled corrosion seems to have reached all the way over to FAT AGNUS!Time to get the toothbrush out!...an old toothbrush, that is

author: John Larsen
author_rank: Newbie
timestamp: March 24, 2013, 04:25:17 pm
content: Quote from: Thermal Runaway on March 21, 2013, 10:12:48 pm

author: amigo
author_rank: Regular Contributor
timestamp: March 24, 2013, 05:26:46 pm
content: Suffice to say I was a big Amiga fan (I still think it was way ahead of its time) and this did bring a tear to my eye. Not to mention I yelled at Dave (across the screen) a few time while watching the video.<----- Just look at my handle, long ago my (at the time) coworkers gave this nickname to me because I used to bring my Amiga to work, and it stuck all these years...Thanks for the video, Dave.

author: Markybhoy
author_rank: Regular Contributor
timestamp: March 27, 2013, 08:39:47 pm
content: A recent issue of Retro Gamer Magazine was dedicated to the A500

author: gnif
author_rank: Unknown
timestamp: March 27, 2013, 11:56:05 pm
content: For those that want a pretty accurate Amiga workbench experience, seehttp://www.chiptune.com/,this site is amazing and a very accurate clone.

author: AlfBaz
author_rank: Super Contributor
timestamp: March 28, 2013, 06:31:29 am
content: Quote from: gnif on March 27, 2013, 11:56:05 pm

author: sleemanj
author_rank: Super Contributor
timestamp: March 28, 2013, 12:44:28 pm
content: Quote from: gnif on March 27, 2013, 11:56:05 pmBoy that brings back some memories. WB1.3 was amazing back then. I remember the first time I used it, and when I discovered that I was able to multitask! On a system that booted from a single floppy disk. It was, stunning.Funny thing is, using that chiptune demo, the memories are so strong, I swear I can actuallysmellthat first time I setup an Amiga 500 and turned it on (after I had just sold a huge collection of C64 stuff to buy the second hand A500).

author: bitwelder
author_rank: Super Contributor
timestamp: March 29, 2013, 06:37:13 am
content: Quote from: gnif on March 27, 2013, 11:56:05 pmNow I know how my next personal website will look like!

author: Thermal Runaway
author_rank: Contributor
timestamp: April 01, 2013, 11:02:35 pm
content: Quote from: John Larsen on March 24, 2013, 04:25:17 pmHi John - I'm still working on her. I tried to clean up the PLCC socket but the electrolyte has actually damaged the contacts of the pins and my attempts to clean it up with a fibre-tipped pen have failed. No matter how much I rub it down the metal itself seems to have been compromised.I have ordered a replacement PLCC socket, two 74244 logic ICs, a second-hand FAT AGNUS and two diodes. I have removed the damaged components and cleaned the board up with some vinegar (I was going to use isopropyl but apparently you need to use an acidic chemical to neutralise the electrolyte) and my next job is to fit the replacement components.If she's still dead after that I'm out of ideas. Having removed the affected components I can see the full extent of the leakage and it's quite serious - it's got underneath the solder-resist and spread like a cancer across the PCB.Wish me luck!

author: AlfBaz
author_rank: Super Contributor
timestamp: April 01, 2013, 11:10:22 pm
content: Quote from: AlfBaz on March 28, 2013, 06:31:29 amArgh the link was broken because of the comma... and got 404 not found, thought you were trying to be funny with thecurrentamiga WB experience

author: NVX
author_rank: Newbie
timestamp: April 14, 2013, 01:27:03 pm
content: The picture on the "Sam's Workbench Disk!" screen is Asterix and Obelix from the comic Asterix!Someone's definitely had some fun customising that one.