EEVBlog #438 - Amiga 500 Retro Computer Teardown

[EEVblog]

Vintage Teardown Tuesday.
What's inside the 1987 Commodore Amiga 500 computer.



Dave.

[JoannaK]

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_Miner

There are so much memories, so much info .. A lot most likely forgotten by now.

[justanothercanuck]

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. 

[moemoe]

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 @7m25

And your Amiga is lucky, many of them have lost their knobs to eject the floppy.

Btw, schematics are available at http://project64.c64.org/hw/amiga.htm

[JoannaK]

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. 

I 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).

[Nack486]

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.

[sleemanj]

*sniff* /me wipes away tear

Owned, 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.

[dgarlans]

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

[nharrer]

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... 

[Skimask]

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.

[justanothercanuck]

I intend to transplant modern hardware into the cases.

Can't say I'm happy about hearing that, but to each their own... 

[baoshi]

The solder mask looks like printed using silkscreen process hence the bumpy grids.

[Winston]

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_Miner

Jay 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.

[obsoletemac]

For a good read about commodore, check out "On the edge" (http://www.amazon.co.uk/The-Story-Commodore-Company-Edge/dp/0973864907)


//c

[andersm]

For a good read about commodore, check out "On the edge" (http://www.amazon.co.uk/The-Story-Commodore-Company-Edge/dp/0973864907)

Be sure to get the second edition though, it contains some extra material. The sequel, which deals specifically with the Amiga era, is due out later this year.

[Kaluriel]

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

[John Larsen]

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 

[Ferroto]

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.

[jaycee]

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.

[Plecharts]

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: [Select]

https://www.youtube.com/watch?v=HKNVIgsbYrA&t=24m50sEDIT: The forum doesn't like linking in the exact time in the YT URL...

[jaycee]

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.

[Plecharts]

Technically thats not a bodge wire - just ensuring that the case of the oscillator is connected to shield ground.

Please explain why it would need to be connected to ground, I don't see any reason why the crystal wouldn't work without it.

[jaycee]

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.

[Big_Al]

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. 

[MartinX]

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.