List of A500 mobo revisions and appropriate chips?

[Photon]

Just gave a rev 6A A500 a new PicoPSU. <3

All my A500s were bought from others except two that I've kept since back in the day, and this is not one of those two. One is in the infirmary awaiting diagnosis.

Therefore, is there a handy list where everyone can check which chips (including Kickstart) "belong" on which revision motherboard?

Some A500 models had A500+ chips, I know. Still, if there's some official list (assuming previous owner, or C-Amiga didn't pull some tricks when it was at its peak)?

Just so that everything is proper and good.

[Jope]

I don't think there is a general list.

Here's a rough guide:
Rev 3: OCS Denise, OCS Agnus, often Toshiba Gary but the last ones might have a CSG Gary, Kick 1.2, power LED goes off
Rev 5: OCS Denise, OCS Agnus, CSG Gary, Kick 1.2 and 1.3, power LED goes off
Rev 6: OCS Denise, 1MB Agnus, CSG Gary, Kick 1.3, power LED goes dim
Rev 8: ECS Denise, 2MB Agnus, CSG Gary, Kick 1.3 or 2.04, power LED goes dim

[rjd324]

The Rev 5 will work okay if you give it a 1MB Agnus?

[Jope]

Originally Posted by rjd324

The Rev 5 will work okay if you give it a 1MB Agnus?

It is possible to use one, yes. The Rev 5 always grounds the PAL/NTSC pin of a 1MB Agnus, but a sliver of kapton tape over it should isolate it from the socket if you have a PAL machine.

[Photon]

Yes.

Originally Posted by Jope

I don't think there is a general list.

Here's a rough guide:
Rev 3: OCS Denise, OCS Agnus, often Toshiba Gary but the last ones might have a CSG Gary, Kick 1.2, power LED goes off
Rev 5: OCS Denise, OCS Agnus, CSG Gary, Kick 1.2 and 1.3, power LED goes off
Rev 6: OCS Denise, 1MB Agnus, CSG Gary, Kick 1.3, power LED goes dim
Rev 8: ECS Denise, 2MB Agnus, CSG Gary, Kick 1.3 or 2.04, power LED goes dim

<3 but isn't Rev. 8 always A500+? I ask only about A500.

Hey BTW o/

Maybe formalize. (Below is not about the Rev 6 mobo in title, but it would be neat with a list.)

1. PAL=8371, all A500 until rev 6. Right?
2. Zero chances of haxing 1MB chip with 8371. Right? (Side project)
3. Kick 2.0 was only installed in A500+, no A500 ever. Right?

I'm asking provokingly to get answers, I know. And still only official products from factory.

[zipper]

They did castrated rev 8 boards as A500 - demand was there but no A500 boards anymore.

[Photon]

Originally Posted by zipper

They did castrated rev 8 boards as A500 - demand was there but no A500 boards anymore.

Interesting. So can we confirm someone bought a new A500 (around 1991 I guess) that came with a Kick 2.0 factory installed? Any country. (USA, UK, Germany likely first on the list)

Actually Kick 2.0 is less of a point than the handling of slowmem. Let's make it both then. A500s with Kick 2.0 and slowmem gets mounted as chipmem in hardware. Else we need castration details

[4pLaY]

Originally Posted by Jope

I don't think there is a general list.

Here's a rough guide:
Rev 3: OCS Denise, OCS Agnus, often Toshiba Gary but the last ones might have a CSG Gary, Kick 1.2, power LED goes off
Rev 5: OCS Denise, OCS Agnus, CSG Gary, Kick 1.2 and 1.3, power LED goes off
Rev 6: OCS Denise, 1MB Agnus, CSG Gary, Kick 1.3, power LED goes dim
Rev 8: ECS Denise, 2MB Agnus, CSG Gary, Kick 1.3 or 2.04, power LED goes dim

There is also a Rev7 (I have one of them) but I am not sure what the differences are and they are quite rare. I got this one from the UK though, so it was sold there at least.

[Photon]

Originally Posted by 4pLaY

There is also a Rev7 (I have one of them) but I am not sure what the differences are and they are quite rare. I got this one from the UK though, so it was sold there at least.

Yeah, sorry for mentioning rare boards that are hard to find. Rev7 may have been a transition A500+ motherboard also, depending on components. What does yours have on it?

[hooverphonique]

Originally Posted by Photon

Interesting. So can we confirm someone bought a new A500 (around 1991 I guess) that came with a Kick 2.0 factory installed? Any country. (USA, UK, Germany likely first on the list)

Actually Kick 2.0 is less of a point than the handling of slowmem. Let's make it both then. A500s with Kick 2.0 and slowmem gets mounted as chipmem in hardware. Else we need castration details

As far as I know, The A500's with rev 8 boards were configured just like an A500 - 512KB chip, 512KB slowfast if you add a trapdoor expansion, no clock/battery, Kick 1.3.
I'm not sure which Agnus got fitted though, but probably a 2MB capable one (8375?).

[ajk]

I've got two A500 systems with a rev8 board, and I would agree with the above. They match the specs of a regular A500, not A500+. I'm guessing Commodore had spent up all the earlier motherboards, but there was still commercial demand for the plain A500.

However, I haven't had these from new at all, they are later purchases. I could check exact chip revisions if it is of interest, but it won't be 100% reliable.

[Jope]

The rev8 is only compatible with the 2MB Agnus, so that's what the rev8 A500s (non plus) got. :-) Mine came with a super denise (the seals were intact when I got it). The board is configured for 512k chip on the motherboard and 512k slow in the trapdoor and kickstart 1.3. RTC unpopulated on the motherboard. The badge on the case is like the wide A500 plus badge, but only says A500 on it. Green power LED.

[4pLaY]

Originally Posted by Photon

Yeah, sorry for mentioning rare boards that are hard to find. Rev7 may have been a transition A500+ motherboard also, depending on components. What does yours have on it?

I guess it was a short lived rev, from 6A to 8. It is not a machine I have in use, so I will need to digg it out of my storage area to check.

[Jope]

Here's pictures I was sent by someone. Perhaps 4play? http://jope.fi/amiga/a500rev7/

Looks like a 512k Agnus was fitted, and there is no RTC, so this implies that it is closer to a rev 6 than rev 8.

[Photon]

Originally Posted by Jope

Here's pictures I was sent by someone. Perhaps 4play? http://jope.fi/amiga/a500rev7/

Looks like a 512k Agnus was fitted, and there is no RTC, so this implies that it is closer to a rev 6 than rev 8.

Informative, thanks!

My Rev 6A's has 512K chip + slowmem, 8372 Agnus, and white 1MB chip RAM mask symbols on the motherboard, like in the pictures.

I'm filled with questions now I've also been away from Amiga for a spell, so sorry if they're newb questions.

- Wasn't there a kick 2.0 A500 then? Rev7 pictures seem to show a kick 1.3. (Wikipedia says no. I guess we must have bought them as an upgrade and swapped them.)

- Can you have 1MB chip + trapdoor RAM on any A500? (I guess not, since it requires 8372 and this will always map extra RAM as chipmem?)

- ... But the "always" is just not true, since my Rev 6A's have 8372 and keeps slowmem as slowmem.

- Can an 8371 Agnus be retrofitted to an unmodded Rev 6A board without conflict with the other chips or incompatible with some software? (The Rev7 seems to have done so?)

- Did Rev8 have RTC then, and was it the only A500 revision to have it?

[ajk]

The rev 8 boards in A500 systems don't have the RTC components (and therefore fortunately also no battery) installed. These are of course easily added to the board if needed.

I've got some photos in an old thread of mine where you can see all the RTC related stuff completely untouched.

[Jope]

Originally Posted by Photon

- Wasn't there a kick 2.0 A500 then? Rev7 pictures seem to show a kick 1.3. (Wikipedia says no. I guess we must have bought them as an upgrade and swapped them.)

True, none from the factory. Us "power users" swapped them in ourselves.

- Can you have 1MB chip + trapdoor RAM on any A500? (I guess not, since it requires 8372 and this will always map extra RAM as chipmem?)

You need to build an additional circuit to enable this. Many oversized trapdoor expansions had a Gary board that handled that stuff.

- ... But the "always" is just not true, since my Rev 6A's have 8372 and keeps slowmem as slowmem.

The easy choices there are 1MB chip or 512/512. They didn't configure them for 1MB chip from the factory, probably due to compatibility reasons.

- Can an 8371 Agnus be retrofitted to an unmodded Rev 6A board without conflict with the other chips or incompatible with some software? (The Rev7 seems to have done so?)

It is fully compatible. You will be limited to 512k of chip after that.

- Did Rev8 have RTC then, and was it the only A500 revision to have it?

As ajk said, if the rev8 board was in a computer with an A-500 badge, no RTC was populated and there is only 512k of RAM. If the board was on an A-500 plus case, the RTC + battery were installed and a full 1MB is on the board.

For the downgraded rev8 A-500, one TTL chip is also missing and some jumpers are in a different order for it to be a 512 mobo/512 trapdoor setup. The jumpers can be adjusted, the missing RAM chips and the TTL chip added for it to become an A500+ with 1MB on the mobo and 1MB possible in the trapdoor. Instructions are pretty easy to find here on support.hardware.

[hooverphonique]

Originally Posted by Photon

Informative, thanks!
- ... But the "always" is just not true, since my Rev 6A's have 8372 and keeps slowmem as slowmem.

Where in the memory space the trapdoor expansion ends up is configured by motherboard jumpers - it isn't affected by agnus revision (but you still need a 8372a for 1MB chip, of course).

[Photon]

Originally Posted by ajk

I've got some photos in an old thread of mine where you can see all the RTC related stuff completely untouched.

Very tidy.

I have an A500 with accelerator and two stock(?) ones. The warranty seal having been broken on both is the whole background for my questions. I just want a good grip again on exactly what was manufactured and sold.

That way, I can first make sure it's stock and then figure out what I can change.

(re: 8372)

Originally Posted by Jope

The easy choices there are 1MB chip or 512/512. They didn't configure them for 1MB chip from the factory, probably due to compatibility reasons.

It feels like the size of each type of RAM shouldn't cause a hardware incompatibility. Strange. Maybe slowmem was hacked in to allow it at all, and now a different solution is required to do it properly. It shouldn't require more ICs, since it handles both types. Either way it was good to support internal fastmem even in the form of slowmem, it enables quite a few things OS-wise.

(re: 8371)

Originally Posted by Jope

It is fully compatible. You will be limited to 512k of chip after that.

ACA500Plus requires 8372 to get 1MB chip, and I want this for my almost-stock work machine. But I might set up an A500 for circa 1988 demos maybe even with kick 1.2, and then use 8371 to run demos with "incorrect" Copper lists and Blitter inits.

Originally Posted by Jope

As ajk said, if the rev8 board was in a computer with an A-500 badge, no RTC was populated and there is only 512k of RAM. If the board was on an A-500 plus case, the RTC + battery were installed and a full 1MB is on the board.

Yup, so all Rev 8 are A500 not A500+, and no A500 came with RTC. Very interesting with the A500+ legend on the pure-A500 mobo

Originally Posted by Jope

For the downgraded rev8 A-500, one TTL chip is also missing and some jumpers are in a different order for it to be a 512 mobo/512 trapdoor setup. The jumpers can be adjusted, the missing RAM chips and the TTL chip added for it to become an A500+ with 1MB on the mobo and 1MB possible in the trapdoor. Instructions are pretty easy to find here on support.hardware.

So again, Rev8 mobos even though they say A500+ are still pure A500 boards and you have to mod it to get A500+ behavior.

Hmm, one more curious question

Originally Posted by Jope

Rev 6: OCS Denise, 1MB Agnus, CSG Gary, Kick 1.3, power LED goes dim

Since I have this and get 1MB Chip, how is ECS Denise not required? It already can read from addresses in the 512k-1MB chip range, or all addressing is done by Agnus so that no other ECS chips are required (e.g. Paula)?

[Jope]

Originally Posted by Photon

It feels like the size of each type of RAM shouldn't cause a hardware incompatibility. Strange. Maybe slowmem was hacked in to allow it at all, and now a different solution is required to do it properly. It shouldn't require more ICs, since it handles both types. Either way it was good to support internal fastmem even in the form of slowmem, it enables quite a few things OS-wise.

Lots of cracks and some original SW expect 512k of RAM at c00000 and just won't accept 1MB chip to be 1MB of RAM total, instead thinking that the machine has no RAM expansion.

So not HW, but SW compatibility reasons.

Since I have this and get 1MB Chip, how is ECS Denise not required? It already can read from addresses in the 512k-1MB chip range, or all addressing is done by Agnus so that no other ECS chips are required (e.g. Paula)?

Agnus is the chip that feeds the other chips using DMA, Paula and Denise don't touch the RAM themselves.

Super Denise's reason to exist is that it supports higher horizontal frequencies than 15kHz. So if you're happy with PAL/NTSC (everyone running ECS should accept this fate), a regular Denise can be used even with a 2MB Agnus just fine.