ECS Upgade for A500

[weirdami]

I finally was able to plug this thing in and I discovered that the switch controls making it boot to an "insert workbench v1.3" hand screen and a "2.8 Roms (37.175)" disk inserting itself animation screen. That's probably 2.0, not 2.8, but I'm running it with the black and white out to a television through a vcr and it looks like an 8. :-/ Anyhoo, I guess "ECS Upgrade" means you get ECS chip set. And the switch is for toggling between OCS and ECS. Neat.

Now, someone can tell me what company made this gizmo, or if some A500's came like this from Commodore. Maybe I'll try putting in some disks and trying that showconfig idea.


edit: Yup, showconfig shows "ECS NTSC Agnus" and "Normal Denise".

[Zac67]

Switching ECS/OCS would only be possible with severe modifications and overlay boards. I guess this switch just relocates Ranger Mem $C00000 to $080000 for 1 MB Agnus which makes an ECS Agnus near 100% compatible.

[Ideal]

weirdami wrote:
I discovered that the switch controls making it boot to an "insert workbench v1.3" hand screen and a "2.8 Roms (37.175)" disk inserting itself animation screen.

Yes, this is what is called a ROM SWITCH.
This would allow you to mount a 1.3 rom in one socket, and a 2.04 rom in the other, and then you could select from a switch, so as to get maximum compatibility as some games would only run under 1.3.

weirdami wrote:
I guess "ECS Upgrade" means you get ECS chip set. And the switch is for toggling between OCS and ECS. Neat.

No. The switch does no such thing. As I said the switch merely selects which rom to boot.

weirdami wrote:
edit: Yup, showconfig shows "ECS NTSC Agnus" and "Normal Denise".

Your conclusion is all wrong.

What this means is as follows. On older Amiga 500 boards you could not get 1mb chip ram. You had 512k on the motherboard, and then when you put in another 512k this will make you have 512k chip and 512k other mem.

This is because the earlier amiga 500 came with 8371 agnus chips, which only support 512k.

So now we come to the part with the ECS NTSC Agnus.

To be able to get 1 meg chip ram, you would then replace the 8371 agnus with the 8372A agnus, and then cut one line on the motherboard near the ram expansion, and cut a connection on JP2 near the ROM, and then you'd be able to have 1 meg chip ram.

And now for the rest of your theory.
You say you have an NTSC Agnus. Why does it say NTSC Agnus? Well let me tell you.

When you mount a 8372A Agnus in a Rev 5 or earlier motherboard, this Agnus will automatically be detected as NTSC. Pin 41 on the agnus will decide if it is NTSC or PAL, and on Rev 5 and earlier pin 41 is grounded.

(I actually worked with this just a few hours ago, and disconnected pin 41 on a 8372A to get PAL mode on one of my A500's, so I know.)

The fact that they have written ECS agnus on there is of little consequence.

So, in short:
The switch only selects the rom to boot, and the reason it says ECS in showconfig is because they've replaced the Agnus with 8372A.

Edit:
There is a description of this mod on aminet, with "drawings":
http://aminet.net/package/hard/hack/1MBChip

[Tenacious]

How much chip ram is reported in the title bar?  In ShowConFig?  I'm betting the previous owner completed the 1 Meg Chip modification.

Out of curiousity, I've seem you around for a long time, how have you been getting your Amiga 'fix' before acquiring this machine?

[weirdami]

@Tenacious

When I booted it with ECS on, I remember seeing 800 something KB chip RAM and zero "other". So, I figured it was 1MEG.

[Tenacious]

@ weirdami

Sounds right to me.

[melange]

The 8371 Agnus could handle 512k or 1MB chip, but was not and ECS agnus!  You needed to get at least an 8372A to go ECS.  I upgraded a number of peoples A500's that contained 8371 Agnus from (512k Chip / 512K Slow mem) to 1meg chip, many years ago, simply by cutting and joining jumper pads.  Was very easy.