Amiga 500 r5 1MB Chip ram - Agnus mod how to

E406 - Mr T Sends his Amiga 500 in for a 1MB agnus mod he purchased way back in Jan 1993. original reciept and all. But the belly ram board has a VARTA! however its a sealed square job that needs to be removed. I show how to mod the motherboard X-Ram signal to use the Belly 512k to go to 1mb chipram.
Tools used in this video:
Tonya - a hammer
Jonard IC extractor
www.amazon.com/Jonard-EX-2-Ex...
"DIP Pin Straightener"
retrorewind.ca/dip-chip-strai...
"Helmet of Goober!"
www.amazon.com/Headband-Magni...
"Chinesium" solder rework station “853D”
www.ebay.com/itm/313701800310
Siglent SDS1052DL digital oscilloscope
www.amazon.com/Siglent-Techno...
Kotto silicon solder sucker aka "Moana3 with the DSL"
www.ebay.com/itm/203339405333
TV pixel display and wall pixel display
www.divoom.com
like the wall neon? get it here
www.retroledsigns.com
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[@RavenWolfRetroTech]

Nice blast from the past Chris! I did this upgrade for all my friends and a few club members back in the day.

[@thomasdaniels4576]

Thanks again Chris for the work you did on my A500 motherboard. As always, wonderful and informative videos. It has been so long since I used my Amiga 500 that I did not even remember there being a battery on the memory expansion board. Thanks for removing the battery.

[@CoyoteSeven]

Reminds me what I had to do to install my Megachip onto my A-2000. It was a rev 4 mobo, your favorite.

[@pkf4124]

Remember seeing those Varta batteries on Pc cards back in the late 90’s early 2k’s. They were often leaky then. The Varta logo just fills me with dread every time I see it.

[@ralfr.5974]

I hate the old Batteries 🤮 on All PCB`s Great Video Again 👍🏻🍻🤩

[@daishi5571]

Laughed so hard at the floppy sniff.

[@jjdigitalvideosolutionsllc5343]

Wow, the prices! If I could turn back time...

[@memadmax69]

$469.95 was alot of money back then... That was a month of rent plus a car payment lol

[@daishi5571]

Was it? 1990 Mac Classic $999 - 68000 CPU, 1MB RAM, no HDD, only capable of B&W graphics on it's non upgradeable 9" screen, single tasking memory chomping OS. The much more capable A2000 wasn't just a bargain, it was a gift. Rent and car payments pah.... 😀

[@i0Retro]

If your ram expansion has a enable/disable jumper, you can use that and don’t need to cut the xram trace. I have a rev5 with three state switch that allows to select between chip/slow/none

[@ChrisEdwardsRestoration]

Never downgraded

[@gertsy2000]

The clandestine varta!

[@mikegravgaard340]

That Varta is either a tombstone or the 2001 obelisk.

[@keyboard_g]

I hate the idea of scratching out traces. Would be great if it was just a jumper across those pads and address lines.

[@boydpukalo8980]

Nice clean board - how it’s spoda be.

[@James_T_Quirk]

Great Work, Again Chris, But as somebody who has had a Bowel Reconstruction, due to Meat Pies, Coke & Computers, the Rubber gloves are unnerving .. & A500 FDD Cables are always that Tight ..

[@anakondase]

I did this conversion on my Rev 5 in the early 90s. I don't remember why but I have a little plastic slip on one of the pins in the upper row on the 8372A. I suppose that wasn't needed then?

[@ChrisEdwardsRestoration]

Nope

[@anakondase]

@@ChrisEdwardsRestoration Great, I wonder why it was suggestet then. Can't really find any info about that now.

[@josephphillips9243]

For a newbie like me does that mean all Rev 5, will need to be circumcised even with the most recent upgrades on sale?

[@ChrisEdwardsRestoration]

No but if you want to run a newer rom and have 1mb chip then yup

[@josephphillips9243]

@@ChrisEdwardsRestoration Thanks Chris

[@RetroJay1974]

Would you be able to scan those documents and upload/archive them somewhere please? I have 3 x A500 Rev5's in need of agnus and fam upgrades.

[@ChrisEdwardsRestoration]

Its as simple as i showed. The documents are back with its original owner. This was april

[@thomasdaniels4576]

I am the owner of the A500 motherboard. If you are interested in the documents I can pass them along to you.

[@wimwiddershins]

Er, could I please see the small asian lady doctor? (The one with tiny hands)

[@DonSolaris]

What is the benefit of 1MB Chip RAM? Does A500 with 1MB chip RAM becomes faster vs A500 with 512k + 512k expansion?

[@ChrisEdwardsRestoration]

chip ram is faster than the slowram of the belly slot. by remapping the A20 xram signal to Agnus you can run programs designed for the later 1mb chipram boards. you can still have up to 8MB fastram on the zorro expansion slot. and removing the belly 512k makes the machine a 512k chipram machine again. no harm done only benefits.

[@DonSolaris]

@@ChrisEdwardsRestoration Thank you! I'm curious why does SysInfo show no difference in speed between the two setups? I have one Amiga with 1MB chip, one with 512+512. Yet get exact same results.

[@ChrisEdwardsRestoration]

"magic and science" @@DonSolaris some programs require the addressing of 1mb chip how they are coded. on a old 500 i dont think is really faster at all. its just how the ram is addressed to agnus to handle more screenmodes and the magic that it does itself as a custom chip. you wont see any speeds at all worth a crap on a old Amiga 500 at 7mhz..

[@DonSolaris]

@@ChrisEdwardsRestoration Thanks!!

[@tokul76]

not possible to install actual jumpers in JP2 place?

[@ChrisEdwardsRestoration]

Yes but you usually never downgrade

[@mihajlo20m]

I remember installing a switch on a500 that worked as a jumper, because there were some games that didnt work with 1MB chip ram

[@jondoough]

Any USA sellers of the Amiga 8372a 318069-02 ?

[@ChrisEdwardsRestoration]

Not that i know of besides ebay usa sellers. Anal logic still sells them at exorbitant prices