A500 8×44256 (1 RAM=256 KB×4 bit) to 2×514400 (1 RAM = 1 MB×4 bit) possible?

[Blizzard 128 MB]

Hello. A500 8×44256 (1 RAM = 256 KB×4 bit) upgraded to 2×514400 (1 RAM = 1 MB×4 bit) possible? 8×44256 = 1 MB×8 bit, 2×514400 = 1 MB×8 bit. 1 MB chipRAM.
The 44256 and 514400 pin compatible, 20 pins.

[Motormouth]

Hello. A500 8×44256 (1 RAM = 256 KB×4 bit) upgraded to 2×514400 (1 RAM = 1 MB×4 bit) possible? 8×44256 = 1 MB×8 bit, 2×514400 = 1 MB×8 bit. 1 MB chipRAM.
The 44256 and 514400 pin compatible, 20 pins.

Here is what done on an a2000 over on Dave's Amiga Hardware Page
http://members.iinet.net.au/~davem2/overclock/A2000-2MB-chip.html
He used 4 x 44C1000 RAM chips to get 2 megs of Chip ram.

I am guessing you are referring to a 6A motherboard given the ram chips you are suggesting.

What you are suggesting is probably possible but would require at least some minor motherboard hacking.
I would have to look at the motherboard wiring layout.  I am not sure if you could get one one chip to address the full addressing for 0.5 Meg chip or if it would only address 1 Mbit without a minor motherboard modification or which socket to put them in ie 1st and 5th sockets or 1st and 2nd, etc.

Other earlier motherboard versions would need different hacks.

[psxphill]

FWIW I think this hack will prevent you from using a genlock as the original fat agnus in the a500/a2000cr had part of the genlock logic incorporated from the a1000 motherboard, but the 2mb fat agnus in the a500+/a3000 had it split back out again because they needed an extra address input for the cpu access to chip ram (pin 35 changed from xclk to a20). This is what removing the resistors and the connection to gary is for. It's probably possible to reimplement that logic by looking at the differences between the a500 & a500+ schematics, but this hack doesn't appear to do that.

The rest of the hack updates the a2000 motherboard for the 2mb agnus dram changes (pin 56 changed from ras1 to dra9, pin 57 is now the only ras). ras1 goes to ras on the 2nd (now unused) bank of ram, so the hack routes that to pin 5 of the 1st bank. Pin 5 on the old ram chips is a "No Connect" but is now a9. I'm guessing the connection from a9 to +5 through a resistor is because the address pins need external pull ups but the ras doesn't, but I haven't bothered investigating further.

I'm surprised this hack wasn't documented earlier, but the lack of genlock (which IIRC the megachip upgrades do handle properly) might have been a reason. Plus the megachip upgrades were an easier sell, popping a couple of chips and one wire is much easier than removing all the ram and doing all that rework to the board.

[Blizzard 128 MB]

I do not want to expand the memory. A500 rev. 6A, 8372A = max. 1 MB chipRAM.
2 MB chipRAM not possible, 2 MB Agnus not possible.
I want to use 2 piece 441000 chips instead of 8×44256 chips.
This possible with A500?
C64 8×4164 = 2×4464 work.

[psxphill]

I do not want to expand the memory. A500 rev. 6A, 8372A = max. 1 MB chipRAM.
2 MB chipRAM not possible, 2 MB Agnus not possible.
I want to use 2 piece 441000 chips instead of 8×44256 chips.
This possible with A500?
C64 8×4164 = 2×4464 work.

2mb chip ram appears to be possible if you hack the board and use the right 2mb agnus (there are two 2mb agnus variations, one is compatible but the other has a much different pin out that definitely won't work). But if you don't want to replace agnus then your maximum is 1mb.

Using 441000 without a 2mb agnus is going to be hard, but it might be possible. Google doesn't throw up anything, so you're on your own figuring out the logic to calculate the extra address lines from the chip selects. If you are keeping the old agnus then you probably ought to have one chip in each of the banks (the 2mb agnus hack has the second bank completely empty).

I couldn't find a c64 hack for 2x4464, the only result I found was someone saying they killed their c64 trying.

[Blizzard 128 MB]

C64 wide, or Plus4 8×4164 motherboard to 2×4464 possible.
4×4164 = 1×4464, look: http://postimg.org/image/rqwr8xazd/
https://upload.wikimedia.org/wikipedia/commons/2/28/Plus4_main_board.jpg
C128 or plastic C128D 16×4164 = 4×4464 work.
http://3.bp.blogspot.com/-tcXwDf0AWk8/VEymT3rS82I/AAAAAAAADSE/s3_yXl7QWak/s1600/128K%2BDRAM.jpg
C128DCR originally 4×4464.

8×44256 to 2×441000 too complicated.

If A2000 1 to 2 MB chipRAM possible, then A500 6A motherboard 1 to 2 MB chipRAM possible.
http://members.iinet.net.au/~davem2/overclock/A2000-2MB-chip.html
Continue here:
http://www.amiga.org/forums/showthread.php?t=70075

[Blizz1220]

Not so sure but even if you managed to put bigger memory chips in
there I think they would be be used up to 50 % capacity and that is in
case in works.They tend to get hot too.

Good source of Amiga compatible memory for extra chips are old S3 ISA
Virge cards , just google which ones are compatible.