Double your RAM:

[at67]

Nice pics, discreet job like cde's, welcome to the club.

[giobbi]

hi all,

I finally made the 64k upgrade. I decided for a different solution, I put a socket that can be used for both 32k and 64k chips.

Since I hadn't a 32 pin socket (and frankly I'm too lazy to remove a 28 pin socket if I can avoid it ) I decided for a Frankenstein socket: I cut a portion of the socket (pins 1,2,3 and 26,27,28) and I removed it. Then I built the replacement in a MacGyver way:

IMG_20210819_090710.jpg (309.48 KiB) Viewed 3306 times

I lowered the 4 (2+2) extra pins with the Dremel, so they don't touch the board (I checked it out later passing a piece of paper between the pins and the board: the papel have to pass freely behind the pins to be sure they're far enough from the board to prevent any unwanted contact).

IMG_20210819_090700.jpg (99.23 KiB) Viewed 3306 times

The red wire (A15 line) comes from an old, burnt pinball coil; it's very well insulated (it's hard to remove the red coating) and thin enough to pass between two socket pins

IMG_20210827_120524.jpg (384.54 KiB) Viewed 3306 times

And here we have the 64k RAM chip installed:

IMG_20210827_120623.jpg (185.63 KiB) Viewed 3306 times

And of course the Gigatron liked it

IMG_20210827_120739.jpg (708 KiB) Viewed 3306 times

[Sugarplum]

That's a neat way to do that.

[veekoo]

Time to do 64K RAM upgrade mod. I did it from the top of chip.

Now that I have 64K RAM, what are the top applications benefitting from more memory?

btw. I've tested most of the programs marked _64k_

[psergiu]

Upgrade worked fine with a generic 128k x 8 TTL SRAM: MT62C1024P-70L
Could not find a 32-pin socket in parts bin so I soldered AWG30 wires under the RAM chips

[llevet]

You can also replace the HM628128LP-7 (128Kx8) by a TC551001CP-70L or better speed TC551001CP-55L
The advantage for TC551001CP over HM628128LP is it only have half of the power consumption and it exist also in 55ns.

[renzo]

Hello,
to expand the RAM size I installed the Alliance AS6C1008 chip.It is a 128Kx8 as the other one listed in the previous posts.
I connected pin 30 and 32, pin 31 to A15 signal on pcb, and pin 2 to pin 16 (GND).

Since pin2 is fixed to low level state (let's say low half 64k), I expected to see 64KB on the boot screen, insted I get "Gigatron 128K".
Probably I made something wrong even if wiring seems to be correct.

[bmwtcu]

Since pin2 is fixed to low level state (let's say low half 64k), I expected to see 64KB on the boot screen, insted I get "Gigatron 128K".

This is a known issue with ROMv5a. viewtopic.php?p=3182

[renzo]

Hi bmwtcu,

many thanks for the reply. I serched on the forum for a possible bug somewhere, but probably I didn't type the tricky words.