SOLVED: How to Increase SRAM on an SA1 Board?

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X2Whiskey
Posts: 5
Joined: Wed Aug 14, 2019 4:04 pm

SOLVED: How to Increase SRAM on an SA1 Board?

Post by X2Whiskey »

Hello,

I'm looking to convert the 256 kbit SRAM on a SHVC-1L5B-20 PCB to 1 Mbit SRAM and am looking for some direction. When comparing chip pinouts, I see the 256Kb is 28 pins while the 1Mb is 32 pins. I also see that pin 28 of the 256 (VCC) conflicts with pin 30 of the 1Mb (CE2). Does that mean I should isolate pin 30 (CE2) of the 1Mb? And where should I route that pin connection to?

Since seeing Voultar's Video https://www.youtube.com/watch?v=ImH8B1cG3p0 on YT, I have on a personal quest to make my own Gradius III reproduction incorporated with Vitor Vilela's SA1 enhancement hack https://github.com/VitorVilela7/SA1-Root. Unfortunately, I think think that video has a lot of misleading information which I think is odd considering the author's reputation and experience.

So, I've identified a suitable donor PCB from the Japanese Super Famicom game Mini Yonku Shining Scorpion https://www.pricecharting.com/game/supe ... g-scorpion. It comes with the SHVC-1L5B-20 revision PCB that has a SOP-28 256 kbit SRAM, and solder mask-covered pads allowing for the mounting of a larger SOP-32 SRAM. Oh, and this cart can be had for under $10 shipped from Japan through EBay.
Last edited by X2Whiskey on Fri Aug 16, 2019 4:31 am, edited 1 time in total.
Ice Man
Posts: 547
Joined: Fri Jul 04, 2014 2:34 pm

Re: How to Increase SRAM on an SA1 Board?

Post by Ice Man »

I just build a Gradius III on SA-1 but using a SHVC-1L3B-10 PCB instead.

For SHVC-1L5B-XX PCB just solder it in as is since CE2 is tied VCC afaik.
Attachments
sram-gradius.png
X2Whiskey
Posts: 5
Joined: Wed Aug 14, 2019 4:04 pm

Re: How to Increase SRAM on an SA1 Board?

Post by X2Whiskey »

Thank you for the input.

I just spent some time looking up and comparing SRAM datasheets as well as doing some pinout tracing on the SHVC-1L5B-20. The notes I've taken so far are in the attached image. Everything seems to correlate to what you've said, but I see one inconsistency. The 1Mb SRAM datasheet denotes pin 1 as NC (Not Connected), but the SHVC-1L5B-20 has that pin pad hardwired to the SA1's pin 104.

Should the 1Mb SRAM pin 1 be left floating?
Attachments
SA1 SRAM Upgrade Notes.jpg
Ice Man
Posts: 547
Joined: Fri Jul 04, 2014 2:34 pm

Re: How to Increase SRAM on an SA1 Board?

Post by Ice Man »

NC means internally not connected. It does not matter where you connect that pin or leave it floating. It won't do anything at all.
X2Whiskey
Posts: 5
Joined: Wed Aug 14, 2019 4:04 pm

Re: How to Increase SRAM on an SA1 Board?

Post by X2Whiskey »

So to wrap things up: I cleaned the solder mask from the PCB's extra traces and soldered in the 1Mb SRAM with no special trace cutting or rewiring and all is working fine. Hopefully this proves useful for others having the same questions.
pausuri
Posts: 9
Joined: Wed Oct 02, 2019 2:24 pm

Re: SOLVED: How to Increase SRAM on an SA1 Board?

Post by pausuri »

X2Whiskey wrote:So to wrap things up: I cleaned the solder mask from the PCB's extra traces and soldered in the 1Mb SRAM with no special trace cutting or rewiring and all is working fine. Hopefully this proves useful for others having the same questions.
That's really good that you managed to sort it out.
I want to do the same, can I have a link to buy the 1 Mbit SRAM spare part??

If is it not much trouble, could you upload a picture of the pcb with the fitted new ram??

I really appreciate it!!

Thanks
hidden0
Posts: 17
Joined: Wed Dec 29, 2021 1:28 am

Re: How to Increase SRAM on an SA1 Board?

Post by hidden0 »

X2Whiskey wrote: Thu Aug 15, 2019 6:28 am Thank you for the input.

I just spent some time looking up and comparing SRAM datasheets as well as doing some pinout tracing on the SHVC-1L5B-20. The notes I've taken so far are in the attached image. Everything seems to correlate to what you've said, but I see one inconsistency. The 1Mb SRAM datasheet denotes pin 1 as NC (Not Connected), but the SHVC-1L5B-20 has that pin pad hardwired to the SA1's pin 104.

Should the 1Mb SRAM pin 1 be left floating?
but if you are coming from 1L3B

Since couldn't find accurate info around for 1L3B-xx boards
Would like to Add in case of 1L3B-xx boards ,

I used IS62C1024AL , You can also use Other 1mb variants.

Pins on the chip are quite wide but it can be Squished and chip can be installed on the original sram pads.

Install the Sram with Pins 1/2/3/28/31/32 Lifted with the Pins 1/2/31/32 Hanging out.


Pin 1 of IS62C1024AL NC will go to SA-104 (Via available)
Pin 2 of IS62C1024AL A16 Will go to SA-86 Directly to the chip
Pin 3 of IS62C1024AL A14 Will go to SA-87 Directly to the chip
Pin 28 of IS62C1024AL A13 Will go to SA-103 (via available)
Pin 31 of IS62C1024AL A15 Will go to SA-105 Directly to the Pin
Pin 32 of IS62C1024AL VCC Will go to Any VCC used C5 smd cap to get the Vcc

Image
Last edited by hidden0 on Fri Jan 20, 2023 4:10 pm, edited 1 time in total.
X2Whiskey
Posts: 5
Joined: Wed Aug 14, 2019 4:04 pm

Re: SOLVED: How to Increase SRAM on an SA1 Board?

Post by X2Whiskey »

@pausuri, My apologies for not responding sooner. I think I rotated on to another one of my hobbies shortly after completing this and completely forgot about this post. I just received a notification about it in my email.
pausuri wrote: Mon Oct 07, 2019 2:40 pm I want to do the same, can I have a link to buy the 1 Mbit SRAM spare part??
Surprisingly, I was able to find my receipt. I got it from Mouser, here's the page: https://www.mouser.com/ProductDetail/IS ... cycode=USD.
pausuri wrote: Mon Oct 07, 2019 2:40 pm If is it not much trouble, could you upload a picture of the pcb with the fitted new ram??
No cut traces and no jumper wires needed.
No cut traces and no jumper wires needed.
The battery is not used in this game so I removed it to clean things up.
The battery is not used in this game so I removed it to clean things up.
Funny thing, I was just playing this cart a few days ago. The game runs so good in this configuration!
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