Author Topic: Question regarding the 512kb sram chips  (Read 14843 times)

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Offline infidelity

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Question regarding the 512kb sram chips
« on: July 15, 2017, 06:56 PM »
I've asked krikzz a few years ago, if he would consider a revision of his n8 everdrive , to include 2 1024kb sram chips for the prg & chr roms. He told me it's more than that, but wouldn't specify more.

My idea was to see if those 512kb chips could be removed, and replaced with 1024kb chips, so my games that I created on the MMC5  (Zelda - The Legend of Link & Super Mario All-Stars NES) will work on the N8. Is there anybody here that is skilled enough, that would attempt to see if installing the 2 1024kb chips would work to support 2mb roms?

If this is impossible, meaning there's more to it than just replacing the smaller chips with larger ones, than could someone please elaborate what else is required. Because the 1mb limit is the only reason stopping me from purchasing this device.

Here is the product I'm looking at.

http://www.mouser.com/Search/m_ProductDetail.aspx?qs=HMZ41YbsgBrybmnvsRdcdQ%3d%3d
« Last Edit: July 15, 2017, 07:33 PM by infidelity »

Offline KRIKzz

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Re: Question regarding the 512kb sram chips
« Reply #1 on: July 17, 2017, 02:05 PM »
Chip replacement will not work, because upper bit of address bus will not be controlled by cartridge. You still will have only 512K, even with 1MB chips

Offline infidelity

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Re: Question regarding the 512kb sram chips
« Reply #2 on: July 17, 2017, 02:24 PM »
Is it possible to make the cartridge control the upper bit of the address bus, to allow useage for larger chip support?

Is this a firmware thing, or is there additional hardware needed on the N8 board? And thank you for replying and being specific.

Offline KRIKzz

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Re: Question regarding the 512kb sram chips
« Reply #3 on: July 17, 2017, 02:46 PM »
It require firmware and hardware update. At the hardware side required one extra address wire connected to FPGA

Offline infidelity

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Re: Question regarding the 512kb sram chips
« Reply #4 on: July 17, 2017, 03:46 PM »
Ok, the hardware aspect sounds like I could do on my end to modify the cartridge.

On the firmware end, would this be a difficult code to implement on your end? If it's not, would you be willing to make the nessecary additional code, so I could flash that to the N8 cartridge, and a schematic from where the additional wire needs to be soldered to, from the FPGA chip?
« Last Edit: July 17, 2017, 03:49 PM by infidelity »

Offline Lord-Raziel

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Re: Question regarding the 512kb sram chips
« Reply #5 on: July 20, 2017, 09:58 PM »
I'm still waiting for that Everdrive N8 v2 too, I have been wanting buy another flashcart (I have Everdrive 64 v2 and SD2Snes and I'm very satisfied with Krizz's support) and N8 has been considered, but since I have many nes/famicom cartridges in my collection basically I want the Everdrive N8 for playing rom hacks, most interesting ones exceed the supported capacity of the PGR and CHR of current N8 flashcart :(

Offline infidelity

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Re: Question regarding the 512kb sram chips
« Reply #6 on: July 22, 2017, 02:20 PM »
Well I hope krikzz responds to my last post in this thread. Cause from the explanation he gave, the concept sounds possible. I own his latest products for my N64, Genesis, and the sd2snes cart. I really want the N8, but the size needs to be expanded for me to purchase this.

Offline relic

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Re: Question regarding the 512kb sram chips
« Reply #7 on: July 28, 2017, 06:13 AM »
A 2MB / 16Mbit version of the Everdrive N8 would rule. Always seemed strange to me that was never the default configuration.

Offline infidelity

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Re: Question regarding the 512kb sram chips
« Reply #8 on: July 29, 2017, 02:17 AM »
It would be great indeed. I know it's mostly geared toward commercial games, but my knowledge and useage of the mmc5 mapper, would really benefit from the N8 having 1024kb chips, making it so you don't have to destroy authentic mmc5 cartridges. I just wish krikzz got back to me, we had a good exchange going on here, but idk where he went, I also waited a few days to send him a pm about my last question here, but haven't heard back. :-/

Offline relic

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Re: Question regarding the 512kb sram chips
« Reply #9 on: July 29, 2017, 04:02 AM »
It would be curious to see if the IRQ problem in Super Mario Bros. 3 in Super Mario All-Stars MMC5 is present when run on an Everdrive (or PowerPak, but we're not on NintendoAge). The latest version has the IRQ pretty bad on an MMC5 cartridge and white/red Famicom system. We need Krikzz back in here.

Oh and thanks for your work on Legend of Link and Super Mario All-Stars, it's so cool to see the true flexibility of the MMC5.

I remember you also made a saving hack for Super Mario Bros. 3, I remember the last update (V7) sometimes didn't behave on cartridge, it would boot to a black screen. Still really awesome when it did work.

Offline infidelity

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Re: Question regarding the 512kb sram chips
« Reply #10 on: July 31, 2017, 01:07 AM »
Thanks for the kind remarks. :-)

I actually had to degrade my all-stars nes rom, so I could test the irq using a PowerPak CF flashcart. The irq worked fine....

It was then that I realized, that I needed to rewrite all my irq routines. Because an emulated mmc5, produces different results when using an authentic mmc5 cart.

A friend of mine took the liberty of creating a custom mmc5 dev cart out of Just Breed, and shipped it to me so I can test my games.

Right now everything is working great, I just need to fix up the Watership irq in world 8. So right now I have 2 versions, one for emulators, the other for authentic mmc5 mapper chips.

And regarding the save feature on Mario 3, it's pretty obsolete now, I just have others redirect themselves to my latest build of allstars nes. The sram routines I set up are much more reliable in that, then the standalone Mario 3. :-)

Offline KRIKzz

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Re: Question regarding the 512kb sram chips
« Reply #11 on: August 01, 2017, 02:31 PM »
Ok, the hardware aspect sounds like I could do on my end to modify the cartridge.

On the firmware end, would this be a difficult code to implement on your end? If it's not, would you be willing to make the nessecary additional code, so I could flash that to the N8 cartridge, and a schematic from where the additional wire needs to be soldered to, from the FPGA chip?

It will not be hard on firmware end. Extra address lines can be soldered to pin 22 and 27. Pin 22 should be unsoldered from PCB. But keep in mind that MMC5 implementation is far from the perfect, it enough to run castlevania, but most of other games does not work

Offline infidelity

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Re: Question regarding the 512kb sram chips
« Reply #12 on: August 01, 2017, 03:55 PM »
Thank you krikzz. Would you still be willing to make the proper modifications to the firmware, so I could test it out? If so. I'll be purchasing the N8 along with the replacement 1024kb chips asap.

So just that I'm understanding you, I need to have pin 22 lifted from the pcb, and have a wire attached to it, correct? And pin 27, I have a wire attached to that pin too correct? Now, where will those wires be coming from exactly, that are attached to the fpga 22 & 27 pins?

Is the firmware for mmc5 open source, or would you be willing to share the code? I may be able to find someone who could take the code further if need be.
« Last Edit: August 01, 2017, 04:05 PM by infidelity »

Offline KRIKzz

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Re: Question regarding the 512kb sram chips
« Reply #13 on: August 02, 2017, 01:05 PM »
You should connect pin 22 and 27 to upper address line on each 1024kb chip. Also you probably will need pullup resistor at pin 22, because it working as input at the moment, signal will float and you will have random address value on other mappers, which not controls this pin. I may share fpga code for MMC5, so you can make any changes. I could make address expansion changes for you, but i can't say when i will have time for that

Offline infidelity

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Re: Question regarding the 512kb sram chips
« Reply #14 on: August 02, 2017, 01:55 PM »
You should connect pin 22 and 27 to upper address line on each 1024kb chip.

Are you saying that pin 22 needs 2 wires going from it, to both prg and chr. And pin 27 needs 2 wires going from it, to both prg and chr?

Also, can you tell me the pin number on both the prg and chr that are the upper address lines?

Also you probably will need pullup resistor at pin 22, because it working as input at the moment, signal will float and you will have random address value on other mappers, which not controls this pin.

So the resistor near pin 22, I should remove it completely from the pcb?