Mapper 472 / NROM-383 and NROM-368

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akerasoft
Posts: 10
Joined: Thu May 11, 2023 8:50 am

Mapper 472 / NROM-383 and NROM-368

Post by akerasoft »

** Update Mapper number changed to 474. Also sample ROMs with hello world. (Previous suggested mapper number was 472).

I've created a mapper that maps 0x4020 to 0xFFFF to PRG ROM.
I called it Akerasoft Mapper 474.
It maps more than NROM-368. But an NROM-368 is also planned. So the original one is NROM-383 (rounding down).

My prototype uses FLASH memory but is designed to be programmed before soldering and is not reflashable.

https://www.nesdev.org/wiki/NROM-368

My design however is this 64KB of ROM space:
Bank 0:
Memory 0x0000 - 0x3FFF (empty or ignored, all zeros?)
Bank 1:
Memory 0x4000 - 0x401F (empty or ignored, all zeros?)
Memory 0x4020 - 0x7FFF (PRG)
Bank 2:
Memory 0x8000 - 0xBFFF (PRG)
Bank 3:
Memory 0xC000 - 0xFFFF (PRG)

Mapper 472 submapper 0 - 0x4020 - 0xFFFF (NROM-383)
Repo: https://github.com/Akerasoft/AS_Mapper_474
Schematic: https://github.com/Akerasoft/AS_Mapper_ ... ematic.pdf

Mapper 472 submapper 1 - 0x4800 - 0xFFFF (NROM-368)
Repo: https://github.com/Akerasoft/AS-NROM-368
Schematic: https://github.com/Akerasoft/AS-NROM-36 ... ematic.pdf

For .NES File my design is this 48KB of ROM space:
Bank 0:
Memory 0x4000 - 0x401F (empty or ignored, all zeros?)
Memory 0x4020 - 0x7FFF (PRG)
Bank 1:
Memory 0x8000 - 0xBFFF (PRG)
Bank 2:
Memory 0xC000 - 0xFFFF (PRG)
hello_world_nrom_383.nes
Hello World - Mapper 474 - Submapper 0 sample - NROM-383
(56.02 KiB) Downloaded 19 times
hello_world_nrom_368.nes
Hello World - Mapper 474 - Submapper 1 sample - NROM-368
(56.02 KiB) Downloaded 17 times
Repos for the above built ROMs:
https://github.com/Akerasoft/hello_world_nrom_383
https://github.com/Akerasoft/hello_world_nrom_368

Code: Select all

|--------|-----------|---------------|--------|----------------|----------|----------|-----------|-----------|
| Mapper | Submapper | Mapper Type   | Save   | Save Type      | ROM Size | RAM Size | ROM Start | RAM Start |
|--------|-----------|---------------|--------|----------------|----------|----------|-----------|-----------|
| 474    | 0         | NROM-383      | N      | None           | ~48KB    | None     | 0x4020    | N/A       |
|--------|-----------|---------------|--------|----------------|----------|----------|-----------|-----------|
| 474    | 1         | NROM-368      | N      | None           | 46KB     | None     | 0x4800    | N/A       |
|--------|-----------|---------------|--------|----------------|----------|----------|-----------|-----------|
| 474    | 2         | NROM-320      | N      | None           | 40KB     | None     | 0x6000    | N/A       |
|--------|-----------|---------------|--------|----------------|----------|----------|-----------|-----------|
| 474    | 3         | NROM-320-SB   | Y      | SRAM + Battery | 40KB     | ~8KB     | 0x6000    | 0x4020    |
|--------|-----------|---------------|--------|----------------|----------|----------|-----------|-----------|
| 474    | 3         | NROM-320-SF   | Y      | FRAM AKA FeRAM | 40KB     | ~8KB     | 0x6000    | 0x4020    |
|--------|-----------|---------------|--------|----------------|----------|----------|-----------|-----------|
For mapper 474 submapper #2 without saving
ROM is from 0x6000 to 0xFFFF.

For mapper 474 submapper #3 with saving...
Save RAM is from 0x4020 to 0x5FFF
ROM is from 0x6000 to 0xFFFF.

FRAM also called FeRAM is a special type of non-volatile memory that is as fast as SRAM but does not need a battery to be non-volatile.
It is more expensive than SRAM. It is also RAM because it can be accessed randomly for both read and write just like SRAM.
Last edited by akerasoft on Mon Sep 04, 2023 2:51 pm, edited 9 times in total.
User avatar
aquasnake
Posts: 515
Joined: Fri Sep 13, 2019 11:22 pm

Re: Mapper 472 / NROM-383 and NROM-368

Post by aquasnake »

Most coders are detached from reality because they only have software thinking rather than hardware thinking.

For you, $4020- $FFFF appears to have a wider addressing range than $4800- $FFFF. However, in actual design, the former requires a 16 bit numerical comparator, while the latter only requires A [11.. 15] as inputs to a chip of quad-NAND gates.

Therefore, you would understand why only NROM-368 is meaningful to implement NROM rather than over 368Kbits
akerasoft
Posts: 10
Joined: Thu May 11, 2023 8:50 am

Re: Mapper 472 / NROM-383 and NROM-368

Post by akerasoft »

Actually. Both designs use an OR gate.
NROM-383 (uses 8 input OR gate, plus an extra 2 input Or gate).
NROM-368 (uses 4 input OR gate)

I tried to think about the comparator. I was not sure if that would actually work.
NewRisingSun
Posts: 1510
Joined: Thu May 19, 2005 11:30 am

Re: Mapper 472 / NROM-383 and NROM-368

Post by NewRisingSun »

Can you make it mapper 474, please? I have assigned mapper 472 and 473 for some multicart mappers already, but failed to update the wiki in time. :oops:
akerasoft
Posts: 10
Joined: Thu May 11, 2023 8:50 am

Re: Mapper 472 / NROM-383 and NROM-368

Post by akerasoft »

Sure, it can be Mapper 474. Can the wiki be updated so that I don't have to change the number again?
NewRisingSun
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Joined: Thu May 19, 2005 11:30 am

Re: Mapper 472 / NROM-383 and NROM-368

Post by NewRisingSun »

done
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aquasnake
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Re: Mapper 472 / NROM-383 and NROM-368

Post by aquasnake »

akerasoft wrote: Thu May 11, 2023 12:17 pm Actually. Both designs use an OR gate.
NROM-383 (uses 8 input OR gate, plus an extra 2 input Or gate).
NROM-368 (uses 4 input OR gate)

I tried to think about the comparator. I was not sure if that would actually work.
8 input OR gate is 5 times the price of quad 2-input NAND

Comparator has better versatility, but is rarer and more expensive in the market
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Fisher
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Re: Mapper 472 / NROM-383 and NROM-368

Post by Fisher »

aquasnake wrote: Thu May 11, 2023 7:13 pm 8 input OR gate is 5 times the price of quad 2-input NAND

Comparator has better versatility, but is rarer and more expensive in the market
Can't this be made with 8 diodes and a resistor?
If so, would that be cheaper?
akerasoft
Posts: 10
Joined: Thu May 11, 2023 8:50 am

Re: Mapper 472 / NROM-383 and NROM-368

Post by akerasoft »

.NES File Format - Mapper 474.
8 KB CHR
48KB PRG (3 banks)
Bank 0 - 0x4020 or 0x4800 to 0x7FFF (prepadded with zero's)
Bank 1 - 0x8000 to 0xBFFF
Bank 2 - 0xC000 to 0xFFFF

To make ROM bin files from NES file or make NES file from ROM bin files.
https://github.com/Akerasoft/Mapper474ROMTool

To resize an NROM to Mapper474
https://github.com/Akerasoft/NROMToMapper474

After having a Mapper474 .NES file you can HEX edit.
akerasoft
Posts: 10
Joined: Thu May 11, 2023 8:50 am

Re: Mapper 472 / NROM-383 and NROM-368

Post by akerasoft »

Fisher wrote: Sat May 13, 2023 11:18 am
aquasnake wrote: Thu May 11, 2023 7:13 pm 8 input OR gate is 5 times the price of quad 2-input NAND

Comparator has better versatility, but is rarer and more expensive in the market
Can't this be made with 8 diodes and a resistor?
If so, would that be cheaper?
It would be 9 diodes. Not sure about the price.
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aquasnake
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Joined: Fri Sep 13, 2019 11:22 pm

Re: Mapper 472 / NROM-383 and NROM-368

Post by aquasnake »

9 diodes can gate $4020-$403F, but I'm not sure if they can gate >=$4020
akerasoft
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Joined: Thu May 11, 2023 8:50 am

Re: Mapper 472 / NROM-383 and NROM-368

Post by akerasoft »

aquasnake wrote: Wed May 24, 2023 11:19 pm 9 diodes can gate $4020-$403F, but I'm not sure if they can gate >=$4020
An AND gate is used for >=$4000, adding (a 9 input or gate) or 9 diodes changes it to >=$4020.
akerasoft
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Joined: Thu May 11, 2023 8:50 am

Re: Mapper 472 / NROM-383 and NROM-368

Post by akerasoft »

Update: ROMs and Repos for the sample ROMS was added.
akerasoft
Posts: 10
Joined: Thu May 11, 2023 8:50 am

Re: Mapper 472 / NROM-383 and NROM-368

Post by akerasoft »

Added NROM-368 repo and schematic.

Mapper 472 submapper 1 - 0x4800 - 0xFFFF (NROM-368)
Repo: https://github.com/Akerasoft/AS-NROM-368
Schematic: https://github.com/Akerasoft/AS-NROM-36 ... ematic.pdf
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