~ OPENSOURCE USB CARTRIGE DEVELOPMENT ~

LocalH · Post by **LocalH** » Sat Jan 26, 2008 9:52 pm

8MB would be good for commercial ROM usage, 32MB would be useful for homebrew (imagine the possibilities for MD-only code if you have 64 pages of 512K available to you). It'd be nice to see emulators support this as well (unless there is already one that does, instead of supporting SSF2 only).

I know I keep repeating myself, but when I first read of how SSF2 banking works, and saw that it supported up to 64 pages while SSF2 only had 10, I dreamed of what would be possible when you could have that much storage available to you (and for MD-only code, 32MB is a shitload). Here we have the perfect opportunity to make such techniques available to the homebrew scene without each person having to make their own PCB (some of us are primarily software and don't have any knowledge when it comes to building hardware). Like I said, have two versions of the cart - one that's priced lower and supports up to 8MB, and a higher-cost one that supports the full 32MB (maybe even make the former upgradeable so that one could buy it, decide to upgrade, and then swap out a chip and throw a jumper).

Shiru · Post by **Shiru** » Sat Jan 26, 2008 10:35 pm

I don't understand why more memory could be useful for homebrew. Is there was at least one man, who work on homebrew project, but not finished it because run out of memory? Also, what useful can be stored in this additional memory? And, is that useful content can be actually created by homebrew developers? For now, only one commercial game (SSF) uses some additional memory, and I highly doubt that homebrew developers ever can create anything comparable with it.

Chilly Willy · Post by **Chilly Willy** » Sun Jan 27, 2008 12:00 am

Shiru wrote:I don't understand why more memory could be useful for homebrew. Is there was at least one man, who work on homebrew project, but not finished it because run out of memory? Also, what useful can be stored in this additional memory? And, is that useful content can be actually created by homebrew developers? For now, only one commercial game (SSF) uses some additional memory, and I highly doubt that homebrew developers ever can create anything comparable with it.

Why do you need RAM? Look at DOOM. The 32X is easily capable of playing DOOM (there is a cart form of it after all

). The problem with the cart version is that everything had to fit into the cart. Regular DOOM loads the level data/graphics/sounds/etc off the harddrive/CD into RAM. If you wish to have a regular version of DOOM for the 32X, you need two things: some kind of block drive to load the data from, and RAM to store the data into. With the SEGA CD, you have the needed block device. The problem is that DOOM needs a minimum of 2MB of RAM for the loaded data. You don't have that much RAM, even counting all the RAM in the Genesis, CD, and 32X.

So a cart that gave you 2MB or more of RAM (anything more than 4MB would need to be bank selected) plus an SD card interface would be perfect for bringing larger disc-loaded games to the Genesis/CD/32X.

Jorge Nuno · Post by **Jorge Nuno** » Sun Jan 27, 2008 12:06 am

If it is to be using DRAM like I suggested, then don't use DRAM

OMGLOL

Use SDRAM: just place a SDRAM socket in the cart and the user would place a SDRAM module (standart-184pin/3.3V)... Want a big storage? A 256Megabyte SDRAM dimm will probably be enough, if not overkill

Even a 64MB one is super common, any pc from 200MHz to 1GHz will have SDRAM in its mainboard

The downside is that probably it will be wasting data pins because sdram dimms have a data bus of 64bit, unless the FPGA multipexes them, but then the FPGA price will go to the sky...

Crap, I will be using EDO DRAM that I have... (32bit databus, wasting half of it)

tinctu · Post by **tinctu** » Sun Jan 27, 2008 12:11 am

This cartrige must be cheap!!!
So no CoreDUO + 256MB ram please

Jorge Nuno · Post by **Jorge Nuno** » Sun Jan 27, 2008 12:21 am

Forget about SRAM it's uber-expensive, but it's the best memory out in the market: unlimited rewrites, data retention with a small battery, fast access times, some draw very little power, the easiest type to interface aside from ROM. But with a density of Megabytes... just go for something else...

I still think SDRAM/DRAM EDO is the best..., you can even put a socket in the pcb and put any sized stick in it...

Core Duo BIGLOL, the megadrive doesn't need that, the 68000 eats Coreduos at breakfast...

Ummmm cheap cart + USB + FPGA + SRAM (to saves) + SD/MMC reader + Memory buffer... + + + ... naaaahhh it won't be cheap in this world

Shiru · Post by **Shiru** » Sun Jan 27, 2008 12:30 am

Chilly Willy wrote:Why do you need RAM?

I thought, we speak about cart for SMD, so it's RAM buffer acts as ROM from SMD side.

Jorge Nuno · Post by **Jorge Nuno** » Sun Jan 27, 2008 12:30 am

Shiru wrote:
Chilly Willy wrote:Why do you need RAM?
I thought, we speak about cart for SMD, so it's RAM buffer acts as ROM from SMD side.

Exactly but what RAM type? tinctu has an unknown problem with SDRAMs...

tinctu · Post by **tinctu** » Sun Jan 27, 2008 12:30 am

But maybe some old
16/32mb EDORAM + battery from 486 will be not BAD...
Idea...

Case will be little bigger but that is OK...

Well there are lot of PC Second Hands... that is right.

Jorge Nuno · Post by **Jorge Nuno** » Sun Jan 27, 2008 12:32 am

tinctu wrote:But maybe some old 16/32mb EDORAM + battery from 486 will be not BAD...
Idea...
Well there are lot of PC Second Hands... that is right.

Yup there is where you are getting those RAMs and they are good enough for the MD

tinctu · Post by **tinctu** » Sun Jan 27, 2008 12:36 am

But will be cartriges compatible /different RAM modules.../???
I mean for some kind of firmware...

tinctu · Post by **tinctu** » Sun Jan 27, 2008 12:38 am

BTW I was thinking about max. price -> 50USD-max 70USD (I mean all electronic parts) not more...

Jorge Nuno · Post by **Jorge Nuno** » Sun Jan 27, 2008 12:38 am

The FPGA could detect the memory available... just wire all the addresses to the DRAM socket, the FPGA would do the dirty work of detecting how much ram the cart has installed...

A firmaware!? Of course a native 68K program to browse trough the card filesystem and load the desired ROM to RAM...

BTW is there any commercial device with theese features?

tinctu · Post by **tinctu** » Sun Jan 27, 2008 12:45 am

OK so looks like we will have 2 versions ->

1./ HOMEBREW CARTRIGE (small 2-16MB DATA RAM)
2./ DEVELOPMENT CARTRIGE (min. 32MB DATA RAM)

Who is for Battery-EDO RAM SLOTS??? + SD/CF...
Who is for some kind of RAM for DATA / Battery-RAM??? + SD/CF...

Vote please?

Or small RAM 2MB+EDO SLOT for expansion

???

PS:But remember -> I want do only cartrige for homebrew apps + demos + music... /4-32mb is enough for me... + SD or whatever "memory card".../

Jorge Nuno · Post by **Jorge Nuno** » Sun Jan 27, 2008 12:46 am

Why do you want a SRAM version? If it is to be using DRAM EDO then why use SRAM? somekind of RAM !? There are only a few types:

DDR III/II/I -> nahhh, don't even look at it;
PSRAM -> Where to buy these?;
SRAM -> Too expensive;
DRAM EDO -> Good as long as there are old pcs around
SDRAM Dimm -> Good, but requires many wires or trash 75% of the data bus
FRAM/NVRAM ->nonvolatile RAM? Sell your car to buy a 64K of these

FLASH -> its not RAM but could be a solution: has endurance problems, and it is required to erase an entire data block to write a single byte...