custom co-processor chips like the SVP?

For anything related to cart (SRAM, SF2 mapper, audio, CD mode 1, ...)

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djcouchycouch
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Post by djcouchycouch » Wed Oct 17, 2012 6:05 pm

Charles MacDonald wrote: Unless you take the 32X route, but that's another story. :D
Having a cart with its own AV in/out would be weird but interesting. Or a shrunk down 32X in cart form.

If you're adding custom AV ports to the cart, might as well be HDMI :)

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Post by Chilly Willy » Wed Oct 17, 2012 6:44 pm

Charles MacDonald wrote:
Chilly Willy wrote:Yes, the MegaEverdrive is a good FPGA cart, but like I said, it requires programming at the gate level. I should probably get one myself.
There are also a lot of "macro" designs for bigger components like CPUs and peripheral chips you can use, with minimal glue logic to tie them together. Check out opencores.org to get a taste of what's available.
I'm quite familiar with opencores, but you still have to merge whatever you want with the base MED design or you'll lose the ability to use it on the MD. So you at least have to be good enough with VHDL, or whatever is used, to merge two existing designs together into one working whole.

I also wonder which Cyclone II is used... how many gates does it have, and how many are left for other uses? Should probably ask KRIKzz about that.
Hey which SH2 is available at Digikey? I couldn't find anything. I love the SH series but it seems impossible to find anything for sale at decent prices/volumes these days.
Everything from the 7010 to the 7780. Just go to parts search, enter "superh", and you'll get 370 matches. Click the "in stock" button and search again and you'll get 94 matches.

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Post by doragasu » Fri Oct 19, 2012 3:51 pm

If you only want to do maths, ¿why to use an FPGA? ¿why not to use a DSP?

DSPs are cheaper, easier to use, can be programmed using C/C++, can do maths a lot better than FPGAs costing the same and don't require knowledge in VHDL/Verilog.

FPGAs would make sense if you would need very high speed I/O (like for example HDMI output), but to do maths, I think DSPs are a better approach.

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Post by djcouchycouch » Fri Oct 19, 2012 4:09 pm

doragasu wrote:If you only want to do maths, ¿why to use an FPGA? ¿why not to use a DSP?

DSPs are cheaper, easier to use, can be programmed using C/C++, can do maths a lot better than FPGAs costing the same and don't require knowledge in VHDL/Verilog.

FPGAs would make sense if you would need very high speed I/O (like for example HDMI output), but to do maths, I think DSPs are a better approach.
DSPs are definitely an option. We're just dreaming about this so anything goes :)

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Post by Chilly Willy » Fri Oct 19, 2012 4:47 pm

Also, the FPGA option already exists if you don't mind shelling out $150 for a MegaEverdrive. That's the primary problem with the MED - not many people will spend that kind of money on a cart for an old console. It needs to be more like the EverdriveMD - less than $80. Ideally, to get the best market penetration, it needs to be as low cost as possible while still providing the features needed.

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Post by doragasu » Fri Oct 19, 2012 6:17 pm

I have a lot of experience developing systems with Texas Instruments DSPs, both fixed and floating point. Unfortunately, I'm almost new to Megadrive scene and I have near to no spare time. But definitely, I'd love to develop a DSP enabled cartridge if someone was willing to use it.

BTW, does the Megadrive have an audio analog input in the cartridge port? I don't remember having seen the pins when I had a look to the cartridge pinout. A DSP would be extremely useful also to improve music and sfx.

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Post by Chilly Willy » Fri Oct 19, 2012 6:45 pm

doragasu wrote:I have a lot of experience developing systems with Texas Instruments DSPs, both fixed and floating point. Unfortunately, I'm almost new to Megadrive scene and I have near to no spare time. But definitely, I'd love to develop a DSP enabled cartridge if someone was willing to use it.

BTW, does the Megadrive have an audio analog input in the cartridge port? I don't remember having seen the pins when I had a look to the cartridge pinout. A DSP would be extremely useful also to improve music and sfx.
Yes, there are both left and right audio inputs from the cart port. That's what the 32X uses for audio. It was assumed at first that Virtua Racing MD also connected to those lines, which would make some sense since the SVP is just a 16-bit Samsung DSP. However, the VR carts I've seen don't use those audio lines.

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Post by haroldoop » Sat Oct 20, 2012 12:45 am

Slightly crazy suggestion: how about Arduino integration? It could open the doors for some cool hardware hacks.

Charles MacDonald
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Post by Charles MacDonald » Sat Oct 20, 2012 12:47 am

doragasu wrote:I have a lot of experience developing systems with Texas Instruments DSPs, both fixed and floating point. Unfortunately, I'm almost new to Megadrive scene and I have near to no spare time. But definitely, I'd love to develop a DSP enabled cartridge if someone was willing to use it.
Are there any DSPs you think would be a particularly good fit with the Megadrive?

They are old parts, but I've looked at the ADSP-2100 series and TMS320CX series in the past. Wondering if there is anything better that is 5V and still comes in a small package (easier to hand-assemble).

Of course there's nothing wrong with hooking up a more modern DSP too. :)

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Post by doragasu » Sat Oct 20, 2012 11:22 am

Finding a good 5V DSP will not be easy. The only 5V ones that comes to my mind right now, are some dsPICs, and C2000 ones. I don't think using one of these is worth the effort.

I assume we only need fixed point maths. Maybe a TMS320VC5501/5502 would be a good fit. They are available in QFP packages and can compute up to 600 MMACs per second. The only problem is they are 3.3V.

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Post by TmEE co.(TM) » Sat Oct 20, 2012 1:57 pm

3.3V is not really a problem, all flashes are that anyway and getting around it is not so hard.
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Post by Chilly Willy » Sat Oct 20, 2012 6:00 pm

Some of the SuperH chips still run at 4 to 5.5 V. Don't limit yourself to pure DSPs or you may neglect something better. A pure DSP is also harder for most programmers to use... it pretty rare that DSP architectures are covered in computer science classes.

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Post by doragasu » Sat Oct 20, 2012 7:33 pm

TI DSPs are really easy to use. They can be coded using C/C++ and there are free libraries available to use their peripherals. You'll need to learn assembly language if you want to extract all the juice of the DSPs, but I suppose C is enough for most tasks.

It would be useful to know an estimation about the MIPS/MFLOPS and the amount of RAM required for the processor.

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Post by Chilly Willy » Sat Oct 20, 2012 8:07 pm

doragasu wrote:TI DSPs are really easy to use. They can be coded using C/C++ and there are free libraries available to use their peripherals. You'll need to learn assembly language if you want to extract all the juice of the DSPs, but I suppose C is enough for most tasks.

It would be useful to know an estimation about the MIPS/MFLOPS and the amount of RAM required for the processor.
Yeah, I suppose the TI DSP isn't too bad... it at least has decent tools available. I imagine you'd use something like this - it uses an external rom and has 128KB of internal ram. It also uses a flat package instead of the more common (and harder to solder) BGA package.

$14 in single unit quantities from DigiKey isn't bad as far as price goes. That's the cheapest external rom TMS DSP DigiKey carries. They have cheaper DSPs, but they're all internal rom. I need to get a few datasheets on them... I assume those are programmable roms, not mask roms?

Or maybe you were thinking something like this? This one is more like the SVP... a 16-bit DSP with not much else. It is 5V, though, which might make it easier to work with.

Looking at the SuperH chips, you have this and this. The first has a 16-bit external bus, while the latter has a 32-bit bus. Oddly enough, the 32-bit bus part is cheaper. Both are romless and have 8KB of internal RAM.

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Post by TmEE co.(TM) » Sun Oct 21, 2012 6:49 am

They have internal bootleader that loads in a program from external ROM or RAM. When you pay lots of money Ti can make you a custom internal ROM
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