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starhawk1426459861

Noob here, looking for education (in all the wrong places?)

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OK, been in contact with the guy who did this, and he has been extremely patient with me and extremely helpful to me.

 

I'll be implementing a version of his emulator for this project... and using rather similar hardware. It seems that SPI SRAM is a bit expensive after all -- I was converting kB to MB in my head for no apparent reason -- and can't be used anyways. Linux only supports "directly accessible" memory -- that is, parallel-address RAM.

 

Among other things, Mr. Grinberg pointed me to a website that is selling 16mb 30pin SIMMs -- the largest size of that (antique) RAM that can be made due to pinout limitations. They're cheap!

 

So here's what I'll be looking at...

Storage + Swap -- SD card w/ swapfile + OS + data

RAM -- 16mb 30pin SIMM (60ns access time, wheeeee!)

Video out -- TBD... but it probably won't be color...

 

Interesting project in the link.

Interesting that the bottleneck on his system was CPU, with a faster processor it will be interesting to see where bottleneck is.

Using an ARM to emulate an ARM should make the emulator easier. (Of course you could emulate some other processor

that runs Linux ;-).

 

Since you are using an emulator no technical reason couldn't use SPI SRAM. (Linux on the emulated machine doesn't care.)

Wonder if one could use part of a higher density RAM module (e.g. part of 72 pin RAM.)

I have a bag of old SMART 2MB SRAM modules - too many pins to use the whole thing. But if you could find some obsolete (therefore inexpensive) memory module that uses higher density SRAM.

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@Igor: I'd rather spend $10 and get 16mb RAM than mess with those dinky SRAM chips. The real problem was that I stupidly thought 16k*8 was 128M not 128k. I feel like an idiot for that one -- and rightly so!

 

@abecedarian: looks like those chips are not sold anymore, and quite honestly it's far easier for me to borrow someone else's work that gets me 90% of the way and get the rest of the way on my own. With Blondihacks' circuit, all I have to do is figure out how to interface it to something 4 times the speed. (The Atmel chip she has is 20mhz and the Stellaris chip is 80mhz.) I'll probably also have to do some slight adjusting as Blondihacks uses a -PA chip which has been discontinued and I'll have to use the -PU chip. Not sure what the differences are, but I'll probably find that out pretty quickly.

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They are available on ebay.

Anyhow, I only mentioned it because it has a comparatively simple interface: 8 data lines, a few control wires and an interrupt line.

The 9918 and derivatives were used on the TI-99/4a, MSX computers, and a few console gaming systems... I believe Sega used it on one.

On some computers, the CPU didn't have any attached ram and used the video ram to store programs and variables.

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