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designing a replacement memory controller w/ memory

I have a 68030 accelerator card that connects to an optional RAM expansion card. I'd like to design a compatible larger memory expansion card. This memory card contains an onboard DRAM memory controller made by QLogic. I can hopefully reverse engineer the pinouts for the connectors (two 50-pin header connectors) between the accelerator card and the RAM expansion card by tracing. I have a smaller capacity card for comparison.

I'm thinking of using a small FPGA board with SRAM memory, but I'm open to other ideas. The requirements are:

32-bits wide data 8MB ram. 60-80ns response time Easy to source components in low quantities in the US Relatively easy to implement (i'm trying KISS here) low(er)-cost (no profit potential here)

I'm guessing that the addresses that will appear on the address bus will be arriving to my replacement memory controller shifted (is the word mapped?) to some particular range, and that I'll need some type of lookup table to map those addresses to 0-based address bits on the memory itself. Right?

Is this plan reasonable? The software that configures the OS for the memory can be setup to accept 8 megs, so I'm not horribly worried yet about how the OS-side of things is going to be handled.

Thanks

Keith

Reply to
Keith M
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Check voltage levels on modern parts, eh? There's a lot of low voltage stuff these days. Also look into pseudo-static RAM, it is self-refreshing DRAM that looks like a SRAM. Modern parts do come in BGA packages though, less friendly for the hobbyist.

Reply to
a7yvm109gf5d1

Good idea. Is most stuff 3.3v now? I've seen "5v tolerant" listed before on low voltage parts.

Any downside like lack of speed or anything?

Yuck. If I'm serious about this I'm going to have to get used to higher density parts because I'm going to be dealing with a minimum of

24 address and 32 data pins, so 56 pins w/o control leads, etc. I've considered schmartboards for breaking some of that stuff out. I've never made my own custom pcb, perhaps this will be the first.

I'd love to find an FGPA with either built-in ram, or a small reasonably-priced eval board that includes the ram (and hence likely supported with a free ram controller ip core) and a header for 60-70 pins.

Prototyping high pin count stuff though seems difficult for the hobbyist.

Thanks

Keith

Reply to
Keith M

3.3V is a relatively high voltage these days.

Not for a 68030 I think.

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I wonder if there's a market for packaging modern parts onto a PCB for hobbyists. Sounds like a plan.

But not impossible. If you make a PCB with soldermask and use ministencils with solderpaste, you can reflow in a toaster oven.

Reply to
a7yvm109gf5d1

Scope error. OP is not talking about 8 GB of ram but 8 MB of ram.

Reply to
JosephKK

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