Memory/cache on the 11/70

Dave McGuire mcguire at
Wed Dec 31 12:31:44 CST 2008

On Dec 31, 2008, at 1:26 PM, bfranchuk at wrote:
>> As far as pricing goes, a 4 layer board (you *really* want at  
>> least 4 layers here) + components + assembly & test should be <  
>> $1000.  How much less I don't know.  The target for my unibus  
>> memory board is ~$500 (fully assembled & tested + some profit).   
>> Given that this wouldn't need unibus transceivers (hideously  
>> expensive when you can find them) I would expect this to be in the  
>> same ball park especially if it can be contained on a quad board.
>> The other issue with not replacing the cache, is that the verilog  
>> to implement this would *much* simpler (ie it can probably be  
>> completed faster).
> TTL ... and a few gals... I trust hardware more than software is my  
> view point.
> Real cache memory   32k*8 is about 15ns access time in a skinny 28  
> pin package.
> I am just not sure how much memory you can get on a card  
> however ... Sigh.

   Just don't use "PC motherboard SRAMs" as someone suggested  
earlier.  They're nowhere near as easy to find as some people think  
they are, at least for some of us...I trashed all of my 486 boards a  
decade ago.  Standard, currently-available SRAMs are cheap and easy  
to work with, and are just as fast.  I have a few 512KB SRAMs in  
SOJ-36 packages sitting on the bench right now; I think they were  
about $7/ea in small quantities from a distributor.


Dave McGuire
Port Charlotte, FL

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