Date   : Fri, 12 Jun 1992 09:40:22 BST
From   : RWF Whitehand <R.W.F.Whitehand1@...>
Subject: SWR

[Extracted from a large message from Martin Ebourne, Challenger's co-sysop]

>      
>     Re: The S-RAM problem (You can quote this if you like): 
>      
>     Yes, you are quite right about the notCS and the diode arrangement. It 
> must have been late at night, I wasn't thinking! I did precisely the same as 
> that, only I used a 1M resistor. Thanks for pointing it out. I have actually 
> tried both my RAM designs (the 2 socket one was my first before I found the 
> rom latch as well, although I did have a ROM board then so I couldn't have 
> used it anyway), and they both work perfectly (when wired correctly!). It is 
> also fairly easy to wire a switch or two for read/write protect. 
>      
>     Something I didn't try, but was thinking about, was battery backup. That 
> wouldn't be hard if you had one of the low voltage-current standby RAMs which 
> could run on 3V. All you would need is a couple of diodes to the Vcc pin 
> (probably germanium for low voltage drop), a couple of Duracell and there you 
> have an instant battery backup! I'm not sure whether you would get any 
> corruption in the ram on power up/down, but you may be able to wire the notWE 
> line into the battery as well, which would protect it. If anyone's 
> adventurous, I would be interested to know! Read protect it definately a good 
> idea with battery backup though, in case of corruption. 
>      
>     I now have a Solidisk 256k board which can take 32k EPROMS with a special 
> ROM store facility to select them. In attempt to save having to by 32k EPROMS, 
> I soldered my collection into about 5-6 pairs, each with an EPROM directly on 
> top of another, and the chip select lines taken away to the board. 
> Unfortunately, they were all NMOS, and so consequently they got extremely hot 
> in use (since there was no air flow around the bottom one). I had to abandon 
> that idea, and very few of them survived the desoldering and chip select pin 
> bending back process. RIP. I now have quite a few 32k EPROMS!! 
>      
>     Right. You can stop quoting now!!! 
>      

Regards,

Richard.

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 SysOp: Richard Whitehand - R.W.F.Whitehand1@...
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