Date   : Fri, 08 Mar 1985 21:17:55 GMT
From   : Keith Doyle <keithd%cadovax.uucp@BRL-TGR.ARPA>
Subject: Re: Dynamic Memory

[............]
> I tried to install dynamic memory in my CompuPro system (8085/8088). The
> board could be strapped for up to 8 wait states so I didn't think that
> I would have any problems. I figured that in the worst case 8 wait states
> would be alright since the memory was so cheap. Wrong! I put the memory
> at 0000H and I couldn't get the 8085 to boot under CP/M since the disk 
> controller (DISK1) was too fast for the memory even with 8 wait states. 
> I put the memory above my RAM16's and tried to use the 8088 (CP/M86) 
> debugger to deposit values in the memory without any luck. The only way
> I could get the memory to work was to run my 8085 at 2 MHZ with no wait
> states. 
> 
> The lesson to be learned is that if you have a disk controller that
> does DMA don't buy dynamic memory. 
> 
> Dennis    [BRAKE@ARI-HQ1]

I have a CompuPro Disk1 that I've been using with an ExpandoRam dynamic
card for years!  The only problem I've ever had with the dynamic RAM card
was in conjunction with an el-cheapo Z-80 CPU card which I believe was
solvable, but I decided to scratch the CPU card anyway.  How fast is the
RAM supposed to be?  is it only 2 MHZ?  I would think that the DMA
speed would be somewhat governed by the rate it's coming off the disk
which ain't that fast.  Are you sure that speed is the problem?  If
by some chance the DMA is being clocked with the CPU's clock, maybe
something can be done to use a divided by 2 clock for the DMA.  However
before attempting something like this, I'd make sure that you really have
your finger on the problem.

Keith Doyle
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