Date   : Thu, 07 Mar 1985 17:10:42 GMT
From   : Chuck McManis <cem%intelca.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]

Which board was strapped to 8 wait states? If it was your memory the next
question becomes does the disk-1 even recognize waitstates on the bus?
An acquaintence at one of the local computer clubs spent a long time
developing a set of PALs (Programmable Array Logic) that could fully implement
the IEEE TMA (DMA to the rest of the world) spec that did take into account
external ready from the destination or source memory addresses. If done in
individual chips the circuit would have been quite large (he estimates 15 to
20 packages)

I have heard that the problems with Dynamic Ram and DMA were one of the most 
hotly debated subjects at the IEEE-696 meetings. And the end result was a 
workable solution but not many DRAM boards at the time met them. 

--Chuck
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