More Bringing up a CPM

From: allisonp_at_world.std.com <(allisonp_at_world.std.com)>
Date: Tue Jun 1 15:54:42 1999

> I've had some issues with RAM loosing data but I not sure
> where the problem is yet. This may be my problem. The
> RAM boards I have are some older 4K, 8K and one 16K
> static RAM boards that make up the needed 64K ( actually
> 62K ) by the CPM.SYS file I have.

If static ram is loosing data you likely have a bus noise or other timing
problem. If your running a 4mhz z80 try running with 1 waitstate on
memory accesses, some of those old boards didn't do 4MHz. If your running
an 8080 many of the dram card didn't work well with oder 8080 designs.
Some like the Vector 48k, will not run at all as they require ta z80 for
correct refresh..

> Does anyone know what the problem is here? Is there some
> timing or pin out issue with DRAMs that would cause this
> to happen in a standard IMSAI 8080? I'd really like to use
> this DRAM because I trust it more than the statics in the
> system, at least until I get things fully functional.

For those old systems DRAM was the lest reliable generally and most
statics tended to work ok. DMA... you sure that card is a DMA, very few
were. Most of the older systems were totally incompatable to barely
compatable with DMA devices and bus termination for those is a must have.

> In any case, I think just getting to the A> prompt is
> a major mile stone. I had to completely write a boot loader,
> CBIOS, disk formatter and serial data transfer to get this far.

yes it is. You have some basic hardware reliability issues to deal with
yet and likely bus noise is one of them. The IMSAI was far better than
the Altair but like most of the older s100 crates terminating the bus was
not a bad thing and sometimes required for reliable operation.

Allison
Received on Tue Jun 01 1999 - 15:54:42 BST