1 Jun
1999
1 Jun
'99
11:43 a.m.
I have some DRAM boards that I've used with my
Poly88.
These are 64K boards and I thought I'd use them but the disk's
DMA doesn't seem to write to them. I'm able to read and write
from the front toggles, just not from the DMA to the RAM.
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.
Welcome to the world of S-100, where DRAM boards often didn't
support DMA controllers properly. In some cases, you can rejumper
them so that the DMA vs refresh timing conflict isn't such a problem.
But many of us just went to pure static RAM systems where DMA
was being done.
What disk controller are you using, BTW? In some cases the problem
isn't so much the memory, but it's the disk controller.
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.
It certainly is a major milestone. Congratulations!
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
1 Jun
1 Jun
11:58 a.m.
CLASSICCMP(a)trailing-edge.com wrote:
--snip--
Welcome to the world of S-100, where DRAM boards often didn't
support DMA controllers properly. In some cases, you can rejumper
them so that the DMA vs refresh timing conflict isn't such a problem.
But many of us just went to pure static RAM systems where DMA
was being done.
What disk controller are you using, BTW? In some cases the problem
isn't so much the memory, but it's the disk controller.
Hi
It is an old descrete TTL controller by Digital Sytems. It
has a seperate bus interface card labled "HB-1". The controller
in the disk drive box is a "FDC-1". I have schematics for both,
so I may be able to do something. I may just have to continue
with the statics but these boards are quite old and I've
already had to replace one 74LS32 on one of the boards. Maybe
I should write a more intense RAM test and run them through
their paces. I don't think I'd want to wait for GALPAT but
a simple March C seems to be in order.
Dwight
8:33 p.m.
New subject: Corona luggable, 1302 drive
I found a curious computer, and sorry to those I asked many dumb questions
of without looking closer at the computer. It is a rather tall luggable
(sort of like the osborn or kaypro), and the brand is a Corona. Green
screen on the left, perhaps a fan grille with a contrast knob at the
bottom, and a couple 5.25 floppies on the right (one slot missing
currently). Any interest?
Also a couple old hard drives, both 5.25 half height, one has in pencil
model 1302 18 mb, the other nothing. Same connector, two sets of edge
fingers with a slot cut in them, one set is maybe 9 conductors per side,
the other maybe 25.
The Masspar, a model 2204, I was told has 9 ESDI 1.3 GB drives, and is
still intact as of today with manuals and a dec PC of some kind.
8:43 p.m.
New subject: Corona luggable, 1302 drive
Mike Ford wrote:
I found a curious computer, and sorry to those I asked many dumb questions
of without looking closer at the computer. It is a rather tall luggable
(sort of like the osborn or kaypro), and the brand is a Corona. Green
screen on the left, perhaps a fan grille with a contrast knob at the
bottom, and a couple 5.25 floppies on the right (one slot missing
currently). Any interest?
No interest here, but it sounds like the PC-400 and that was the first IBM
type of computer I used. Corona later became Cordata. IIRC, it was limited
to 512K of RAM unless an expansion board was used.
9158
days inactive
9159
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3 comments
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participants (4)
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CLASSICCMP＠trailing-edge.com -
elvey＠hal.com -
marvin＠rain.org -
mikeford＠netwiz.net