29 Jun
2001
29 Jun
'01
3:48 a.m.
I've not used them myself, But a friend wirewraped
some custom unibus D/As. He used 4000 series CMOS
parts (4049/69 ?) or the tristate equivalents. I don't know
about the drive capability of those parts - I'd suggest
LS240/244s. Alternately you could use a DR11 or QBUS
equivalent (I think it has NPR dma), if 16 bits in, 16 bits
out are enough to run an IDE drive.
Regards,
Heinz Wolter
----- Original Message -----
From: "Jerome Fine" <jhfine(a)idirect.com>
To: <classiccmp(a)classiccmp.org>
Sent: Friday, June 29, 2001 9:11 AM
Subject: Re: Unibus / Qbus bus drivers and receivers
Michael
Davidson wrote:
Yes, I thought that a 74LS240 might be OK as a
bus receiver so
this sounds plausible. Of course I could always just use 8641's
for everything but this would probably push the chip count up a
bit and right now it's looking as if space will be quite tight
on the particular prototype board that I'm thinking of using.
Jerome Fine replies:
I have been following this thread since your first post yesterday.
What you seem to have omitted is the target interface. Maybe
I am missing something, but is your target a serial port like a
DL(V)11 or a disk interface - possibly raw SCSI (or now likely
MSCP may be allowed since I understand that the patents
expire this year)?
From my point of view, the other side of the fence is the software
device drivers that will be required. If the Unibus/Qbus module
emulates an existing DEC board, then there will already be software
available to use it.
In the past there has been some talk of a Qbus host adapter for
both SCSI and IDE drivers which emulates MSCP. I don't know
if Mentec acquired the rights to the MSCP patents, but if not
then Compaq is not likely to care at this point and in any case
if the patents for MSCP have expired, then there won't be a problem.
By the way, if IDE drives are used, the idea was to place the drives
right on the board since the 18" cable length limitation for a PC
environment is likely to be exceeded in a Qbus enclosure.
Just some thoughts which may be worth the cost of my time to
write this?
Sincerely yours,
Jerome Fine