A brief review of the problem:

GIVEN:
 Q-bus VAX systems are common.
 MFM drives (RD5x) are getting old and scarce
 RQDX series controllers are usually in the box
 SCSI and other controllers are generally had to find and not cheap

Problem:

 Hard disk storage with the following desirable characteristics:
  
	low cost
	widely available supply
	inexpensive or common interface
	Bootable by standard vax rom boots(desirable)

Solutions?

 SCSI and IDE drives are currentlly available and both can be had in 
 the .5...8Gb sizes at resonable costs(new) and wide availbility.

 Interface for both are now sub problems to be solved.

   -IDE no available qbus interface
   -SCSI existing boards expensive and most have boot or disk
    size limitations.

Which leads me to this:
	
<Just in case the usual SCSI vs. IDE flamewar is in danger of starting her

No intention as I could care less which but in the interest of a low cost 
board(and disk system) I suggested it.  

<I just want to point out that the Q-bus is far slower than either of them
<the transfer speed difference, if indeed it exists, doesn't matter.  Anyw
<one argument I can see against IDE is the 18" max cable length (or whatev
<it is, short anyway), but in a BA23 or BA123 that could be easily met (ca

It is a valid limit.  But most Q-bus boxes can accomodate several 3.5"
IDE drives in one drive bay(even ba23) as they are far smaller than RD54
and it would take 3 or more IDE(or 3.5"scsi) to equal the power and heat 
load.  Outrigger boxes are the not needed.

As an example of the above is I could put a TK50, RX33 with any 3.5"  
above it in the bays of a BA23.  There is room, power and cooling  
adaquate to support it.

<last time I had a multilayer board made we paid $70/each qty=20 for a boa
<that was a bunch smaller than a dual-height Q-bus board.  That's just for

That is expensive for a board and some shopping can be much lower.  
However, a down and dirty PIO (and possibly DMA) IDE could be done as 
two sided (two layer) dirt cheap.  Many of the older q-bus cards are 
two sided (DLV-11s, DRV-11B/P, RX11...).  In fact a simple PIO IDE
would easily be wire wrappable or could be done using the DRV-11P
logic as a foundation.  

For those not familiar the DRV11P was a quad wide wirewrap card with 
base Q-bus logic and DMA already laidin for custom designs.  The 
circuits for that are in many of the Qbus PDP-11 books from the 
early to mid 80s.  While those parts and boards are unavailable
the logic is copyable and could be put in PALs/GALs or done with 
common TTL MSI.

Again I'm not advocating a flame war.  SCSI needs micoprocessor support 
to get the protocal right, to keep the vax from really slogging and that 
is a significant cost adder that does have it's advanatages.  Also SCSI 
is a more expensive connector than IDE.  IDE does not require this and 
IDE to Q-bus is a dirt simple (READ CHEAP) PIO interface. Sure it's not 
bootable but what's needed to boot?  An RX50/33 off a RQDX1/2/3 or an 
RX01/2 all of which are common and cheap and adaquate to load a booter 
that knows this proposed card.  

Now SCSI, if you can keep the intelligence to a cheap micro like the 
8751 series would be cheaper to do than a 808x based design.  Again 
performance vs cost is the battle.  With all that has been said a $200
SCSI card is harder to achieve.

In either case the less you put on the card and the less custom logic 
the better cost wise. 

The smc37c65 chip is out of production for a while now the SMC37c655 
sort of replaces it.  Being focused at PC applications that chip also 
has serial ports, parallel printer port, and IDE interface (and some 
100 pins). 

To be fair to SCSI there may be smarter chips out there to make the 
task easier.  That would have to be researched (and their cost and 
availability too!).

<bare board, the parts add up to a few bucks (and you have to tie up a bun
<of cash in PCBs and parts to get decent qty discounts) and it takes an ho
<to stuff each board if it's done by hand.  It would be understandable to
<expect some money for the weeks/months of development too, even if it is 
<hobby project (which it need not be).

Also shipping(customs, duties) across the ocean is a factor.

Allison