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From: knudsen@ihlpl.ATT.COM (Knudsen)
Newsgroups: comp.sys.m6809,comp.os.os9
Subject: Chris Burke (& Burke) on the BLOB
Keywords: BLOB, Coco, OS9, hardware, HD
Message-ID: <7423@ihlpl.ATT.COM>
Date: 28 Oct 88 19:02:34 GMT
Article-I.D.: ihlpl.7423
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 40

Last nite at our monthly meeting of the Chicago OS9 Users' Group,
the guest speaker was none other than Chris Burke (half of B&B)
himself.  I asked him about the BLOB problem and the E-clock gating.
He had certainly heard of it!  His response was as follows:

(1) The Cocos do not gate the peripheral device select SCS-
(the FF40 range strobe) with E-clock themselves.
[This is probably good, since a device should know ahead of time
that it is selected.  By "time" I mean the E clock pulse.]

(2) So each peripheral should gate its own internal enables with
E clock.  Some don't, including my old DISTO Ramdisk and early
models of the B&B HD adapter.  New B&Bs do, and he showed us one
with the extra IC on it.

(3) He said I could hack the fix into my old B&B as follows:
Stick another 74LS00 quad-NAND chip on it somewhere.
Feed SCS- into both inputs of one gate (pins 1 & 2) to
get de-inverted SCS+ out of pin 3.  Feed this to one input
of a second gate (pin 4).  The other input (pin 5) gets E-clock
off the Coco bus.  The output on pin 6 is the gated SCSE-.
Cut the original SCS- feed from the Coco bus into the PC bus,
and feed the new SCSE- into the PC bus.
Oh yes, feed Ground to pin 8 and +5 to pin 16, helps a lot ;-).

I haven't had any BLOB problems, but then I avoid making new boots
like the plague, tho there are several reasons for me to make
another one.  I may or may not go thru with this mod, depending on
how my new boots work out.

(4) This isn't BLOB-related, but Chris will soon have a universal
Coco-->PC-bus adapter that will handle up to four of ANY PC card.
Including an MPU-401 clone board for us MIDI musicians.
This will be aimed at hackers who repackage their Coco system
into PC cases.  [Thanks to the Burkes, we can salvage just about
everything of a PC except the motherboard :-) ].
-- 
Mike Knudsen  Bell Labs(AT&T)   att!ihlpl!knudsen
"Lawyers are like nuclear bombs and PClones.  Nobody likes them,
but the other guy's got one, so I better get one too."