8-bit IDE hard drives, controllers

[Herb Johnson - null account]

-- Jim Leonard posted:

 >Search these archives for a similar post; there are indeed 8-bit ISA
 >IDE interface cards that work with IDE drives up to 540MB.  I have
 >one of them but haven't dragged out my 5150 to try it out yet
 >(sidetracked on another project).

Just want to note that my posted remark was on very old ISA IDE 
controller cards that used an 8-bit DATA PATH to the *IDE drive* - an 
alternative to the IDE DRIVE standard of 16 data bits. Don't confuse 
this with "8-bit ISA" and "16-bit ISA" cards which refer to the *ISA bus*.

What are often called "8-bit ISA cards", have a single edge connector to 
the IBM PC ISA bus. With the IBM AT, IBM introduced the "16-bit ISA bus" 
with TWO bus edge connectors to provide a 16-bit data (and additional 
signals) AT THE BUS. These later cards were also called "AT-style" ISA 
cards, as I recall.

So the above statement by Mr. Leonard is a little ambiguous. He probably 
is referring to the ISA bus, not the IDE connector, as being "8-bit". My 
impression is that few IDE drives were 8-bit. But as many people on this 
list run and restore old systems, they may run across (or require) 8-bit 
IDE drives and compatible controllers.

One reason I mentioned these 8-bit IDE drives, was my reaction to a post 
about the availability of GIDE interface cards - there is an historic 
connection. I was the first person to distribute the GIDE in the United 
States. I got my first card after the Trenton Computerfest at a "Z-fest" 
gathering one evening during the show, and we attempted to demonstrate 
the card there. But the drive I obtained at the 'fest to test the card 
was only partially operational. That drive turned out to be an "8-bit" 
IDE drive as I've described. Most of the function of the GIDE interface 
is to transform 16-bit data to and from an IDE drive into sequential 
pairs of 8-bit data for the Z80 processor. (The GIDE plugs directly into 
the Z80 socket, as a daughtercard.)

Herb Johnson
-- 

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