Hello,

     [ ... johnam@kemper.org asked me personally about TC framebuffer ... ]
 
> I've a friend sending me a PMAGC-BA also.  Where does this stand in the   
> DECstation hardware support world?  I've looked through all of my old DEC   
> catalogs (90, 92, 93) and the PMAGC-BA and PMAGD-AA are not referenced   
> anywhere.

PMAGC (PV == PixelVision) and PMAGD (HX+) were originally developed
for DEC3000 (TURBOchannel Alpha machines), not for MIPS based
DECstation. (If Digital kept MIPS way we had the plenty supply of
R4400/R4000 DECstations nicknamed 4MAX+ and 4MAXINE).

> I've got a PMAGB-B, is there really any advantage of the PMAGD or PMAGC   
> over the PMAGB-B?

Yes, it should have.  But not terribly nicer than the original HX.
The design and approach is identical w/ some 'improvement' (I don't
like it personally because it hurted the virtue of HX design)

> You sound fairly knowledgeable, maybe you can answer this, the -AB -B   
> suffixes are they revisions of the parent PMAG* prefix?  I.e. are all   
> PMAGB-** all the same basic card with subtle differences?

It's very confusing.  Their naming strategy was;

	PMAG_-__   TURBOchannel framebuffers

The first _ is blank or letter B.  PMAG-__ is the first generation of
TURBOchannel framebuffer; PMAG-A ("8bpp monochrome" MX), PMAG-B (256
psuedocolour, CX), PMAG-C/PMAG-D/PMAG-E/PMAG-F (PX and PXG family),
PMAG-RO/JA (256 psuedo and 24bpp true with RasterOps picture in
picture video compositor and frame grabbing circuit, TX). 

PMAGB-B (HX) is equipped with SFB which completely redefined the bottom
line of 2D graphic standard.

There were variations of PMAGB-[DEFJ]_ for higher screen refresh
frequency (72Hz and possibly the original). 

PMAGC was designed to replace PX/PXG combined with SFB philosophy.
PMAGD had a new feature of multiple screen size/frequency and there
are two variations for 256 psuedo colour and 24bpp true colour.

The last letter is the hardware revision or variation, and should not
make matters for software's points of view. 

Tohru Nishimura
Nara Institute of Science and Technology