Re: TWGS DMA and RamFast SCSI--HELP!!

[Liam Busey <liam1@ix.netcom.com>]

Sagochangi wrote:
> 
> I read a while ago (from Supertimer) that the TWGS is fully DMA > compatible with the RAMFast SCSI controller.  And that certainly isn't > the first time I've heard that. But my experience has been different. > I bought a TWGS a while ago, anxious to use all the new speed. But the > card absolutely refuses to boot with my RamFast in the system, even > with the RamFast set to TWGS: YES, and DMA off.
> 
> Nathan Mates' old accelerator FAQ lists the -2B GAL as being a 
> necessary DMA fix, and the RamFast manual itself (p.40) says of the 
> -2B GAL, "The RamFAST/SCSI will not function in your computer until 
> you get this replacement part".  And the TWGS works fine without the 
> SCSI card in the system, so I can only assume that I do need the chip.

I wouldn't put much seock in Nathan's  Accelerator FAQ. It's way out of
date. As for the 2B GAL requirement, I believe Tony Diaz is correct in
his assessment that it's unneccessary. I've seen a a couple of posts
from people Ramfast Transwarp difficulties even with the 2B GAL
installed.

A stupid question. Does your Ramfast function properly without the TWGS?

 
> Tony Diaz shows a completely compatible RamFast card on his site, rev > D (same as mine), although chip U9 on his card is v3.00, whereas mine > is 3.01F.  Could this make a difference?

I wouldn't think so. The IC located at U9 appears to be the Ramfast's
ROM. I don't see why Sequential would release a less compatible version
of it's firmware as an update. Other than that, your cards should be
identical. 

> Here, also, is the information I've gathered on my TWGS: version 8H, 
> rev. 1.4x. Performs at 6.3 mHz in Transwarp mode.  Card is installed 
> in slot 3 on a ROM 03.

Your TWGS is appears to be significantly different from his though.
Tony's has the improved 65816, a different ROM, an expanded cache, and a
faster oscillator.  

> Can anyone tell me if there is a work-around for this problem?  If 
> not, please, *please* (he wrote with his own blood), can some kind 
> soul tell me where I can get the -2B chip?  I can't give up my hard 
> drives, but I can't keep going at 2.6 mHz, either. Replies by email 
> are appreciated.

The only place your likely to find a 2B GAL these days is on another
TWGS. So unless you get lucky your stuck.

<hypothesis>
If I recall correctly, Tony Diaz's TWGS Mod site said that the GAL
upgrades on the TWGS accelerator where made to compensate for the bugs
in the design of the original 65816 when running at higher speeds. I
suspect that the 2B GAL (which supposedly allows compatibility with the
RAMFAST controller) is not extra logic to interface with the RAMFAST but
rather logic to clean up flakiness in original 65816 DMA. Perhaps the
redesigned 65816 no longer needs the GALs? That could explain why Tony's
TWGS was compatible and yours currently isn't.
</hypothesis> 

Liam Busey