Re: Transwarp GAL chips

[pubpc1@library.ucla.edu]

Rubywand wrote:
>      Someone with TWGS experience or knowledge of alternative cache
> upgrade methods is going to have to come to the rescue here. Just
> guessing: It is conceivable that, however correct your hardware mods,
> the 65C816 will not send the required address signals to your new 32k
> memory IC's without the v1.7 ROM.

///SHH Systeme can provide the needed ROM (note: this ROM is
only needed for cache upgrades....the speed upgrade would
work with 1.5 ROMs)

> 
>      By the way, John Link mentions that a speed upgrade can be done to
> boards having the v1.5 ROM. The 1991 series of articles ends with a
> fairly involved upgrade to 10MHz. This, was, evidently, before the
> better 65C816's arrived.

Yep.  Unfortunately, the FAQ seems to be based on this dated
info.

> 
>      In 1992, John Link welcomes WDC's new, improved 65C816's with
> another speed-up article involving much less bother. He says that he
> obtained reliable operation at 12.5MHz without increasing Voltage and,
> as noted by Scott G, without swapping out GALs.

Yes.  The GALs provided traps that slowed the board when the
older 65C816's were executing certain instructions.  The new
and improved 65C816 (ie. the "14 MHz" units sold today) do not
have problems with these instructions at high speeds, so the
GALs don't have to be swapped.

> 
>      The catch here is that he had earlier installed the AE 32k cache
> upgrade which happened to include 35ns RAM. The original 8k RAM was
> rated at 45ns. Also, there seems to be no mention of ROM speed
> differences, if any.
> 
> Rubywand


Actually, John Link didn't get a chance to test the original
45ns chips, but the board I upgraded had the original 8K 45ns
SRAMs.  The upgrade still worked.

What I don't understand is why the FAQ mentions wildly fast
SRAM numbers for accelerator upgrades.  My Zip, for example,
runs fine with 15ns in TAG and 70ns in cache and it is very
fast.  I suspect that the fast SRAMs were needed because,
as with the GALs, the older "engineering" 65C816 had lower
tolerances than the modern "14MHz" 65C816S chips.

-Scott G.