10 Nov
2006
10 Nov
'06
10:17 a.m.
Julian Wolfe wrote:
There's a utility called 'fastv20' that
speeds up NEC V20 chips, and fixes a
compatibility problem with them through software. I don't exactly remember
what it does to make it faster, since I don't have the docs in front of me
right now. It does do a pretty good job though!
Found it. I was somewhat disappointed:
mov al, 74h
out 43h, al ; Timer 8253-5 (AT: 8254.2).
mov al, 8Fh
out 41h, al ; Timer 8253-5 (AT: 8254.2).
mov al, 2
out 41h, al ; Timer 8253-5 (AT: 8254.2).
int 20h ; DOS - PROGRAM TERMINATION
This is the standard "reduce DRAM refresh rate so CPU has more leftover
cycles" trick. It has nothing to do with V20's at all, it works on any
XT. I was rather hoping it was something V20/V30-specific.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
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