here are the diffs from my small mods to support the 4000/600 cache,
against -current of about 6 days ago (1.5S) :

in /sys/arch/vax/vax, 

# diff ka680.c OLDka680.c
34d33
< /* minor modifications for KA690 cache support by isildur@vaxpower.org */
120d118
<               case VAX_STYP_690: cpuname = "KA690"; break;
148,152c146
<       switch((vax_siedata & 0xff00) >> 8) {
<               case VAX_STYP_675: 
<               case VAX_STYP_680: slut=0x01420000; break;
<               case VAX_STYP_690: slut=0x01440000; break;
<       }
---
>       slut  = 0x01420000;
162,166c156
<       switch((vax_siedata & 0xff00) >> 8) {
<               case VAX_STYP_675: 
<               case VAX_STYP_680: slut=0x01020000; break;
<               case VAX_STYP_690: slut=0x01040000; break;
<       }
---
>       slut  = 0x01020000;
188c178
<       if((((vax_siedata & 0xff00) >> 8) == 
VAX_STYP_680)||(((vax_siedata & 0xff00) >> 8) == VAX_STYP_690)){ 
---
>       if(((vax_siedata & 0xff00) >> 8) == VAX_STYP_680) {


and in /sys/arch/vax/include:
# diff OLDsid.h sid.h
161a162
> #define       VAX_STYP_690    0x07            /* VAX 4000 model 600 */



happy hacking,
isildur