First post, by majestyk
The DFI K6XV3+/66 is a great socket 7 mainboard and I used it in one of my office PCs for years. For no obvious reasons most of the sold mainboards of this model had 512K onboard cache, a few had 2MB (unlike the baby-ATX version that came with 1MB or 2MB more often).
I decided to upgrade one of my 512K boards with a second 512K chip. After soldering the additional chip I intended to have a look at some picture on the web to find out about the jumpering (=positioning of the 0 Ohm resistors) for this configuration, because I only own 512K and 2MB versions.
I was surprised to find next to nothing - loads of 512K boards and a few blurry ones of the 2MB version.
So I had to find out myself. Here are the results:
Resistors R111, R112 and R113 are just for adjusting the cache size shown in the BIOS summary screen (and maybe tell the MCH what cache size to expect).
R111 -> 1024K
R112 -> 2048K
R113 -> 512K
But that´s not all. For 512K the address line A14 of the 32Kx8 TAG chip is grounded by R134 (the one at the bottom of the red circle).
For a cache size of 1Mb this resistor has to be moved to position R133 (the one above R134) to connect it to the MCH.
This is all that´s to be done for 1MB L2 cache.
If you want to upgrade to 2MB, both 64Kx64 SRAM chips must removed and replaced by 128K64 chips and R113 has to be moved to position R112.
In addition R127/R128 and R129/R130 have to be adjusted for the different pinout.
I did not do this here for a reason: For 2MB cache you need a 64Kx8 TAG RAM (32-pin) with 8nS "speed" that offers the additional address lines. The layout of the K6XV3+ is prepared for this but these chips are very very hard to find today.
There are still 128Kx8 chips made today but I never found 8nS ones. If someone has a source for such chips please let me know.
And here´s a picture of the "finished product" (the sticker still says 512K):