First post, by majestyk
- Rank
- Oldbie
While searching for a useful application for a Am5x86 AWD that refuses any overclocking attempt but works perfectly at 4 x 33MHz, I came across my Asus PCI/I-486SP3G Rev. 1.8 that is limited to 33 MHz due to it´s Saturn II chipset.
But before proceeding I did some tests with a regular DX4 and the memory performance was dissapointing. The reason was a missing Dirty-TAG chip. After adding a 64K x 1 SRAM chip, the "ctcm" output was finally: "Dirty TAG L2 -> o.k." Memory performance showed the charakteristic increase.
I then replaced the DX4 with the Am5x86, jumpered everything accordingly, L1 Write Back gets enabled, but Dirty-TAG gets turned off, so the L1 performance gain is (partly) eaten by the decreasing L2 performance.
The reason here ist that the Dirty-TAG´s chip enable# input is connected to pin 3 of JP36. This jumper is is for different purposes - depending on the CPU type, but for L1 WB it needs to be set to 1-2 (instead of 2-3) and "chip enable#" is no longer pulled down which means the chip turns inactive. Lifting pin 12 of the TAG chip and connecting it to ground fixes this issue.
There´s a jumper for "CACHE" (none for "INV") and one for "HITM" that connects the CPU´s HITM output to some pin of the chipset, but closing that jumper turns off Dirty-TAG again.
How can I tell if this solution is stable and if it´s the optimum?