Under pure DOS + pentium2+ systems you need a special utility to speed up graphics performance, try one of the 3 linked here: http://www.mdgx.com/umb.htm#FAS
You don't need any kind of VESA driver for the riva128 cards, they already have a VBE3.0 bios 😎

By DOS, do you mean DOS 7.0/7.1 in real mode, or a DOS command prompt (window) from within Windows?
If real mode DOS, then you need to check what you are loading at startup.
You could try Fastvid - refer this topic: VESA Fix Utility Listing (for old video cards)

Real mode, and thank you kindly.

So basically (according to http://download.intel.com/design/PentiumII/ap … ts/24442201.pdf), the Pentium architecture did some equivalent of write combining at the chipset level achieving 70 MB/s PCI VGA/SVGA graphics throughputs. Later architectures starting with Pentium Pro are limited (8-20 MB/s performance on a 200 MHz PPro, depending on other chipset features) unless graphics write combining is enabled in the CPU's MTRR registers (40-100 MB/s on the same system).
FASTVID or one of a couple alternative programs (MTRRLFBE v1.3 is one that's compatible with EMM386 and equivalents) is needed to enable WC in pure DOS; it should already be enabled by default under Win9x and even after "restarting" to DOS from Windows.