Tseng Labs ET4000

The Tseng Labs "ET4000" was a line of SVGA graphics controller chips during the early 1990s, commonly found in many 386/486 and compatible systems, with some models, notably the "ET4000/W32" and later chips, offering graphics acceleration. Offering above average host interface throughput coupled with a moderate price, Tseng Labs' "ET4000" chipset family were well regarded for their performance, and were integrated into many companies' lineups, notably with Hercules' "Dynamite" series, the Diamond "Stealth 32" and several "Speedstar" cards, and on many generic boards.
Models.
ET4000AX.
The "ET4000AX" was a major advancement over Tseng Labs' earlier "ET3000" SVGA chipset, featuring a new 16-bit host interface controller with deep FIFO buffering and caching capabilities, and an enhanced, variable-width memory interface with support for up to 1MB of memory with a ~16-bit VRAM or ~32-bit DRAM memory data bus width. The FIFO buffers and cache functions had the effect of greatly improving host interface throughput, and therefore offering substantially improved redraw performance compared to the "ET3000" and most of its contemporaries. The interface controller also offered support for IBM's MCA bus, in addition to an 8 or 16-bit ISA bus. The "ET4000AX" could also support the emerging VESA Local Bus standard with some additional external logic, albeit with a 16-bit host bus width.
Neither the "ET4000AX" or its succeeding family members offered an integrated RAMDAC, which hampered the line's cost/performance competitiveness later on.
ET4000/W32.
Hardware acceleration via dedicated BitBLT hardware and a hardware cursor sprite was introduced in the "ET4000/W32". The "W32" offered improved local bus support along with further increased host interface performance, but by the time PCI Windows accelerators became commonplace, high host throughput was no longer a distinguishing feature. Nevertheless, as a mid-priced Windows accelerator, the "W32" benchmarked favorably against competing mid-range S3 and ATI chips. Configured with 32-bit asynchronous EDO/FPM (70 ns) DRAM, the "W32" could sustain a transfer speed of 
ET4000/W32i.
The /W32i revision featured an interleaved 32-bit memory bus (with 2MB+ of memory) to improve memory throughput. It supports a maximum of 4 MB of video memory, though most boards featuring the chip typically offer a maximum expansion of 2MB or less.
ET4000/W32p.
The "W32p" model offered support for the PCI bus, although earlier revisions of this chip (prior to Revision D) had some design problems that caused sub-optimal or problematic operation when used in PCI implementations, although VLB implementations were unaffected.