My guess would be TVGA9000.
But back in the era, it was only found on 16-bit ISA cards - the 8-bit variant is modern.

Seems general across the tridents I have got that sometimes the 8 bit jumper and mode was broken out, sometimes it wasn't, sometimes it can be re-engineered if they just left stuff off.

RTG3105 from Realtek isn't a speed monster, edges out the worst Tridents, so faster than early Oak, my PT505 card is 8 bit on 16, with none of the 16bit lines connected. There are also full 16bit implementations around as well as other 8 bit ones. I think the 16bit ones have dual BIOS for odd/even.

Might need to check up about cards needing 286 instructions for their BIOS or 386 for their drivers, which can trip you up. But it has been known that the V20 or V30 has the 286 instructions needed.

Speaking of tridents, 8900D is much faster than 9000, but it’s 16 bit.

Only 8 bits I have handled are Paradise wonder if its gonna works which later became WD 90c00.

The fastest one which also still has a RAM BIOS utility? 😉

Some 8 bit speed discussions in my thread here...
Lowend 486 ISA VGA Graphics Quick Test, Mostly Tridents plus Oak, ATI, Tseng ....

Which I guess says almost everything 8 bit is at the slow end 🤣 ... PVGA1 doesn't seem real real bad though. The Tridents/CLs/C&T that are on "era" 8 bit cards aren't the later faster models, so kinda tend towards just as good/bad.

Is there an objective though? If it's trying to run Wing Commander on a 16mhz V20 then some cards might shine more for that than others.

BitWrangler wrote on 2026-02-12, 05:46:

Seems general across the tridents I have got that sometimes the 8 bit jumper and mode was broken out, sometimes it wasn't, sometimes it can be re-engineered if they just left stuff off.

RTG3105 from Realtek isn't a speed monster, edges out the worst Tridents, so faster than early Oak, my PT505 card is 8 bit on 16, with none of the 16bit lines connected. There are also full 16bit implementations around as well as other 8 bit ones. I think the 16bit ones have dual BIOS for odd/even.

Might need to check up about cards needing 286 instructions for their BIOS or 386 for their drivers, which can trip you up. But it has been known that the V20 or V30 has the 286 instructions needed.

realtek3105i is the slowest 512kb card that i know of, save for the pvga1 waiting to be tested, which is probably on par. note that the 3105ieh is quite a bit faster, but still no match for the chips450.
and i don't believe that there are any 3105(series) chips with 16 bit isa data pins, can you post a picture of full 16bit card with 8 high data pins connected to chip?

Fun fact - later models 16-bit ISA VGA cards are actually slower than early models when inserted in XT 8-bit slots.
The fastest graphics chip for this class systems seems to be Western Digital WD90C00.
All the listed above cards in the thread are verified slower.
Same goes for the classic champions ET4000AX and TVGA8900L/CL.
CL GD-5434 does not light up on anything below 386 (maybe with a HW mod it will, bit in default config it is not even a contender).

What's the purpose of this inquiry? If it's theoretical/for discussion I get it of course, but if you're looking for the fastest VGA to put on your XT I don't believe that in practice you'll benefit much from it.

pshipkov wrote on Yesterday, 07:51:

Fun fact - later models 16-bit ISA VGA cards are actually slower than early models when inserted in XT 8-bit slots. The fastest […]
Show full quote

Fun fact - later models 16-bit ISA VGA cards are actually slower than early models when inserted in XT 8-bit slots.
The fastest graphics chip for this class systems seems to be Western Digital WD90C00.
All the listed above cards in the thread are verified slower.
Same goes for the classic champions ET4000AX and TVGA8900L/CL.
CL GD-5434 does not light up on anything below 386 (maybe with a HW mod it will, bit in default config it is not even a contender).

oh really, that sounds dubious but maybe faster cards were simply designed with AT in mind and therefore doesn't perform well on an XT.

pshipkov wrote on Yesterday, 07:51:

The fastest graphics chip for this class systems seems to be Western Digital WD90C00.
All the listed above cards in the thread are verified slower.
Same goes for the classic champions ET4000AX and TVGA8900L/CL.

I have a Turbo XT board that runs the ISA bus at 0 XT waitstates at 4.77MHz and 1 XT waitstate at 10 MHz. Note that by "0 XT waitstate" I mean the timing generated by the 8088 processor, which requires four bus clocks, so this is comparable to 2 AT waitstates, as the bus cycles generated by the 80286 processor only take 2 clocks, so for effective throughput, the two extra clocks required by the 8088 bus protocol are equivalent to two extra waitstates in the 80286 bus protocol.

With a V20 processor, which is able to saturate the bus on REP STOSW, I observe full theoretical throughput with both an ATI Mach32 as well as the ET4000AX cards that happen to work in 8-bit slots. This is 1.193MB/s at 4.77MHz and 2.0MB/s at 10MHz. These values have been extrapolated from testing at different RAM refresh intervals for a theoretical throughput with RAM refresh disabled. So I can not confirm the claim that there are cards that are faster in an XT than my ET4000AX card.

mkarcher wrote on Yesterday, 18:19:

I have a Turbo XT board that runs the ISA bus at 0 XT waitstates at 4.77MHz and 1 XT waitstate at 10 MHz. Note that by "0 XT waitstate" I mean the timing generated by the 8088 processor, which requires four bus clocks, so this is comparable to 2 AT waitstates, as the bus cycles generated by the 80286 processor only take 2 clocks, so for effective throughput, the two extra clocks required by the 8088 bus protocol are equivalent to two extra waitstates in the 80286 bus protocol.

With a V20 processor, which is able to saturate the bus on REP STOSW, I observe full theoretical throughput with both an ATI Mach32 as well as the ET4000AX cards that happen to work in 8-bit slots. This is 1.193MB/s at 4.77MHz and 2.0MB/s at 10MHz. These values have been extrapolated from testing at different RAM refresh intervals for a theoretical throughput with RAM refresh disabled. So I can not confirm the claim that there are cards that are faster in an XT than my ET4000AX card.

Excellent, thanks for the info. But does the ati mach32/64 have isa 0wait mode? I can't find any on my mach64 dram.
In my tests on a 486 with 8.3mhz isa bus, cards with 0wait support all top out at ~4mb, while cards without can achieve ~3.2mb, which translates into 4 and 5 clocks per transfer.
slowest true 16bit isa card that i know of is the et3000, at ~1.3mb, thats ~12 clocks per transfer, and single byte transfer is even slower than oak037 as is in doom, only faster than ibm vga.
as for 8bit cards(including faked 16bit cards with only 8 data pins), i only have chips450(7clocks), realtek3105ieh(8clocks), realtek3105i(9clocks), oak037(11clocks) and ibm vga(15 clocks), with a pvga1 left to test.

@mkarcher
With such a slow system you are more right than wrong - differences will be minimal.
I run NEC V30 (8086) at 17-18MHz, decoupled ISA bus at 14.3MHz.
Differences between 30 or so ISA video cards are more visible.
Had a post with details somewhere about that ...

pshipkov wrote on Today, 02:15:

@mkarcher With such a slow system you are more right than wrong - differences will be minimal. I run NEC V30 (8086) at 17-18MHz, […]
Show full quote

@mkarcher
With such a slow system you are more right than wrong - differences will be minimal.
I run NEC V30 (8086) at 17-18MHz, decoupled ISA bus at 14.3MHz.
Differences between 30 or so ISA video cards are more visible.
Had a post with details somewhere about that ...

guess thats quite overspec and not within what i count as an xt. or to say, what i meant was a plain 8088 without extensions, mentioning xt just for short.
while controversial, i would count amd5x86 but not pod and cyrix5x86 as a 486 platform.

16-bit ISA video cards are a next gen technology compared to XT machines.
It is the same as mismatching latest gaming GPU with an old cpu - you wont get much out of the discreet graphics card in cpu bound games and benchmarks.
So, if the premise is “vanilla XT” then yes - it kind of does not matter what the vga card is … as long as it is not Realtek.

IMO the upper limit for "turbo XT" is still 8-bit external data bus, I don't see how the V30 could be considered an XT by any stretch of the imagination

XT is a PC‑class system with an 8088/8086 CPU, 20-bit physical address bus (up to 1Mb of directly addressable system memory), no protected mode, 8‑bit expansion slots.
The external data bus is not a differentiator in the same way how present day lower tier 5000 series nvidia gpu has a narrower memory interface but is still a 5000 series hardware.

pshipkov wrote on Today, 17:14:

XT is a PC‑class system with an 8088/8086 CPU, 20-bit physical address bus (up to 1Mb of directly addressable system memory), no protected mode, 8‑bit expansion slots.

Well, yes and no. It depends on someone's definition.
In general, the XT is being defined by the motherboard design of IBM PC 5160 and its architecture.

The AT, for example, was an XT extension with a standard Real-Time Clock (RTC), a real keyboard controller (8042 based mircrocontroller),
16450 UART, the AT BIOS, AT bus (80286 front-side bus), secondary DMA/IRQ controller.

So if someone shoehorns an 8086 or 80186 in a PC/AT motherboard design it's not suddenly becoming an XT.
Key elements of AT architecture such as standard Real-Time Clock, AT BIOS and the cascaded DMA/IRQ controllers are still there.
Even 16-Bit wide I/O is possible (=ISA cards can work), albeit limited to 20 Bit address range.

Let's call it an E.T. architecture! 😁
(Enhanced Architecture)

Edited. Multiple edits.

Edit: @pshipkov I didn't meant to say your statement was wrong.
I rather meant that there's more to it.
The Japanese PC-9801 for example is an 8086 PC running DOS, too, but it's not an XT.
The memory layout, the i/o ports and software/hardware interrupts are different, among other things.
And back in the 80s, the west also had "MS-DOS compatibles" that weren't XT architecture.

Edit:

16-bit ISA video cards are a next gen technology compared to XT machines.

Umm.. Depends, I think. Back in 1987-1990, both the 16-Bit and 8-Bit VGA cards used same chip.
- The Paradise PVGA1A was used on an 8-Bit budget card that was limited to 256KB of video RAM, for example.

Users who wanted or needed 512KB or 1MB of video RAM had to get the 16-Bit models.
No matter if they had an PC/XT or AT. The higher end models worked in either slot.

https://dosdays.co.uk/topics/Manufacturers/pa … rofessional.php

IMO the upper limit for "turbo XT" is still 8-bit external data bus, I don't see how the V30 could be considered an XT by any stretch of the imagination

The Amstrad PC 1512 and 1640 used 8086 CPU and were popular IBM compatible PCs back in ca. 1986.
The V30 CPU also was often used as an upgrade. Not sure if they were considered XTs or not, though.

E.T. class you say?
Approved.

I listed the 4 defining architecture characteristics.
The presence or absence of various other controllers and circuitries introduced is a lesser factor, but they do blur the picture - your examples with European and Japanese designs are a good illustration of that.

16-bit ISA video cards are clearly a next-generation product aimed at 286-class and later systems, not at XTs. We don't even need to look at details as the 8-bit / 16-bit ISA interface difference is visible from Mars.
They include backward compatibility because XTs remained common long after the 286, 386, 486, and even the first Pentiums appeared, but nobody was actively optimizing for XTs by then.
When designing a new hardware or software product, you target current and upcoming platforms. Product management may ask for support for the last few legacy platforms, but the associated KPIs are much looser - usually in the form of maintained stability and no major performance regressions (which equates to no optimization effort).
So, my findings that older VGA chips/cards seem to do better with XTs may not be unfounded, or at least that's the theory.