440ZX is similar to 440BX, notably it lacks parity/ECC and SMP support. it's not 100% clear whether it carries over the improvements that 440BX introduced over 440LX (better buffering etc.), but it's said to be based on the same core design, so it might. there is an inconsistency regarding memory support, though; the 440ZX spec sheet claims 256 MB max, while the P2-99 board manual says 512 MB max.

According to Intels own datasheets the 440ZX supports:
"Integrated DRAM controller — 8 to 256Mbytes
— Supports 2 double-sided DIMMs (4 rows memory)"
the 440BX supports:
"Integrated DRAM controller— 8 to 512 Mbytes or 1GB (with registered DIMMs)
— Supports up to 4 double-sided DIMMs (8 rows memory)"

Besides the motherboard chipset, there are two more differences between these motherboards.

One is the PLL clock generator chip they use. ASUS P2B rev 1.02 usually has the ICS9148BF-26 that is fully supported by RayeR's SMB utility for changing the FSB speed on the fly in DOS, with the option to use 50 MHz FSB. ASUS P2-99 rev 1.12 has the ICS9248DF-39 instead, where the minimum FSB speed that can be set is 66 MHz and unofficially works with the aforementioned utility.

The other one is that the P2-99 lacks hardware monitoring support.

Thank you for your replies. So it looks like P2B is the better of the two? How about coppermine support and 133 mhz FSB? Over here https://theretroweb.com/motherboards/s/asus-p2-99on the main page, it is mentioned that 440ZX supports upto 150Mhz FSB (really?). However the manual only states 66 and 100Mhz. Moreover, the manual also doesn't specify any official coppermine support but have read some info that ZX does work with it primarily using slotket.

The manual only states the FSB speeds that both Intel chipsets officially support. Overclocking them at least to 133 MHz FSB has the caveat of the AGP bus running at 89 MHz and requiring quality PC133 SDRAM sticks, anything higher is impractical.

About Coppermine support, both Slot 1 and Socket 370 (with the Slotket adapter) CPUs runs on the P2-99 rev 1.12 without much hassle.

440ZX supports 512 MB RAM (2x 256 MB w 16 chips), same FSB's as BX, and lacks multiprocessor support and ECC.

Regarding 440ZX + ECC, I have an A-Trend ATC-6310M and interestingly it worked just fine with ECC REG memory. I'm not sure if the memory just worked and those features were disabled, but CPU-Z reported the features and the board worked just fine with it installed.

https://theretroweb.com/motherboards/s/a-trend-atc-6310m

Gmlb256 wrote on 2024-12-24, 21:25:

Besides the motherboard chipset, there are two more differences between these motherboards.

One is the PLL clock generator chip they use. ASUS P2B rev 1.02 usually has the ICS9148BF-26 that is fully supported by RayeR's SMB utility for changing the FSB speed on the fly in DOS, with the option to use 50 MHz FSB. ASUS P2-99 rev 1.12 has the ICS9248DF-39 instead, where the minimum FSB speed that can be set is 66 MHz and unofficially works with the aforementioned utility.

The other one is that the P2-99 lacks hardware monitoring support.

I can confirm being able to adjust the FSB down to 50Mhz FSB with that utility. There's a quirk however with this board that I don't have on a different brand with the same clockgen: After clocking down to 50Mhz FSB, you can't go back up to a higher FSB.

Cosmic wrote on 2024-12-25, 20:34:

Regarding 440ZX + ECC, I have an A-Trend ATC-6310M and interestingly it worked just fine with ECC REG memory. I'm not sure if the memory just worked and those features were disabled, but CPU-Z reported the features and the board worked just fine with it installed.

https://theretroweb.com/motherboards/s/a-trend-atc-6310m

not too surprised that it would run, but the 82443ZX spec sheet is quite clear on it not supporting the required signals. also, registered memory probably runs slower than unregistered would due to the extra buffering.

if that's not enough and you want to see for yourself, the old CTRAMTST (CTRAM51.EXE) tool is supposed to be able to test ECC.

mockingbird wrote on 2024-12-25, 21:02:

I can confirm being able to adjust the FSB down to 50Mhz FSB with that utility. There's a quirk however with this board that I don't have on a different brand with the same clockgen: After clocking down to 50Mhz FSB, you can't go back up to a higher FSB.

This was done for P2-99 or P2B? If I understand, the FSB clocking up can't be done during the current session but could be in the next restart.

stealthjoe wrote on 2024-12-26, 04:08:

This was done for P2-99 or P2B? If I understand, the FSB clocking up can't be done during the current session but could be in the next restart.

I tested with the P2B and P2B-S. The P2B-S has the ICS9150-08 which also does 50Mhz FSB and it works with RayeR's utility but has the same issue.

Do you already own these or are they 2 options for purchase?
If its to buy I'd go on cost. Yeh the ZX is the "budget" chipset but Intel removed features that aren't going to hurt a retro build.

chinny22 wrote on 2024-12-27, 00:05:

Do you already own these or are they 2 options for purchase?
If its to buy I'd go on cost. Yeh the ZX is the "budget" chipset but Intel removed features that aren't going to hurt a retro build.

These are the options to buy. Strangely, the ZX is the slightly more expensive one ($97) as compared to BX (few dollars less). Wondering if it due to the coppermine support on ZX. The listing does include a VGA card, processor and RAM in both the cases.Processor : 600Mhz Coppermine (ZX) vs 333 Mhz (BX), RAM: 256MB (ZX) vs 128MB (BX), Riva TNT2(ZX) vs ATI RageIIC (BX) . Any thoughts on the better option?

it's all a bunch of old PC hardware, so "better" is a strange question. it simply depends on what you are trying to do.

the TNT2 is arguably better matched to its processor, especially if it's not the M64, but someone could want the rage card for trying to play ATICIF games.

auron wrote on 2024-12-27, 16:04:

it's all a bunch of old PC hardware, so "better" is a strange question. it simply depends on what you are trying to do.

the TNT2 is arguably better matched to its processor, especially if it's not the M64, but someone could want the rage card for trying to play ATICIF games.

I was looking for primarily DOS gaming with some late 90s Win gaming. First my focus was on the P2-99, but reading few of the above posts on the FSB flexibility in P2B, a little confused now 😀

If DOS gaming is a priority, then go for the TNT2 card which has better compatibility than the ATi. With UniVBE after some patching, you get 15bpp support and some low resolution VESA video modes.

TNT2 is too old and will bottleneck even a Pentium MMX. There's no reason not to use a Geforce 4 MX... The SciTech patch works with it as well.

How about Throttle compatibility with Asus boards and in general DOS slowdown options with BX and ZX? Read here that Throttle doesn't work well with Asus bios and there seems to be another version(Asus P2B - thpiix4e.exe - throttle.exe for Intel PIIX4E "Throttle" slowdown utility).

mockingbird wrote on 2025-01-01, 02:39:

TNT2 is too old and will bottleneck even a Pentium MMX. There's no reason not to use a Geforce 4 MX... The SciTech patch works with it as well.

Yep, the patch mostly worked well on my GeForce2 and bet the OP would likely use a better video card afterwards.

The only reason I didn't mention GeForce cards was due to having issues with some early Windows games that aren't present on the TNT2. Some good examples are the HUD in Incoming and the stars in Thief.

stealthjoe wrote on 2025-01-01, 03:34:

How about Throttle compatibility with Asus boards and in general DOS slowdown options with BX and ZX? Read here that Throttle doesn't work well with Asus bios and there seems to be another version(Asus P2B - thpiix4e.exe - throttle.exe for Intel PIIX4E "Throttle" slowdown utility).

I can confirm that the official version of Throttle does nothing on ASUS motherboards, only the modified one (note that Throttle will disable the L1 cache by default, use the -C command line switch to avoid that) in the last post from that link or CPUSPD has any effect.

As for general DOS slowdown options, there is an obscure one that can be achieved with CM utility to set the CPU cache control to write-through. The disadvantage is that it only works in real mode or if JEMM is used in situations where EMS is needed.