Some dumbass asked a similar question a while back 386/486 boards? Motherboards with a socket for both a 386 and 486... So IDK if any of the replies there touch on relevant aspects.

BitWrangler wrote on 2024-09-22, 01:53:

Some dumbass asked a similar question a while back 386/486 boards? Motherboards with a socket for both a 386 and 486... So IDK if any of the replies there touch on relevant aspects.

My board isn't really 386/486. I can install only 386 because its lacks of socket and components for 486 but chipset is 486

I'm of the opinion that best 386 chipset is a 486 chipset, you get proper support for the Cyrix CPUs with internal cache. Performance of 486 chipsets is usually better too and you get more out the 386 than otherwise.

In that linked thread ppl were speaking of the advantages of a 386 on a "486" board which would also apply to chipset. Though depending on chipset, some were more like designed for 386, pressed into service for 486, and being by the time 486 got cheap, cheap themselves, became widespread so more associated with 486 than 386.

Thanks for replies. I will upgrade this board with cyrix when i get it.

What chipset is it?

MikeSG wrote on 2024-09-22, 08:05:

What chipset is it?

ALi M1429G

As the 386 and the 486 front-side busses are quite similar, having a chipset support both isn't that difficult. Obviously, the 386 does not do burst cycles, while the 486 does so if it feels like it (e.g. when filling a line of the L1 cache). It doesn't matter if a chipset supports the 486-type burst if you install a processor that just never does a burst (like a 386). I can think of just one feature of the 386 bus protocol that's not present in the 486 bus protocol: Address pipelining. I wonder whether all 386/486 combo chipsets include support for 386 address pipelining.

Address pipelining is a 386 feature that allows the chip to output the address of the next bus cycle while the data transfer of the previous cycle is still running, enabling address decoding of a subsequent cycle to be parallelized with handling data transfer of the previous cycle. Allowing this kind of parallelism is adding complexity to the chipset, which will never be used by a 486 processor, which might motivate manufacturers of a 486 chipset with 386 compatibility to just leave it out.

mkarcher wrote on 2024-09-22, 09:30:

As the 386 and the 486 front-side busses are quite similar, having a chipset support both isn't that difficult. Obviously, the 386 does not do burst cycles, while the 486 does so if it feels like it (e.g. when filling a line of the L1 cache). It doesn't matter if a chipset supports the 486-type burst if you install a processor that just never does a burst (like a 386). I can think of just one feature of the 386 bus protocol that's not present in the 486 bus protocol: Address pipelining. I wonder whether all 386/486 combo chipsets include support for 386 address pipelining.

Address pipelining is a 386 feature that allows the chip to output the address of the next bus cycle while the data transfer of the previous cycle is still running, enabling address decoding of a subsequent cycle to be parallelized with handling data transfer of the previous cycle. Allowing this kind of parallelism is adding complexity to the chipset, which will never be used by a 486 processor, which might motivate manufacturers of a 486 chipset with 386 compatibility to just leave it out.

So is having 386/486 chipset isn't bad?

Tiido wrote on 2024-09-22, 02:26:

I'm of the opinion that best 386 chipset is a 486 chipset, you get proper support for the Cyrix CPUs with internal cache. Performance of 486 chipsets is usually better too and you get more out the 386 than otherwise.

But then, why not upgrade the CPU to 486? You basically opt for an early Celeron, so to speak.

it is more about letting the 386 reach its limits rather than be held back by stuff outside it, it may be the celeron compared to 486 but that is fine.

The good true 386 chipsets had better main memory thoughtput, while the hybrid ones tended to have better external cache design.
Things kind of even out with regards to overall performance. The hybrid boards have the advantage of almost always supporting the 40mhz bus, 4mb SIMMs and cyrix support.

daniil1909 wrote on 2024-09-22, 11:00:

So is having 386/486 chipset isn't bad?

Of course using a 386/486 chipset for a 386 CPU would be ok. What is making you think otherwise?

Somewhere in my stocks-o-crap have a Opti 495sx based ISA 386/486 board with a 486DX2-66. Never considered putting a 386 on it (nothing soldered in PQFP area, is bare).....
Is a version of this board: https://theretroweb.com/motherboards/s/artek- … 5-sx-cache#docs
I have the paper manual and remember telling Deksor and Evasive I would scan it sometime, the one TRW has (not the MTL) but the other is missing some info from mine...I been lazy and haven't yet 🙁
edit: pasted wrong link, fixed ;/ and looks like this one: https://theretroweb.com/motherboards/s/auva-c … -tam33-40#chips as do many clone Opti 495sx based

Anonymous Coward wrote on 2024-09-23, 00:14:

The good true 386 chipsets had better main memory thoughtput, while the hybrid ones tended to have better external cache design.
Things kind of even out with regards to overall performance. The hybrid boards have the advantage of almost always supporting the 40mhz bus, 4mb SIMMs and cyrix support.

Yeah I was reading about how 386 was supposed to be designed to lock step with RAM such that it was zero wait state, not sure how many mhz that's good for or what nanosecond speed RAM, but seems to imply you don't need a cache if the chipset does it right... unless it all blows up at 33 or 40mhz etc, and that's why you see 40mhz AMDs on 486ey chipsets with a smidgin of cache.

I think 25mhz was the cutoff for 0ws cacheless 386s.
There are some true 386 boards (with chipsets designed specifically for the 386) which were made in late 1992 which have all the bells and whistles of the hybrid boards. These are the most desirable ones in my opinion.

akimmet wrote on 2024-09-23, 00:15:

daniil1909 wrote on 2024-09-22, 11:00:

So is having 386/486 chipset isn't bad?

Of course using a 386/486 chipset for a 386 CPU would be ok. What is making you think otherwise?

I just wondering is theres some advantages of true 386 chipset

Anonymous Coward wrote on 2024-09-23, 10:18:

I think 25mhz was the cutoff for 0ws cacheless 386s.
There are some true 386 boards (with chipsets designed specifically for the 386) which were made in late 1992 which have all the bells and whistles of the hybrid boards. These are the most desirable ones in my opinion.

As i know, dx version was almost 2x higher cost so they put cheap sx version in early 386 motherboards (1990-1992)

daniil1909 wrote on 2024-09-23, 12:27:

akimmet wrote on 2024-09-23, 00:15:

daniil1909 wrote on 2024-09-22, 11:00:

So is having 386/486 chipset isn't bad?

Of course using a 386/486 chipset for a 386 CPU would be ok. What is making you think otherwise?

I just wondering is theres some advantages of true 386 chipset

Also, i seen 90% of 386dx is 1991-1992 so i feel like i own 486 as its 1993 m/b