Jo22 wrote on 2022-07-21, 10:27:

rasz_pl wrote on 2022-07-21, 05:51:

16bit ISA is around 5MB/s.

At 8,33 MHz ("ISA").
That number is from vcfed, I suppose. 😉

I meant thats the number fastest ISA VGAs reach on overclocked bus. I dont remember ever seeing one passing 6MB/s. Thats with rep movsw, port IO would probably top out lower.

pshipkov wrote on 2022-07-20, 19:25:

It is implied that for ISA bus we are talking Adaptec AHA-1542CF.

I was a SCSI guy back in the ISA era, and yeah, Adaptec 1542 is the go-to. It's bootable, DMA-capable (although ISA DMA can be twitchy), and supported by anything SCSI from that era.

I would like to specify the question further:

Most 386 boards do only support pio mode 0 which allows 3,3MB/s per definition.

I wonder whether this limitation also „grows“ by increasing isa Bus Speed. Sorry I don’t wonder but my tests show „yes“ 😀

My question here is: would an Isa 386 system with overclocked Isa and very modern HDD also benefit from PIO mode 3 or higher? Keep in mind that higher PiO modes also reduce minimum cycle time dramatically.

Are there any ide controllers for isa providing these modes? I couldn’t find any.

Thanks.

My understanding is that ISA IDE controllers implement PIO-0 mode. Never saw one that offers an adjustable PIO cycle time.
Even if such thing existed it will be capped by the ISA bus, especially when operated within the standard 8-12MHz.
So, the answer to your second question is - potentially yes, but under the condition of overclocking the ISA bus high enough to be able to take advantage of the tighter PIO cycle timing, otherwise the controller will be waiting for the ISA bus to come around.
You may be interested in checking this post which offers relevant information.

Thanks a lot - also for this fantastic link.

I think some SCSI support DMA which seems to be working on this system?

Anyway, that’s why I ended up going with SCSI it’s working good!

I shared some Benchmarks here comparing scsi on a 1542c plus Zulu or HDD vs late eide devices. The crown always went to ide there at the end.

Ja strange. After reading whole thread I couldn’t find / identify any isa card with higher PIO modes. At least not mentioned in particular.

It is like it is 😀 thanks

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