AlessandroB wrote on 2023-01-09, 21:08:

it's time to investigate some model, it must work on VLB, boot from Hard disk and CD-Rom. It would be used on DOS 6.22, Win3.11 and maybe experiment on OS/2, WinNT etc, but those two things are secondary. It would be used on busses maxing out at 33Mhz. What model could I get? Do these requests require any particular support from the PC bios? I didn't see "SCSI" written in the boot options for example...

Thank you

Adaptec 284x are standard for VLB SCSI.
Some BusLogic and Tekram are nice compatible too.
They are bootable if you set IDE disks to “none” in your BIOS or change boot order from C/A or A/C to “none” too. In this case BIOS deligate boot procedure to opt. ROM BIOS extension of your SCSI card.

Babasha wrote on 2023-01-09, 21:24:

Adaptec 284x are standard for VLB SCSI. Some BusLogic and Tekram are nice compatible too. They are bootable if you set IDE disk […]
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AlessandroB wrote on 2023-01-09, 21:08:

it's time to investigate some model, it must work on VLB, boot from Hard disk and CD-Rom. It would be used on DOS 6.22, Win3.11 and maybe experiment on OS/2, WinNT etc, but those two things are secondary. It would be used on busses maxing out at 33Mhz. What model could I get? Do these requests require any particular support from the PC bios? I didn't see "SCSI" written in the boot options for example...

Thank you

Adaptec 284x are standard for VLB SCSI.
Some BusLogic and Tekram are nice compatible too.
They are bootable if you set IDE disks to “none” in your BIOS or change boot order from C/A or A/C to “none” too. In this case BIOS deligate boot procedure to opt. ROM BIOS extension of your SCSI card.

ok thanks and in this case then from the bios of the scsi controller I select if I want to boot from the hard disk or from the CD-Rom? what if you want to install windows95/98? the CD-ROM is bootable but the bios of the PC for example does not allow me to boot and I have to use the floppy, with the 2840 controller how does this procedure work? And what about the hard disk size limite of this controller?

AlessandroB wrote on 2023-01-09, 21:32:

ok thanks and in this case then from the bios of the scsi controller I select if I want to boot from the hard disk or from the CD-Rom? what if you want to install windows95/98? the CD-ROM is bootable but the bios of the PC for example does not allow me to boot and I have to use the floppy, with the 2840 controller how does this procedure work? And what about the hard disk size limite of this controller?

I don't expect that these controllers can boot from CD. But you may use aspi7dos.sys + aspicd.sys + mscdex.exe on a boot disk.
The 284x from Adaptec do have an 8 GB Limit.

However, mkarcher patched those (and the 274x for EISA too) to overcome the 8 GB limit. Please note that you need to use the patched aspi7dos.sys too.
INT13 Extensions to Adaptec 274x EISA & 284x VLB
Full story:
Showing some love for Adaptec's ugly ducklings: Adding big drive support to EISA and VL controllers

Note: Please don't expect too much out of the 284x VL. It seems that adaptec had converted the (real good) 274x EISA to be used on a VL. But I do not understand where they have lost the performance of such an outstanding controller.
274xW: 18 MB/s (EISA), 274x: 9 MB/s (EISA), 284x VL: 6 MB/s

Win9x & WinNT drivers do not have a problem with the 8 GB limit.

what about this instead?

https://www.ebay.it/itm/143990936607?mkcid=16 … emis&media=COPY

Disruptor wrote on 2023-01-10, 06:24:

I don't expect that these controllers can boot from CD. But you may use aspi7dos.sys + aspicd.sys + mscdex.exe on a boot disk. T […]
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AlessandroB wrote on 2023-01-09, 21:32:

ok thanks and in this case then from the bios of the scsi controller I select if I want to boot from the hard disk or from the CD-Rom? what if you want to install windows95/98? the CD-ROM is bootable but the bios of the PC for example does not allow me to boot and I have to use the floppy, with the 2840 controller how does this procedure work? And what about the hard disk size limite of this controller?

I don't expect that these controllers can boot from CD. But you may use aspi7dos.sys + aspicd.sys + mscdex.exe on a boot disk.
The 284x from Adaptec do have an 8 GB Limit.

However, mkarcher patched those (and the 274x for EISA too) to overcome the 8 GB limit. Please note that you need to use the patched aspi7dos.sys too.
INT13 Extensions to Adaptec 274x EISA & 284x VLB

Note: Please don't expect too much out of the 284x VL. It seems that adaptec had converted the (real good) 274x EISA to be used on a VL. But I do not understand where they have lost the performance of such an outstanding controller.
274xW: 18 MB/s (EISA), 274x: 9 MB/s (EISA), 284x VL: 6 MB/s

Win9x & WinNT drivers do not have a problem with the 8 GB limit.

it is true that it seems to be slow as a controller, at least in the sequential transfer. On the other hand, in real use, between the shorter access times and the lower cpu occupation, shouldn't the computer be more snappy all the same? How much do you think my stock ide controller could do in the transfer rate?

This depends on operating system, used software and access patterns.

Disruptor wrote on 2023-01-10, 06:52:

This depends on operating system, used software and access patterns.

Basically is a DOS + win3.11 machine but i can experiment on win95, WinNT or os/2 but very very little.

As with so many things, you can look at this in a purely theoretical point of view, but unless you have access to all possible cards and/or unlimited money to buy anything, then it makes a lot more sense to see which VLB SCSI adapters you can actually find/afford and then look how suitable they are for your purposes.

Pretty much anything from VLB era will support DOS, Win3.x and OS/2, most will work fine under WIn95 and NT as well, so unless you find something really obscure it will probably work.

Benchmarking/reviewing was so primitive in the day (at best a deepdive into one very specific use case/application, invariably either NT or Unix-based for hardware like this) I wouldn't put a huge amount of trust into "card X is faster" or "chip Y is faster" statements. If you find the motherlode of VLB SCSI cards it would be very interesting to do a comparative benchmark. It wouldn't surprise me to see similar results as with VLB VGA: where under Windows (NT) acceleration features determine performance, under DOS it's just a matter of efficient bandwidths - and the simplest solutions perform best.

This is basically how my hard disk work on my system. it is an original IBM 1,2GB disk drive, seems a bit slower to me...