can you tell me how you benchmarked your SCSI system to reach a speed of 32,000 KB/s? I would like to run a comparitive test on a 486 with IDE, to see how far behind it is.

I tend to get 37000 KB/S with a 40 MHz FSB.

Well, I used a SCSI-specific Windows benchmark program from Adaptec (EZ-SCSI). I've noticed that NT4.0 usually puts its IDE hardware as SCSI, so I may be able to test out the CF/IDE benchmark. Its on my list. There are also other benchmark programs. Here are some scores I got in the past on a 33 MHz FSB:

WinTune98, CacheDisk Score = 18.3
WinBen96, DiskMark = 743
Sandra2002, FileSystem = 16006 (20210 for 40 MHz FSB)

I have a PCI-SATA/ATA33 controller (UDMA) known to work well on a 486 so I can test this vs. PIO4 on a 486 and compare it to the SCSI. I have this controller listed in the World's Fastest 486 thread. I'll need to get a parallel installation going, which I don't have time for at the moment. I'm going on holiday for a month shortly.

I don't have any ATA66, ATA100, or ATA133 controllers to test out but am fairly confident that even an UltraWide (40 MB/s) on a 486 will run faster than all of these. I use an Ultra2-LVD (80 MB/s) controller. There was a time when I installed Windows on a PIO3/4 system; it took about 4x as long and, once installed, the system felt slower than slow compared to the same hardware on an Ultra2-LVD SCSI system.

If you are insistent on using a CF card, and want the processing power of SCSI, you might want to consider a CF/IDE-to-SCSI microcontroller converter. ACARD makes them. Unfortunately, I haven't been able to find any reasonably priced ones recently. $130 new, and there's a similar unit on eBay for $135.

If the reason for the CF is quiet operation, not all SCSI disks are loud. Modern ones are as quiet as new SATA drives. I've listed one the World's Fastest 486 Specs that is 137 GB and very quiet. That is another benefit of SCSI, you can use large hard drives without software intervention. Theoretically, an Adaptec 2940U2W (the one I'm using) has a max capability of 2TB. I've been wanting to test some 2 TB SATA drives on it via a SATA-to-SCSI converter.

One last thing about SCSI, if you use a 2940U2W, it has a second connector for SCSI narrow, so you can attach your bootable DVD-ROM drives and boot from disk without having to go into DOS. For me, SCSI vs. non-SCSI on a 486 is a no brainer.

EDIT: For fun I just did a quick Win98SE install on a PIO-4 IDE/CF drive. To say the least, it was a big test in patience compared to installing it with the above mentioned SCSI interface.

Thanks a lot for the excellent info!

feipoa wrote:

...
For me, SCSI vs. non-SCSI on a 486 is a no brainer.

And I see what you mean about the no brainer part. BTW, CF devices come in different speeds. What speed is yours?

133X, 8 GB. 8 GB for guaranteed BIOS compatability.

133X is rated for ~20,000 KB/s.
PIO-4 is rated at ~17,100 KB/s.

Under normal operating conditions, I doubt that any 486 can do 17,100 KB/s under PIO mode, however the SCSI benchmarks shown already do twice that on a 486.

@5u3
Does your Asus PVI-486SP3 BIOS allow for L2 write-through mode at all?

feipoa wrote:

😎 Since it has a SiS chipset, I assume it works with some graphics cards more modern than a Matrox G200. What is the most modern graphics card that you've been able to run in here? Voodoo3, Voodoo2, nVidia Riva TNT2 64?

I have the same board and use a Riva128 with it. However, I'm trying to find a video card with DVI that actually works 🙁

Have you tried the Matrox G450 PCI for DVI support? From way back, I remember that it only works with Intel-chipset boards, so an Asus PVI-486AP4 may work if you have this board. I've never had this motherboard to test myself.

feipoa wrote:

@5u3
Does your Asus PVI-486SP3 BIOS allow for L2 write-through mode at all?

Yes, the L2 cache can be toggled between write-through and write-back in the BIOS setup.

So, uh...what are the differences between Award Bios 4.50g and 4.51g? Differences in tabular columns will be helpful.

The differences so far are only speculative, as was witnessed above. The differences are still an open question. Maybe when I get my retro itch back I'll take a closer look.

The Biostar MB-8433UUD v3.0 may be a good platform to test out these differences as it is flashable with both AWARD BIOS v4.51PG (96/05/20) and v4.50PG (96/03/26).

feipoa wrote on 2011-07-10, 03:25:

The differences so far are only speculative, as was witnessed above. The differences are still an open question. Maybe when I get my retro itch back I'll take a closer look.

The Biostar MB-8433UUD v3.0 may be a good platform to test out these differences as it is flashable with both AWARD BIOS v4.51PG (96/05/20) and v4.50PG (96/03/26).

Meanwhile, somewhere in the past 15 years (heh) this appeared on the internet: https://www.dosdays.co.uk/topics/bios_award.php

It sounds as if boot from CD has been added from 4.50->4.51, although "your miles may vary" still applies.

The Asus VL/I486SV2GX4 seems to have gotten a 4.51 update in 1997: https://theretroweb.com/motherboards/s/asus-vl-i-486sv2gx4

I intend to try it out on mine some time in the future (no rom programmer situation) but if somebody else with one of these boards (they are popular) beat me to it we would like to know 😀

I have never run into a socket 3 motherboard which had IDE CD-ROM boot support, nor LS-120 boot support. This ability appears with many socket 5/7 boards. Maybe CD-ROM boot-abilty is more than just BIOS version support; perhaps it is also related to the IDE controller?

Neither have I seen a 486 board that can, but since it is a 1997 update I thought there might be a chance.

After all, these bioses are very modular. Perhaps it is more a question of whether the features all fit into the target image size to make the cut or not. It raises the question if a 4.51 bios with all new 4.51 features cut still qualifies as a 4.51... I think version control in bioses was a nightmare.

I do not think the IDE controller plays a major role, as some socket 5/7 boards have a chipset based PCI controller for the primary channel, but a dumb ISA implementation for the secondary, and they can boot cdrom off of the secondary.

feipoa wrote on 2026-04-17, 12:53:

I have never run into a socket 3 motherboard which had IDE CD-ROM boot support, nor LS-120 boot support. This ability appears with many socket 5/7 boards. Maybe CD-ROM boot-abilty is more than just BIOS version support; perhaps it is also related to the IDE controller?

I'd consider that to be highly doubtful, it being related to the controller.
I'm certain it's just a bios issue.
What st31276a says, the available space in the bios eprom plays a major role.
Which makes me wonder, what is the earliest MrBios rom that supports cdrom boot ? Maybe a question for another thread. 😀

edit: digging deeper, bootable cdrom "el torito" seems to have only started late '94, formally early 1995, which I guess puts it right in the pentium I territory.

If it is only a question of EEPROM size, that would be great. But weren't late socket 3 BIOS sizes the same as early socket 5/7 BIOSES, that is, 1 Mbit?

feipoa wrote on 2026-04-17, 20:53:

If it is only a question of EEPROM size, that would be great. But weren't late socket 3 BIOS sizes the same as early socket 5/7 BIOSES, that is, 1 Mbit?

They are 128KB, yes.
There is no hardware limitation, because bootloaders like SmartBootManager and PLOP that you can run from a floppy can in turn boot from CD-ROM.
As you point out, CD-ROM support tends to come along with LS-120 support. And I've also noticed, oftentimes in Award it seems related to A,C vs. A,C,SCSI as well, which in turn I believe is related to the Intel BIOS Boot Specification: https://www.scs.stanford.edu/nyu/04fa/lab/specsbbs101.pdf

My suspicion is that adding CD-ROM support requires reassembling/recompiling the chipset-specific part of the Award BIOS for some reason, and Award didn't feel like doing that on aging 486 chipsets despite bumping the version number to 4.51 in this small handful of BIOSes.

If I remember right I believe the APC Predator 747 board--the industrial one with the CS4041 chipset where unfortunately the minimum DRAM wait state option does not work--has CD-ROM boot support because the AMIBIOS on it is modern compared to a typical 486.
The ESA 486 industrial motherboard has a modern Phoenix BIOS and can do it too.

It would be nice if someone found a way to augment existing socket 3 BIOSes with CD-ROM boot support, particularly for SiS 496 and UM8881 based boards. Were there some socket 4 or 5 boards based on the UM8881/8886 chipset? Perhaps those AWARD BIOSes have already done this leg work?