I'm unable to give up DOS CD-ROM access. It's too inconvenient for those later games with disc checking.

To be clear, I'm not overclocking the UMC IDE controller. I am running it at 33 MHz. If it's run at even 40 MHz, the UMC DOS driver won't load w/Cyrix 5x86.

It would be interesting to see if CF cards supporting block mode, or multi-sector transfers, suffer the same fate on the UMC IDE controller. So far, I haven't run across such a CF card, but Mouser sells them for around $300 for an 8 GB card. Other than seek, late era mechanical HDDs, usually from about 2006 or later, offer similar or slightly better throughput to CF cards. There are USB 3.0 to IDE adaptors available now which would make cloning more convenient. I'm using a USB 2.0 to IDE adaptor now and its way too slow for cloning with dd.

I picked up a handful of 8gb innodisk iCF 4000’s on the cheap that support max block transfer size of 2. Enabling block transfer modes showed no real improvement in ISA or VLB for them . As a warning, the CF’s are so slow on PIO work loads that they are unpleasant to use. They had locked copies of Win XP imbedded installed on them with some sort of industrial app so the look like they are legit. With UDMA, they can rise to the level of “slightly disappointing”.

douglar wrote on Today, 00:07:

I picked up a handful of 8gb innodisk iCF 4000’s on the cheap that support max block transfer size of 2. Enabling block transfer modes showed no real improvement in ISA or VLB for them . As a warning, the CF’s are so slow on PIO work loads that they are unpleasant to use. They had locked copies of Win XP imbedded installed on them with some sort of industrial app so the look like they are legit. With UDMA, they can rise to the level of “slightly disappointing”.

Do we have any idea how the Innodisk iCF 4000's compares to the Innodisk iCF 1SE3 series? e.g. https://www.mouser.ca/ProductDetail/Innodisk/ … eKIw4x4vw%3D%3D

The spec sheet for the 1SE3 leaves much to be desired in terms of specifics, but it does list "max channels: 2", which I assume is the block size. If each sector is 512 bytes, then its only transferring 2x512 byte per interrupt. Typical harddrives do 16 or 32 sectors per I/O, and later models have 8+ MB of cache onboard.

For the case of the UUD w/onboard IDE and CF at 33 MHz, wouldn't the interrupt need to be triggered more often compared to a modern HDD with block mode? The selective crashing with DRAM at 1 ws is likely due to the memory controller and I/O subsystem not being able to cope with the frequency of interrupt requests, rather than the IDE being faulty, that is, since switching to 2 ws is flawless. .. or using 1 ws with DiamondMax 10 IDE, which is flawless.