Even if the SD card is "slow", you are eliminating head seek time from the equation.
Yeah, I think this badly needs to be kept in perspective when we're talking about vintage applications. Every time I mention I'm a fan of those PATA to SD adapters I cringe knowing the odds are decent that SOMEBODY is going to take it as their cue to
yet again jump into a random thread, hop on a soap box, and start slagging on and on how just simply UNACCEPTABLE low-end flash solutions are for ANYTHING and you have to be an ABSOLUTE MORON to think otherwise... Sigh.
It's positively comical when the subject of the discussion is something like an XTIDE adapter in a 5160-class machine; I mean, for crying out loud the original XT hard disks transferred data at only around 85K a second with IBM's default interleave and had access times in the 80-100ms ball park, and I can testify from using one back in the day: even that was fine. Just absolutely, perfectly fine. When your program binaries are measured in tens or small hundreds of kilobytes even that piddly data transfer rate was enough to get the job done, blew the doors off a floppy. And, of course, even if somehow you had the slowest SD card paired with worst XTIDE adapter ever made not only is your data transfer rate going to be two or three times faster, the access time is going to like
50 times as fast, and that's the thing that's going to really make a difference if you're running something "disk-intensive". (IE, doing more than just loading a binary and running it.) The SD card adapter in my XT-class machine benchmarks effectively the same as an EMS RAMdisk, for heck's sake, it literally goes as fast as the 8-bit ISA bus can go without externally pumped DMA, with
1.4ms access times. Grrrr...
And of course the same objection crops up all the time even if the combination being discussed is something like a Mac Plus and a SCSI2SD. Sorry, the only way to make a Mac Plus' SCSI go fast is fire the computer out of a cannon. SD performance isn't a problem here. Not ever.
People regularly use the HD-20 emulation on devices like the FloppyEMU as full-time hard disks on those machines and don't really notice it's any slower despite using the floppy drive port. (And this sort of makes sense if you're running appropriate software; you're probably not loading more than a few dozen/hundred kilobytes at a time. Access time for the win, again.)
That said, I guess I will admit that better SCSI replacement solutions for
faster computers (post-1995-ish?) are an... under-served area, considering that devices like a SCSI2SD do *technically* max out at raw data transfer rates that really high-end "early-mid-90's", SCSI hard disks could manage. (Vs. the late-90's-ish performance that PATA->SD solutions offer, plus the option of various PATA to SATA/M.2/mSATA/whatever converters which are also widely available and cheap.) But I can sort of understand why no mainstream manufacturer bothers with this stuff anymore; Ultra SCSI was, in the broad scheme of things, a fairly short-lived and high-end niche technology. The sort of applications it was used for don't favor the computer outlasting the drives in "real production" the way more humble applications do. (A dog slow SD adapter or DOM will do just fine, thank you, in that greasy PC that runs your 90's vintage machine tool or whatever.)
