Oldskooler Ramblings

I’ve added a CompactFlash II memory card to my XT. And it was surprisingly easy, cheap and fast! Since CompactFlash essentially follows the IDE spec, you can get gaggles of CF-to-IDE adapters from ebay for single-digit dollars, including shipping. I grabbed one, stuck an IBM Microdrive 320MB CFII card into it, and now my XT has a giant (for an XT) second hard drive on this tiny little card!

(Confession: I lied about the “easy” part. It’s very easy to physically attach the thing to the cable… it’s incredibly difficult to find an IDE adapter that works in an 8-bit ISA slot. I lucked out and found a Silicon Computer adapter (ADP50, I believe) online somewhere for cheap, but they’re incredibly uncommon.)

So, how are the benchmarks against the actual Maxtor 340MB drive that’s also in the machine? Spinrite sez:

• Maxtor 340MB, circa 1994:
  • Average Seek: 18ms
  • Sustained transfer rate: 321KB/s
• IBM CompactFlashII Microdrive, 320MB, circa 2002:
  • Average Seek: 25ms
  • Sustained transfer rate: 322KB/s

Well, I think it’s obvious both drives can go much faster; it’s the 8-bit ISA interface that is holding them back. Still, that’s incredibly fast hard drive access for an XT; the only faster times I know of have been obtained by my friend Michael Brutman, who has SCSI boards in his machine. SCSI isn’t a faster disk technology, but the interface boards sure are (they are memory-mapped, which means disk transfers go right into system memory, as opposed to traditionally being stored/moved by the DMA controller.)

Should you do this with any CF card you have lying around? Yes… but only if you aren’t going to write to it often. Flash is only guaranteed for something between 10,000 to 100,000 writes, then it starts to disintegrate. The only exceptions I know of are IBM Microdrives, because they’re not actually Flash memory at all — they’re tiny hard drives! Read performance is worse than actual Flash, but you can write to them all you like.