XTs and large hard disks

Wolfe, Julian wrote: IDE with "540MB" (actual capacity is less) drives or less, if you can find an IDE card that works. I have two (different brands) but sadly I haven't found time to try them yet in my model 5150. Only other solution is SCSI, something I have had extremely unlucky progress with (boards with BIOSes won't POST; boards that need drivers don't have the damn drivers bundled with the board; etc.) However, I believe my experience with 8-bit SCSI on XT is uncommon compared with the other gentlemen here. The V20 can enable some ill-behaved programs to work as it implements the "SHL register,immediate" 80186 opcode, and this opcode is sometimes the *only* used opcode used in "286-only" programs. I was able to run programs claiming they needed a 286 on my AT&T PC 6300 (Olivetti M24 8086 clone) after I upgraded it to an NEC V30. HOWEVER, the V20 and V30 expand the prefetch queue from 4 bytes to 6 bytes (the source of their speedup) and this screws with timing-sensitive programs such as games, copy-protected diskette copiers, and turnkey stuff like robot controllers, etc. from the early 1980s. I'm going to go out on a limb and assume that you're expanding your convertable so that it can play most IBM PC games from the 1980s. :-) Based on my experience in that context, the V20 will cause the following behavior compared to a factory original 8088: - 88% of games will run just fine, unaffected by the V20 - 5% of games will run smoother/better due to the small speedup of the V20 - 5% of games will run too fast to be enjoyable - 2% of games will not run at all Games are a good example to flush out this kind of behavior because they were usually programmed as close to the hardware as possible to achieve the best performance; also, many copy-protection schemes are timing-based and may fail if the CPU speed is not what is expected. If I have incorrectly assumed your intentions, please let me know as I'm dying with curiousity :-) -- Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/ Want to help an ambitious games project? http://www.mobygames.com/ Or check out some trippy MindCandy at http://www.mindcandydvd.com/