IBM did not intend the P70 processor to be upgradable, as far as Ihave been able to find out. It's possible that one of the IBM upgradesfor the Model 70/80 may work, but every one that I have seen has not beenusable due to the orientation of the CPU socket in the P70. An IBMupgrade for the 5530 (if such exists) may fit the -031/-121 planar, however.Anyone having more definite info, please let me know.Various aftermarket plug-in 386-to-486 CPU-only upgrades should work.I had a Cyrix 386/486 CPU installed for a while, that is pin-compatiblewith the 386DX. It worked fine, although the P70 BIOS did not supportthe write-back L1 cache in the CPU. DON'T enable write-back if youtry this, or you WILL experience hard drive corruption! The increasein performance is nothing to write home about, but if you just need toadd a little speed, it's the most economical way to go. You do needsoftware from Cyrix to enable the internal L1 cache, though. I willbe publishing comparative benchmarks here when I get time to take somedata.Kingston offered two types of486 Now! CPU upgrades (in SX and DX versions) for the P70:486/33PD3-P70 (DX) and486/33PS3-P70 (SX) for the 38F4688/65X1564 planar used in the 20 MHz -061model.486/33PD3-P70LP (DX)and 486/33PS3-P70LP (SX) for the 38F6973/56F9085 planar used in the 16MHz -031 and 20 MHz -121 models.(Photos are Copyright 1993, KingstonTechnology Corp.)Note that I have also seen the 20 MHz -061 planar used in the -121 model.It is important that you get the right model for your planar, as the orientationof the CPU socket is different and the upgrade will not physically fitif it is not the correct one.Fellow PS/2'er Karsten Harderwas kind enough to send me a 486/33PD3-P70LP fitted with an AMD 486DX-40CPU from the factory (thanks, Karsten!). Installation was simpleand straightforward, and nicely documented in the Kingston manual.If the planar is fitted with a 387DX math coprocessor, it must be removed(even if you only have the SX upgrade). After properly setting thefour DIP switches, the machine booted and seemed to run fine (althoughit seemed to take much longer to initialize the POST routines on power-up).I see no reason why clock doubled or tripled CPU's could not be used withthis upgrade, space inside the P70 permitting. I did test the upgradewith an Intel 486DX4ODPR-100; it came up fine, and benchmarksreported a CPU speed of 120 MHz. Be careful when removing the CPUfrom the circuit board; the Kingston board is quite thin, and is very susceptibleto damage. The DX4ODPR is tall enough that the heatsink will prohibitthe use of a long card adapter in the 32-bit MCA slot, however. TheSX version should accept a DX CPU without trouble. The downside:you are still using the slow (by comparison) planar memory. The lackof L2 cache also hinders performance. Still, it is a worthwhile upgradeif you can't find a MCMaster card.The best performing CPU upgrade for the P70, by far, is the Kingston/AOXMCMaster 486 cards. My machine is currently running with a 25 MHzMCMaster that I managed to overclock to 32 MHz (yes, 32 MHz, not 33).See FredSpencer's page for the info on how I accomplished this. Interestingly,the only CPU that would run reliably with a 32 MHz base clock on this boardis an IBM (Cyrix) Blue Lightning DX4-100. An Intel DX2-66ODPR andan AMD 5x86-P75ADZ (with interposer) would both lock up after a randomperiod of time running Windows. The problem did not appear relatedto cooling, so my conclusion is that some of the components on the cardare slightly speed sensitive. I would be interested in hearingfrom anyone who has successfully used clock-multiplier CPU's on a true33 MHz MCMaster. As mentioned above, I hadto disable the planar memory in the MCMaster setup, as the machine wouldgenerally refuse to boot once the MCMaster took over. Disadvantagesof the MCMaster upgrade: actually finding one, although they do seem toshow up on eBay occasionally (surplusauctions are also a good source, it's a good bet that any university orgovernment agency that bought a lot of PS/2's will have a few floatingaround); it takes the only 32-bit full-length MCA slot, which limitsyour options for adding other cards; and you need a CPU heatsinkwithout a fan, because there simply isn't enough room for a fan.This shouldn't be a problem, as cooling seems to be adequate for a CPUwith heatsink only.My little P70 (a.k.a. "Punkzilla , fastest P70 in the west")is currently running the MCMaster with the IBM DX4-100 CPU and 24 MB ofRAM, and runs PC-DOS 2000 and Windows for Workgroups 3.11 very well.I have a 3Com Etherlink III network card (with the blue handle removed)in the 16-bit slot, and it barely fits. I have the computer set upto track Ham Radio satellites with LogsatProfessional 5.1, and it has come in handy as a portable satellitetracking computer. I've got an AUI transciever for the network cardso I can connect to either coax or twisted-pair networks, and have usedthe machine with both NETBUI (Windows) and Novell networks. The transcieverand the reference disk fit neatly inside the I/O cover, and all I needis to run the reference disk to tell the network card which port I wantto use. These upgrade attempts have successfully turned what somewould consider a slow, old dinosaur into a very usable machine for servicework, portable word-processing or database functions, or just about anyother use you can come up with. Add a decent-sized SCSI hard diskwith a Future Domain MCS-700 controller (at the expense of losing the networkcard), and it would probably even run Windows 95 comfortably (not thatI would actually WANT to...).
Capitalism Plus Portable Edition
2ff7e9595c
댓글