X-Git-Url: https://git.draconx.ca/gitweb/homepage.git/blobdiff_plain/c047dafad7bcb66a096284497eca6ef20ca1584d..eb8b04d03e5355826a8e4e53274faf24d2320cd3:/content/weblog/ultra60-nvram.md diff --git a/content/weblog/ultra60-nvram.md b/content/weblog/ultra60-nvram.md new file mode 100644 index 0000000..ec96370 --- /dev/null +++ b/content/weblog/ultra60-nvram.md @@ -0,0 +1,101 @@ +--- +title: M48T59Y-70PC1 NVRAM Battery Replacement +copyright: 2022 Nick Bowler +license: cc-by-sa-4.0 +published: 2022-07-09T12:12:21-0400 +--- + +*[NVRAM]: Non-Volatile Random Access Memory +*[SRAM]: Static Random-Access Memory +*[NOS]: New Old Stock +*[DIP]: Dual In-line Package +*[SOIC]: Small-Outline Integrated Circuit +*[MAC]: Media Access Control + +Thanks to [Mark Henderson's Sun NVRAM FAQ][nvram-faq] for providing invaluable +insight regarding this repair. +{:article-info="article-info"} + +[nvram-faq]: http://web.archive.org/web/20150919135835/http://www.squirrel.com/sun-nvram-hostid.faq.html + +The Sun Ultra 60 workstation uses an ST M48T59Y-70PC1 battery-backed SRAM with +real-time clock. When the embedded lithium primary cell inevitably dies, the +chip is essentially useless. The most noticeable negative effect of a dead +chip is that the workstation always powers up in a default configuration with +diag-switch? true, running several minutes of self tests every time, with +bogus MAC and host ID values. + +<%= floating_img(@items["/images/m48t59y.jpg"], caption: < + +This device was branded obsolescent by the manufacturer in April of 2008 and +has presumably been out of production since around that time. Similar chips +like the M48T58Y are still made but they are expensive (around $40) and slight +differences may result in compatibility problems. It appears that NOS parts +can be found fairly cheap online but these must be almost 15 years old by now +and who knows what state the embedded batteries are in. No thanks. + +One option could be to find the SOIC version of the M48T59Y for which NOS also +seems to be available, although somewhat less readily than the DIP modules, and +then construct an adapter board to fit into the DIP socket on the motherboard. +The SOIC package does not include the battery and crystal; instead, it has +contacts on the top to attach a separate "SNAPHAT" package which are still +made. This would be complicated and somewhat expensive. + +Fortunately, a straightforward (if time-consuming) repair is possible. This +is a literal hackjob: we can dig through the potting to expose the battery +terminals, disconnect the internal battery, and connect a normal battery clip. +This enables the use of readily-available CR2032 lithium primary cells that can +be replaced as needed, just like a normal PC. Since we already have the chip +we need, it is not necessary to source any obscure or expensive components. + +<%= +floating_img(@items["/images/m48t59y-terminals.jpg"], left: 1, caption: '') +%> + +<%= +floating_img(@items["/images/m48t59y-solder.jpg"], left: 1, caption: '') +%> + +The battery contacts are located on the end opposite pin 1, between pins +14 and 15. Looking underneath the chip there is a small well at either end +filled with potting compound. The battery connections are inside one of +these. Using a knife, cut back the plastic outer shell on the battery side, +then begin scraping away potting compound until the terminals are exposed. +You can use a suitable DIP socket to help protect the pins from accidental +damage. + +Once the terminals are exposed, the internal battery must be disconnected. +The thick protruding tabs near the bottom of the module are what we want +to solder to. The vertical strips going up and into the module are the +internal battery terminals. These can be desoldered from the tabs and +lifted out of the way, or simply cut off. + +With the time-consuming parts completed it is a straightforward matter to +connect a normal battery clip to the exposed terminals. As the Ultra 60 has +no clearance issues I simply glued it to the top of the chip. Since this +would obscure the barcode sticker which is useful to restore the original MAC +address and host ID, I moved this sticker to the side of the chip. + +Finally all that remains is to put everything back together and power up +the system. The system will run the full self-diagnostic tests again and +if all goes well, the "NVRAM Battery Detect Test" should no longer display +any errors. At the ok prompt, the memory can now be initialized. Where +"AA BB CC" are the six hexadecimal digits from the orange barcode sticker: + +set-defaults
+setenv diag-switch? false
+8 0 20 AA BB CC AABBCC mkpl
<Ctrl-D><Ctrl-R>
+.idprom
+reset + +<%= gallery_img(@items["/images/m48t59y-fixed.jpg"], caption: < +<%= gallery_img(@items["/images/m48t59y-installed.jpg"], caption: <