I have come to terms with the fact that a IIFX or Quadra 840AV is not going to fall out of the sky for me. I have decided on a IIsi because I like the pizza box form factor but I do not like the limitations of the LC series. According to a post I read on here, it seems I can even cut a hole in the top to pass a SCSI cable through and attach a CDROM Drive without having to purchase an external based unit. It works with Rominator II. Are there any technical caveats or gotchas that I should watch out for specific to this machine? I already know to look for PRAM batteries that have exploded.
-
Updated 2023-07-12: Hello, Guest! Welcome back, and be sure to check out this follow-up post about our outage a week or so ago.
Any known caveats with a IIsi?
- Thread starter Nifty950
- Start date
3lectr1cPPC
Well-known member
Bad motherboard caps as one would expect, but the power supplies are garbage in these. Leaky through hole caps, but they also have an internal soft power board with surface mount cans. Once you get one recapped and booting, it should run forever, but it’s a rough road to get there.
Other than that they’re good systems - just one thing you should know. The IIsi uses the motherboard RAM as VRAM, and the motherboard RAM is slower because of this. For best performance out of one of these, you‘ll want all your programs running off of ram SIMMs. I forget exactly how to do this (maybe increasing the disk cache to eat up the slower motherboard ram? Not sure). I believe people call this “vampire video”. Again, I don’t know a lot about this, but I don’t believe it affects things that much.
Overall a solid Mac, if you can get it working.
Other than that they’re good systems - just one thing you should know. The IIsi uses the motherboard RAM as VRAM, and the motherboard RAM is slower because of this. For best performance out of one of these, you‘ll want all your programs running off of ram SIMMs. I forget exactly how to do this (maybe increasing the disk cache to eat up the slower motherboard ram? Not sure). I believe people call this “vampire video”. Again, I don’t know a lot about this, but I don’t believe it affects things that much.
Overall a solid Mac, if you can get it working.
cheesestraws
Well-known member
You could either pass it through the hole for expansion cards in the back or you can get a little adapter PCB to convert between internal and external SCSI. No need to cut a hole in the case
.Are you saying the soft power board is internal to the power supply? As in take the power supply apart?
jeremywork
Well-known member
Precisely. Setting a disk cache of 768k+ eats the remainder of the "slow" 1MB bank used for VRAM (up to 320k when in 256 colors.) The IIsi and IIci are both set up this way, but the IIci has its first bank in traditional 30-pin SIMM slots. Ideally you'd want 4x256k in bank A for the 768+320 to roll you over to bank B. The IIsi's soldered 1MB in bank A saves you the trouble of finding those SIMMs.
mikes-macs
Well-known member
The Mac IIsi is a capable Macintosh and it can support more memory than an LC. They have a clean rom, so you can max the memory at 65 MB. Expandability other than that is limited as there is only 1 PDS slot. If you are going to want to expand it the type of expandability lies in the direction of Network Adapters and Video Adapters and can be done with a PDS/Nubus adapter, sometimes gaining an FPU in the process. These adapters are hard to come by and expensive. The Mac IIci has more expandability. Just be careful because as mentioned, they all need to be recapped including the power supply. If you're able to do that kind of work then great. Otherwise you'll pay shipping and service cost to have it working correctly. "IIsi Ram Muncher" also did the trick to take care of the video ram issue mentioned above.
The internal display capability is 640x480 at 8 bit.
The internal display capability is 640x480 at 8 bit.
mikes-macs
Well-known member
Also, please don't cut a hole on the case because you'll disrupt the airflow inside the case as it runs. External CD ROM options are not expensive at all.
Are we really concerned with airflow? Its a 68k not exactly a race horse here. But no, there will be no hole cutting in my 300 dollar machine. I plan on finding one of thoes caddy loading drives they are so freakin cool!
Wait is the IIci better? Its got that boxy quadra 700 style case. not sure if i like it.
mikes-macs
Well-known member
I feel so much better knowing you are not going to cut the case. Airflow was the only thing I could think of to deter you.
jeremywork
Well-known member
You trade one PDS slot for three Nubus slots. 030 PDS is faster but a bit more bespoke and more difficult to find cache/accelerator+passthrough adapters for, if that's your thing. The IIci's cache slot is easy to find cache for, and accelerators fit without adapters. They're mostly the same thing technically, but the IIsi is running at 20MHz from factory, though completely capable of being oscillator swapped to run at 25MHz like the IIci. Also, if you don't mind paying a speed penalty, you can populate more RAM in bank A to exceed 65MB (up to 128MB.)
I was joking about cutting a hole in it. I can only imagine you sitting there thinking "this buffoon is going to ruin it!". No, the sheer rarity of these things is what deters me. I by no means plan on keeping it original, its going to get all sorts of upgrades but im not cutting up anything.
I dont think 5mhz makes much difference, and I like the IIsi case way better. I'll take my chances.
jeremywork
Well-known member
It's a 25% overclock (or factory underclock, really.)
Same as a Q6600 overclocked to 3GHz.
An 840AV running at it's true max of 45Mhz would only be 12.5%, and a Daystar PowerPro with RAM at it's true max of 85MHz would only be 6.25%
Percentages trump MHz.
Same as a Q6600 overclocked to 3GHz.
An 840AV running at it's true max of 45Mhz would only be 12.5%, and a Daystar PowerPro with RAM at it's true max of 85MHz would only be 6.25%
Percentages trump MHz.
provided sufficient cooling, whats the fastest we can get a IIsi (so do we say it twosie?) to run at
jeremywork
Well-known member
Speculation is that the IIsi nearly shipped at 25MHz, but was underclocked to keep the IIci at a higher market position. Low End Mac thinks 27.5MHz *should* work, but take that with a grain of salt. Back in 2013, uniserver clocked one successfully at 29MHz, but had trouble using PDS NIC and booting from floppy in this config:
50% faster graphics Mac IIsi, Overclocking?
http://macvintage.tripod.com/iisi/overclock.html i know the graphics is kinda sluggish, setting disk cache to 1024K does help! but would changing the oscillator from 40 mhz --> 50 mhz +5mhz Speed it up to where i would notice? Because i was considering taking the 50mhz Oscillator from my...
68kmla.org
Edit: forgot to mention above on IIci v IIsi, the IIci has an onboard FPU, while the IIsi can have one added via PDS. That said, most common PDS adapters for cache, ethernet, etc also contain an FPU socket, so shouldn't be too hard if you want one.
3lectr1cPPC
Well-known member
Since you've found one recapped already this shouldn't be an issue, but yes, it is inside the power supply. It's also vertically mounted so that goo can easily get under an IC on that same board, causing all sorts of issues. Good thing you're avoiding all that.Edit: found the one you were talking about.
Similar threads
