I have some further updates now I've been using this scope for a couple of days.
Compared to my old Tektronix 2Gsps/200MHz/4ch TDS 2024B 5.7" screen (which has a resolution of 320x240), the 4Gsps/600MHz/4+16ch 54831D 640x480 in 8" is clearly going to be an improvement. I have also added an external monitor which can also act as a touch screen duplicating the main display. It can also be hooked up to extend the desktop to the motherboard display at up to 1280x1024. Because the external 10" monitor is 16:9, and the native VGA ports only support 4:3 resolutions, I've used a DisplayLink USB adapter which supports 1280x720 and sits above the main screen. Surprisingly the DisplayLink adapter takes very little CPU, usually about 1% unles there's a big screen update.
As discussed previously in this thread, the scope app will only run on internal LCD and an external monitor duplicating the 640x480 LCD. It is locked to that graphics card and will not display on the motherboard's VGA port.
So what's the benefit of an external monitor? Well, you can put all the scope app's modeless dialog boxes that would otherwise clutter up your 640x480 main scope screen, and have anything else you choose up there, like the scope help documentation, or a web browser or MS Office for example which won't work very well in 640x480 anyway. Don't expect too much web browsing or videos to work well, Youtube manages about 2 fps on the main screen.
There are three SDRAM slots in there with only two populated up to 512MB. I tried a third today but it wasn't recognised, I think this is a chipset limitation, although it may be BIOS related. I have no intention of updating the BIOS, that sounds like a recipe for disaster.
I'm successfully using a USB keyboard and mouse plugged into one of the two motherboard USB 1.1 ports and the keyboard is recognised by the BIOS.
Using Acronis True Image to make disk images work both over the LAN and through the USB 2.0 card I added, although you have to override the default video probing in my version. To restore an image, I couldn't make it work over the LAN, I had to use a USB 2.0 port.
As a scope, it's a bit of a beast. Yesterday I was debugging some TI CC3100 WiFi firmware from an NXP ARM Cortex M4 device, and was probing the SPI bus running at 20MHz. Pretty soon I dropped into just using the logic analyser rather than the analog channels as it's easier to plug in the pod than mess with scope probes all the time. The scope is configured with the low speed serial data analyser and 64Mpts options, although the LA uses its own 32M samples per port memory. Now I may be wrong but the low speed serial option might be called low speed because it does take an awfully long time to update from either LA or analog channels. It's simple and quick to set up, but if you have a full buffer, real time updates are pretty much unusable. Using segmented acquisition judiciously helps here by reducing the amount of samples to interpret. There may be another way of setting it up of course, and I welcome any inout here. Having the serial data dialog box handy on the secondary monitor to disable and enable the decode helps a lot here. I noticed there's no RS232 decode, but maybe you can custom configure that.
Is the 54831D LA better than my Logicport? Well, the Logicport has 34 channels compared to the Agilent's 16, although I've only ever come close to using more than a dozen which was when I was debugging a parallel interface on an LCD display. The problem with the Logicport is that it runs out of memory very quickly, but it does do true real time serial decode and on a PC screen with a couple of 4k monitors you get to see an awful lot in one go. Where the 54831D wins is on its relatively massive 32M samples per channel on the LA whereas the Logicport only has a meagre 2048, although I should stress that it uses some fairly mean compression so it feels a lot more than 2048. However the biggest drawback of the Logicport is that it doesn't take much to find its buffer is just too small. Add to that the Agilent's segmented acquisition feature and it makes the Logicport seem a little quaint. However I have no intention of giving up the Logicport, it's served me very well for nearly ten years, and I expect it to continue to do so in certain situations.
Today I've been working on a high speed sample and hold (30Msps) using the scope's four analog channels and for that it's been awesome. My design suffers from some opamp instability that's taken me most of the afternoon to investigate, and this scope is just so much better for this than my old Tek. For reference, I measured the 3dB bandwidth with an RF signal generator on a 50 ohm channel and although it's quoted at 600MHz I was up to 820MHz before it hit the 3dB point. I was on a single channel, sampling at 4Gsps. It's the first time I've had a scope where you can see things sub nanosecond.
More generally although some folk aren't over keen on Windows on a scope, what's nice with a Windows based scope is being able to do mundane things like print a screenshot to your existing printers directly, or copy stuff to storage on your LAN without having to mess about with USB sticks.
On the downside, this scope has no fewer than six fans, so it's a noisy bugger. While it doesn't bother me too much, I am aware that some folks like their peace an quiet. Also, compared to the Tek, it's heavy and large. Both take a while to boot.
Now this second-hand ten year old 54831D cost just about the same as my brand new TDS2024B did maybe eight years or so ago. I realise the market's changed more recently with the likes of Rigol now being a serious contender at the TDS end of the market. However I would seriously recommend considering the second hand market before diving into a brand new scope.